a0747458e7
The HTTP PATCH method is now supported whereever HTTP methods are used. Annotated controllers can be mapped to RequestMethod.PATCH. On the client side the RestTemplate execute(..) and exchange(..) methods can be used with HttpMethod.PATCH. In terms of HTTP client libraries, Apache HttpComponents HttpClient version 4.2 or later is required (see HTTPCLIENT-1191). The JDK HttpURLConnection does not support the HTTP PATCH method. Issue: SPR-7985
4717 lines
217 KiB
XML
4717 lines
217 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xml:id="mvc">
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<title>Web MVC framework</title>
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<section id="mvc-introduction">
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<title>Introduction to Spring Web MVC framework</title>
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<para>The Spring Web model-view-controller (MVC) framework is designed
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around a <classname>DispatcherServlet</classname> that dispatches requests
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to handlers, with configurable handler mappings, view resolution, locale
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|
and theme resolution as well as support for uploading files. The default
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|
handler is based on the <interfacename>@Controller</interfacename> and
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<interfacename>@RequestMapping</interfacename> annotations, offering a
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wide range of flexible handling methods. With the introduction of Spring
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|
3.0, the <interfacename>@Controller</interfacename> mechanism also allows
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you to create RESTful Web sites and applications, through the
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<interfacename>@PathVariable</interfacename> annotation and other
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features.</para>
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<sidebar id="mvc-open-for-extension">
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<title><quote>Open for extension...</quote></title>
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<para>A key design principle in Spring Web MVC and in Spring in general
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is the <quote><emphasis>Open for extension, closed for
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modification</emphasis></quote> principle.</para>
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|
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<para>Some methods in the core classes of Spring Web MVC are marked
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<literal>final</literal>. As a developer you cannot override these
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methods to supply your own behavior. This has not been done arbitrarily,
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but specifically with this principle in mind.</para>
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|
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<para>For an explanation of this principle, refer to <emphasis>Expert
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Spring Web MVC and Web Flow</emphasis> by Seth Ladd and others;
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specifically see the section "A Look At Design," on page 117 of the
|
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first edition. Alternatively, see</para>
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|
|
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<orderedlist>
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<listitem>
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<para><ulink
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url="http://www.objectmentor.com/resources/articles/ocp.pdf">Bob
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|
Martin, The Open-Closed Principle (PDF)</ulink></para>
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</listitem>
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</orderedlist>
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<para>You cannot add advice to final methods when you use Spring MVC.
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For example, you cannot add advice to the
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<literal>AbstractController.setSynchronizeOnSession()</literal> method.
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Refer to <xref linkend="aop-understanding-aop-proxies" /> for more
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information on AOP proxies and why you cannot add advice to final
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methods.</para>
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</sidebar>
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<para>In Spring Web MVC you can use any object as a command or
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form-backing object; you do not need to implement a framework-specific
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interface or base class. Spring's data binding is highly flexible: for
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example, it treats type mismatches as validation errors that can be
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|
evaluated by the application, not as system errors. Thus you need not
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|
duplicate your business objects' properties as simple, untyped strings in
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your form objects simply to handle invalid submissions, or to convert the
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Strings properly. Instead, it is often preferable to bind directly to your
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business objects.</para>
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<para>Spring's view resolution is extremely flexible. A
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<interfacename>Controller</interfacename> is typically responsible for
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preparing a model <classname>Map</classname> with data and selecting a
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view name but it can also write directly to the response stream and
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complete the request. View name resolution is highly configurable through
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file extension or Accept header content type negotiation, through bean
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names, a properties file, or even a custom
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<interfacename>ViewResolver</interfacename> implementation. The model (the
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M in MVC) is a <interfacename>Map</interfacename> interface, which allows
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for the complete abstraction of the view technology. You can integrate
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directly with template based rendering technologies such as JSP, Velocity
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and Freemarker, or directly generate XML, JSON, Atom, and many other types
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of content. The model <interfacename>Map</interfacename> is simply
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transformed into an appropriate format, such as JSP request attributes, a
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Velocity template model.</para>
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<section id="mvc-features">
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<title>Features of Spring Web MVC<!--I moved Features of Spring Web MVC before Pluggability of other MVC implementations. You want to highlight your own imp. first.--></title>
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|
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|
<!--Second line of sidebar refers to JSF; don't you mean JSP? Other refs in this context are to JSP. Also note, sidebar is read-only.-->
|
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<xi:include href="swf-sidebar.xml"
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xmlns:xi="http://www.w3.org/2001/XInclude" />
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<para>Spring's web module includes many unique web support
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features:</para>
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|
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<itemizedlist>
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<listitem>
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<para><emphasis>Clear separation of roles</emphasis>. Each role —
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controller, validator, command object, form object, model object,
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<classname>DispatcherServlet</classname>, handler mapping, view
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resolver, and so on — can be fulfilled by a specialized
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object.</para>
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</listitem>
|
|
|
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<listitem>
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<para><emphasis>Powerful and straightforward configuration of both
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framework and application classes as JavaBeans</emphasis>. This
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|
configuration capability includes easy referencing across contexts,
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|
such as from web controllers to business objects and
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validators.</para>
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</listitem>
|
|
|
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<listitem>
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<para><emphasis>Adaptability, non-intrusiveness, and
|
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flexibility.</emphasis> Define any controller method signature you
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need, possibly using one of the parameter annotations (such as
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@RequestParam, @RequestHeader, @PathVariable, and more) for a given
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scenario.</para>
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</listitem>
|
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<listitem>
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<para><emphasis>Reusable business code</emphasis>,<emphasis> no need
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for duplication</emphasis>. Use existing business objects as command
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|
or form objects instead of mirroring them to extend a particular
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framework base class.</para>
|
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</listitem>
|
|
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<listitem>
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<para><emphasis>Customizable binding and validation</emphasis>. Type
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mismatches as application-level validation errors that keep the
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offending value, localized date and number binding, and so on
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instead of String-only form objects with manual parsing and
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conversion to business objects.</para>
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</listitem>
|
|
|
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<listitem>
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<para><emphasis>Customizable handler mapping and view
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resolution</emphasis>. Handler mapping and view resolution
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strategies range from simple URL-based configuration, to
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|
sophisticated, purpose-built resolution strategies. Spring is more
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flexible than web MVC frameworks that mandate a particular
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technique.</para>
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</listitem>
|
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<listitem>
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<para><emphasis>Flexible model transfer</emphasis>. Model transfer
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with a name/value <interfacename>Map</interfacename> supports easy
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integration with any view technology.</para>
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</listitem>
|
|
|
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<listitem>
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<para><emphasis>Customizable locale and theme resolution, support
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for JSPs with or without Spring tag library, support for JSTL,
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support for Velocity without the need for extra bridges, and so
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on.</emphasis></para>
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</listitem>
|
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<listitem>
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<para><emphasis>A simple yet powerful JSP tag library known as the
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Spring tag library that provides support for features such as data
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binding and themes</emphasis>. The custom tags allow for maximum
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|
flexibility in terms of markup code. For information on the tag
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|
library descriptor, see the appendix entitled <xref
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linkend="spring.tld" /></para>
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</listitem>
|
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<listitem>
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<para><emphasis>A JSP form tag library, introduced in Spring 2.0,
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that makes writing forms in JSP pages much easier.</emphasis> For
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information on the tag library descriptor, see the appendix entitled
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<xref linkend="spring-form.tld" /></para>
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</listitem>
|
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<listitem>
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<para><emphasis>Beans whose lifecycle is scoped to the current HTTP
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request or HTTP <interfacename>Session</interfacename>.</emphasis>
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This is not a specific feature of Spring MVC itself, but rather of
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the <interfacename>WebApplicationContext</interfacename>
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container(s) that Spring MVC uses. These bean scopes are described
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in <xref linkend="beans-factory-scopes-other" /></para>
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</listitem>
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</itemizedlist>
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</section>
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<section id="mvc-introduction-pluggability">
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<title>Pluggability of other MVC implementations</title>
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<para>Non-Spring MVC implementations are preferable for some projects.
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Many teams expect to leverage their existing investment in skills and
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tools. A large body of knowledge and experience exist for the Struts
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framework. If you can abide Struts' architectural flaws, it can be a
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|
viable choice for the web layer; the same applies to WebWork and other
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web MVC frameworks.</para>
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<para>If you do not want to use Spring's web MVC, but intend to leverage
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other solutions that Spring offers, you can integrate the web MVC
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|
framework of your choice with Spring easily. Simply start up a Spring
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root application context through its
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<classname>ContextLoaderListener</classname>, and access it through
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its<!--Identify *its*. do you mean root application context's?-->
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<interfacename>ServletContext</interfacename> attribute (or Spring's
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respective helper method) from within a Struts or WebWork action. No
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"plug-ins" are involved, so no dedicated integration is necessary. From
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|
the web layer's point of view, you simply use Spring as a library, with
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the root application context instance as the entry point.</para>
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<para>Your registered beans and Spring's services can be at your
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fingertips even without Spring's Web MVC. Spring does not compete with
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Struts or WebWork in this scenario. It simply addresses the many areas
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that the pure web MVC frameworks do not, from bean configuration to data
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access and transaction handling. So you can enrich your application with
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|
a Spring middle tier and/or data access tier, even if you just want to
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use, for example, the transaction abstraction with JDBC or
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Hibernate.</para>
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</section>
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</section>
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<section id="mvc-servlet">
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<title>The <classname>DispatcherServlet</classname></title>
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<para>Spring's web MVC framework is, like many other web MVC frameworks,
|
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request-driven, designed around a central Servlet that dispatches requests
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to controllers and offers other functionality that facilitates the
|
|
development of web applications. Spring's
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<classname>DispatcherServlet</classname> however, does more than just
|
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that. It is completely integrated with the Spring IoC container and as
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such allows you to use every other feature that Spring has.</para>
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<para>The request processing workflow of the Spring Web MVC
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<classname>DispatcherServlet</classname> is illustrated in the following
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|
diagram. The pattern-savvy reader will recognize that the
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|
<classname>DispatcherServlet</classname> is an expression of the
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<quote>Front Controller</quote> design pattern (this is a pattern that
|
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Spring Web MVC shares with many other leading web frameworks).</para>
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<para><mediaobject>
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<imageobject role="fo">
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<imagedata align="center" fileref="images/mvc.png" format="PNG"
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width="400" />
|
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</imageobject>
|
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|
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<imageobject role="html">
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<imagedata align="center" fileref="images/mvc.png" format="PNG" />
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</imageobject>
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<caption><para>The request processing workflow in Spring Web MVC (high
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level)</para></caption>
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</mediaobject></para>
|
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|
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<para>The <classname>DispatcherServlet</classname> is an actual
|
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<interfacename>Servlet</interfacename> (it inherits from the
|
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<classname>HttpServlet</classname> base class), and as such is declared in
|
|
the <literal>web.xml</literal> of your web application. You need to map
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requests that you want the <classname>DispatcherServlet</classname> to
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handle, by using a URL mapping in the same <literal>web.xml</literal>
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file. This is standard Java EE Servlet configuration; the following example
|
|
shows such a <classname>DispatcherServlet</classname> declaration and
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mapping:</para>
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<programlisting language="xml"><web-app>
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|
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<servlet>
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<servlet-name>example</servlet-name>
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<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
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<load-on-startup>1</load-on-startup>
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</servlet>
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|
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<servlet-mapping>
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<servlet-name>example</servlet-name>
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<url-pattern>/example/*</url-pattern>
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</servlet-mapping>
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|
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</web-app></programlisting>
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<para>In the preceding example, all requests starting with
|
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<literal>/example</literal> will be handled by the
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<classname>DispatcherServlet</classname> instance named
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<literal>example</literal>. This is only the first step in setting up
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Spring Web MVC. <!--The discussion below is a little vague about what you're doing, when you do it, and what you're accomplishing. --><!-- Is the next step shown in the next example screen?-->You
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now need to configure the various beans used by the Spring Web MVC
|
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framework (over and above the <classname>DispatcherServlet</classname>
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itself).<!--See previous sentence. Add info to indicate where you find info that tells you how to configure beans for MVC framework. --><!--Next paragraph, so what are you telling them to *do* here? --></para>
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<para>As detailed in <xref linkend="context-introduction" />,
|
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<interfacename>ApplicationContext</interfacename> instances in Spring can
|
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be scoped. In the Web MVC framework, each
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<classname>DispatcherServlet</classname> has its own
|
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<interfacename>WebApplicationContext</interfacename>, which inherits all
|
|
the beans already defined in the root
|
|
<interfacename>WebApplicationContext</interfacename>. These inherited
|
|
beans can be overridden in the servlet-specific scope, and you can define
|
|
new scope-specific beans local to a given Servlet instance.</para>
|
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|
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<para><mediaobject>
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<imageobject role="fo">
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<imagedata align="center" fileref="images/mvc-contexts.gif"
|
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format="GIF" width="400" />
|
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</imageobject>
|
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|
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<imageobject role="html">
|
|
<imagedata align="center" fileref="images/mvc-contexts.gif"
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format="GIF" />
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</imageobject>
|
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|
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<caption>Context hierarchy in Spring Web MVC</caption>
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</mediaobject></para>
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|
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<para>Upon initialization of a <classname>DispatcherServlet</classname>,
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Spring MVC looks for a file named <emphasis>
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<literal>[servlet-name]-servlet.xml</literal></emphasis> in the
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<literal>WEB-INF</literal> directory of your web application and creates
|
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the beans defined there, overriding the definitions of any beans defined
|
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with the same name in the global scope.</para>
|
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|
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<para>Consider the following <classname>DispatcherServlet</classname>
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Servlet configuration (in the <literal>web.xml</literal> file):</para>
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|
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<programlisting language="xml"><web-app>
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<servlet>
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<servlet-name><emphasis role="bold">golfing</emphasis></servlet-name>
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<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
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<load-on-startup>1</load-on-startup>
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</servlet>
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<servlet-mapping>
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<servlet-name><emphasis role="bold">golfing</emphasis></servlet-name>
|
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<url-pattern>/golfing/*</url-pattern>
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</servlet-mapping>
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|
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</web-app></programlisting>
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|
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<para>With the above Servlet configuration in place, <!--Is this something you need to do (in above example)? -->you
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will need to have a file called <literal>/WEB-INF/</literal><emphasis
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role="bold">golfing</emphasis><literal>-servlet.xml</literal> in your
|
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application; this file will contain all of your Spring Web MVC-specific
|
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components (beans). You can change the exact location of this
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configuration file through a Servlet initialization parameter (see below
|
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for details).</para>
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|
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<!--See *where* for details? Give x-ref to section talks about how to change the location of the file through servlet init. param.-->
|
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|
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<para>The <interfacename>WebApplicationContext</interfacename> is an
|
|
extension of the plain <interfacename>ApplicationContext</interfacename>
|
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that has some extra features necessary for web applications. It differs
|
|
from a normal <interfacename>ApplicationContext</interfacename> in that it
|
|
is capable of resolving themes (see <xref linkend="mvc-themeresolver" />),
|
|
and that it knows which Servlet it is associated with (by having a link to
|
|
the <interfacename>ServletContext</interfacename>). The
|
|
<interfacename>WebApplicationContext</interfacename> is bound in the
|
|
<interfacename>ServletContext</interfacename>, and by using static methods
|
|
on the <classname>RequestContextUtils</classname> class you can always
|
|
look up the <interfacename>WebApplicationContext</interfacename> if you
|
|
need access to it.</para>
|
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|
|
<section id="mvc-servlet-special-bean-types">
|
|
<title>Special Bean Types In the <interfacename>WebApplicationContext</interfacename></title>
|
|
|
|
<para>The Spring <classname>DispatcherServlet</classname> uses special
|
|
beans to process requests and render the appropriate views. These beans
|
|
are part of Spring MVC. You can choose which special beans to use
|
|
by simply configuring one or more of them in the
|
|
<interfacename>WebApplicationContext</interfacename>.
|
|
However, you don't need to do that initially since Spring MVC
|
|
maintains a list of default beans to use if you don't configure any.
|
|
More on that in the next section. First see the table below
|
|
listing the special bean types the
|
|
<classname>DispatcherServlet</classname> relies on.</para>
|
|
|
|
<table id="mvc-webappctx-special-beans-tbl">
|
|
<title>Special bean types in the
|
|
<interfacename>WebApplicationContext</interfacename></title>
|
|
|
|
<tgroup cols="2">
|
|
<colspec colname="c1" colwidth="1*" />
|
|
|
|
<colspec colname="c2" colwidth="4*" />
|
|
|
|
<thead>
|
|
<row>
|
|
<entry>Bean type</entry>
|
|
|
|
<entry>Explanation</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><link linkend="mvc-handlermapping">HandlerMapping</link></entry>
|
|
|
|
<entry>Maps incoming requests to handlers and a list of
|
|
pre- and post-processors (handler interceptors) based on some
|
|
criteria the details of which vary by <interfacename>HandlerMapping</interfacename>
|
|
implementation. The most popular implementation supports
|
|
annotated controllers but other implementations exists as well.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>HandlerAdapter</entry>
|
|
|
|
<entry>Helps the <interfacename>DispatcherServlet</interfacename> to
|
|
invoke a handler mapped to a request regardless of the handler
|
|
is actually invoked. For example, invoking an annotated controller
|
|
requires resolving various annotations. Thus the main purpose
|
|
of a <interfacename>HandlerAdapter</interfacename> is to shield the
|
|
<classname>DispatcherServlet</classname> from such details.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><link linkend="mvc-exceptionhandlers">HandlerExceptionResolver</link></entry>
|
|
|
|
<entry>Maps exceptions to views also allowing for more
|
|
complex exception handling code.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><link linkend="mvc-viewresolver">ViewResolver</link></entry>
|
|
|
|
<entry>Resolves logical String-based view names to actual
|
|
<interface>View</interface> types.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><link linkend="mvc-localeresolver">LocaleResolver</link></entry>
|
|
|
|
<entry>Resolves the locale a client is using,
|
|
in order to be able to offer internationalized views</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><link linkend="mvc-themeresolver">ThemeResolver</link></entry>
|
|
|
|
<entry>Resolves themes your web application can use, for
|
|
example, to offer personalized layouts</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><link linkend="mvc-multipart">MultipartResolver</link></entry>
|
|
|
|
<entry>Parses multi-part requests for example to support processing
|
|
file uploads from HTML forms.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><link linkend="mvc-flash-attributes">FlashMapManager</link></entry>
|
|
|
|
<entry>Stores and retrieves the "input" and the "output"
|
|
<classname>FlashMap</classname> that can be used to pass attributes
|
|
from one request to another, usually across a redirect.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
</section>
|
|
|
|
<section id="mvc-servlet-config">
|
|
<title>Default DispatcherServlet Configuration</title>
|
|
|
|
<para>As mentioned in the previous section for each special bean
|
|
the <classname>DispatcherServlet</classname> maintains a list
|
|
of implementations to use by default. This information is
|
|
kept in the file <filename>DispatcherServlet.properties</filename>
|
|
in the package <classname>org.springframework.web.servlet</classname>.
|
|
</para>
|
|
|
|
<para>All special beans have some reasonable defaults of
|
|
their own. Sooner or later though you'll need to customize
|
|
one or more of the properties these beans provide.
|
|
For example it's quite common to configure
|
|
an <classname>InternalResourceViewResolver</classname>
|
|
settings its <literal>prefix</literal> property to
|
|
the parent location of view files.</para>
|
|
|
|
<para>Regardless of the details, the important concept
|
|
to understand here is that once
|
|
you configure a special bean such as an
|
|
<classname>InternalResourceViewResolver</classname>
|
|
in your <classname>WebApplicationContext</classname>, you
|
|
effectively override the list of default implementations
|
|
that would have been used otherwise for that special bean
|
|
type. For example if you configure an
|
|
<classname>InternalResourceViewResolver</classname>,
|
|
the default list of <interfacename>ViewResolver</interfacename>
|
|
implementations is ignored.
|
|
</para>
|
|
|
|
<para>In <xref linkend="mvc-config"/> you'll learn about
|
|
other options for configuring Spring MVC including
|
|
MVC Java config and the MVC XML namespace both of which provide
|
|
a simple starting point and assume little knowledge of
|
|
how Spring MVC works. Regardless of how you choose to
|
|
configure your application, the concepts explained in this
|
|
section are fundamental should be of help to you.
|
|
</para>
|
|
|
|
</section>
|
|
|
|
<section id="mvc-servlet-sequence">
|
|
<title>DispatcherServlet Processing Sequence</title>
|
|
|
|
<para>After you set up a <classname>DispatcherServlet</classname>, and a
|
|
request comes in for that specific
|
|
<classname>DispatcherServlet</classname>, the
|
|
<classname>DispatcherServlet</classname> starts processing the request as
|
|
follows:</para>
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>The <interfacename>WebApplicationContext</interfacename> is
|
|
searched for and bound in the request as an attribute that the
|
|
controller and other elements in the process can use. <!--Use to do *what*? Also revise to indicate *what* searches for the WebApplicationContext -->It
|
|
is bound by default under the key
|
|
<literal>DispatcherServlet.WEB_APPLICATION_CONTEXT_ATTRIBUTE</literal>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The locale resolver is bound to the request to enable elements
|
|
in the process to resolve the locale to use when processing the
|
|
request (rendering the view, preparing data, and so on). If you do not
|
|
need locale resolving, you do not need it.</para>
|
|
|
|
<!--Reword 'if you don't need local resolving, you don't need to use it '. Are you saying locale resolving is optional? If you don't configure it, will this step occur?-->
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The theme resolver is bound to the request to let elements such
|
|
as views determine which theme to use. If you do not use themes, you
|
|
can ignore it.</para>
|
|
|
|
<!-- MLP perhaps say that there are not side effect to this binding, etc... Clarify *ignore it*. Does this step still occur if you don't use themes? -->
|
|
|
|
<!--And what if you DO use themes, what do you do and when? Same question re locale resolving.-->
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If you specify a multipart file resolver, the request is
|
|
inspected for multiparts; if multiparts are found, the request is
|
|
wrapped in a <classname>MultipartHttpServletRequest</classname> for
|
|
further processing by other elements in the process. See <xref
|
|
linkend="mvc-multipart" /> for further information about multipart
|
|
handling.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An appropriate handler is searched for. If a handler is found,
|
|
the execution chain associated with the handler (preprocessors,
|
|
postprocessors, and controllers) is executed in order to prepare a
|
|
model or rendering.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If a model is returned, the view is rendered. If no model is
|
|
returned, (may be due to a preprocessor or postprocessor intercepting
|
|
the request, perhaps for security reasons), no view is rendered,
|
|
because the request could already have been fulfilled.</para>
|
|
|
|
<!--fulfilled how and by what?-->
|
|
</listitem>
|
|
</orderedlist>
|
|
|
|
<para>Handler exception resolvers that are declared in the
|
|
<interfacename>WebApplicationContext</interfacename> pick up exceptions
|
|
that are thrown during processing of the request. Using these exception
|
|
resolvers allows you to define custom behaviors to address
|
|
exceptions.</para>
|
|
|
|
</section>
|
|
|
|
<para>The Spring <classname>DispatcherServlet</classname> also supports
|
|
the return of the <emphasis>last-modification-date</emphasis>, as
|
|
specified by the Servlet API. The process of determining the last
|
|
modification date for a specific request is straightforward: the
|
|
<classname>DispatcherServlet</classname> looks up an appropriate handler
|
|
mapping and tests whether the handler that is found implements the
|
|
<emphasis><interfacename>LastModified</interfacename></emphasis>
|
|
interface. If so, the value of the <literal>long
|
|
getLastModified(request)</literal> method of the
|
|
<interfacename>LastModified</interfacename> interface is returned to the
|
|
client.</para>
|
|
|
|
<para>You can customize individual
|
|
<classname>DispatcherServlet</classname> instances by adding Servlet
|
|
initialization parameters (<literal>init-param</literal> elements) to the
|
|
Servlet declaration in the <literal>web.xml</literal> file. See the
|
|
following table for the list of supported parameters.</para>
|
|
|
|
<!--Reword above sentence to specify whether configuring parameters in table configures last-modification-date, or are they further -->
|
|
|
|
<!--customization for some other purpose? If so, need to explain how you config last-modification-date-->
|
|
|
|
<table id="mvc-disp-servlet-init-params-tbl">
|
|
<title><classname>DispatcherServlet</classname> initialization
|
|
parameters</title>
|
|
|
|
<tgroup cols="2">
|
|
<colspec colname="c1" colwidth="1*" />
|
|
|
|
<colspec colname="c2" colwidth="4*" />
|
|
|
|
<thead>
|
|
<row>
|
|
<entry>Parameter</entry>
|
|
|
|
<entry>Explanation</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><literal>contextClass</literal></entry>
|
|
|
|
<entry>Class that implements
|
|
<interfacename>WebApplicationContext</interfacename>, which
|
|
instantiates the context used by this Servlet. By default, the
|
|
<classname>XmlWebApplicationContext</classname> is used.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>contextConfigLocation</literal></entry>
|
|
|
|
<entry>String that is passed to the context instance (specified by
|
|
<literal>contextClass</literal>) to indicate where context(s) can
|
|
be found. The string consists potentially of multiple strings
|
|
(using a comma as a delimiter) to support multiple contexts. In
|
|
case of multiple context locations with beans that are defined
|
|
twice, the latest location takes precedence.</entry>
|
|
|
|
<!-- MLP review -->
|
|
</row>
|
|
|
|
<row>
|
|
<entry><literal>namespace</literal></entry>
|
|
|
|
<entry>Namespace of the
|
|
<interfacename>WebApplicationContext</interfacename>. Defaults to
|
|
<literal>[servlet-name]-servlet</literal>.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</section>
|
|
|
|
<section id="mvc-controller">
|
|
<title>Implementing Controllers</title>
|
|
|
|
<para>Controllers provide access to the application behavior that you
|
|
typically define through a service interface. <!--I changed preceding to active voice because next sentence refers to user input. Thus *you* do some defining.-->Controllers
|
|
interpret user input and transform it into a model that is represented to
|
|
the user by the view. Spring implements a controller in a very abstract
|
|
way, which enables you to create a wide variety of controllers.</para>
|
|
|
|
<para>Spring 2.5 introduced an annotation-based programming model for MVC
|
|
controllers that uses annotations such as
|
|
<interfacename>@RequestMapping</interfacename>,
|
|
<interfacename>@RequestParam</interfacename>,
|
|
<interfacename>@ModelAttribute</interfacename>, and so on. This annotation
|
|
support is available for both Servlet MVC and Portlet MVC. Controllers
|
|
implemented in this style do not have to extend specific base classes or
|
|
implement specific interfaces. Furthermore, they do not usually have
|
|
direct dependencies on Servlet or Portlet APIs, although you can easily
|
|
configure access to Servlet or Portlet facilities.</para>
|
|
|
|
<tip>
|
|
<para>Available in the <link linkend="new-in-3.0-samples">samples
|
|
repository</link>, a number of web applications leverage the annotation
|
|
support described in this section including
|
|
<emphasis>MvcShowcase</emphasis>, <emphasis>MvcAjax</emphasis>,
|
|
<emphasis>MvcBasic</emphasis>, <emphasis>PetClinic</emphasis>,
|
|
<emphasis>PetCare</emphasis>, and others.</para>
|
|
|
|
<!-- MLP Note removed reference to imagedb -->
|
|
</tip>
|
|
|
|
<!--You need an intro sentence here that indicates the *purpose* of the following code. -->
|
|
|
|
<programlisting language="java">@Controller
|
|
public class HelloWorldController {
|
|
|
|
@RequestMapping("/helloWorld")
|
|
public String helloWorld(Model model) {
|
|
model.addAttribute("message", "Hello World!");
|
|
return "helloWorld";
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>As you can see, the <interfacename>@Controller</interfacename> and
|
|
<interfacename>@RequestMapping</interfacename> annotations allow flexible
|
|
method names and signatures. In this particular example the method accepts
|
|
a <classname>Model</classname> and returns a view name as a
|
|
<classname>String</classname>, but various other method parameters and
|
|
return values can be used as explained later in this section.
|
|
<interfacename>@Controller</interfacename> and
|
|
<interfacename>@RequestMapping</interfacename> and a number of other
|
|
annotations form the basis for the Spring MVC implementation. This section
|
|
documents these annotations and how they are most commonly used in a
|
|
Servlet environment.</para>
|
|
|
|
<section id="mvc-ann-controller">
|
|
<title>Defining a controller with
|
|
<interfacename>@Controller</interfacename></title>
|
|
|
|
<para>The <interfacename>@Controller</interfacename> annotation
|
|
indicates that a particular class serves the role of a
|
|
<emphasis>controller</emphasis>. Spring does not require you to extend
|
|
any controller base class or reference the Servlet API. However, you can
|
|
still reference Servlet-specific features if you need to.</para>
|
|
|
|
<para>The <interfacename>@Controller</interfacename> annotation acts as
|
|
a stereotype for the annotated class, indicating its role. The
|
|
dispatcher scans such annotated classes for mapped methods and detects
|
|
<interfacename>@RequestMapping</interfacename> annotations (see the next
|
|
section).</para>
|
|
|
|
<para>You can define annotated controller beans explicitly, using a
|
|
standard Spring bean definition in the dispatcher's context. However,
|
|
the <interfacename>@Controller</interfacename> stereotype also allows
|
|
for autodetection, aligned with Spring general support for detecting
|
|
component classes in the classpath and auto-registering bean definitions
|
|
for them.</para>
|
|
|
|
<!-- MLP Bev.changed to 'also supports autodetection -->
|
|
|
|
<para>To enable autodetection of such annotated controllers, you add
|
|
component scanning to your configuration. Use the
|
|
<emphasis>spring-context</emphasis> schema as shown in the following XML
|
|
snippet:</para>
|
|
|
|
<programlisting language="xml"><?xml version="1.0" encoding="UTF-8"?>
|
|
<beans xmlns="http://www.springframework.org/schema/beans"
|
|
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
|
xmlns:p="http://www.springframework.org/schema/p"
|
|
xmlns:context="http://www.springframework.org/schema/context"
|
|
xsi:schemaLocation="
|
|
http://www.springframework.org/schema/beans
|
|
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
|
|
http://www.springframework.org/schema/context
|
|
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
|
|
|
|
<context:component-scan base-package="org.springframework.samples.petclinic.web"/>
|
|
|
|
<lineannotation><!-- ... --></lineannotation>
|
|
|
|
</beans></programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping">
|
|
<title>Mapping Requests With
|
|
<interfacename>@RequestMapping</interfacename></title>
|
|
|
|
<para>You use the <interfacename>@RequestMapping</interfacename>
|
|
annotation to map URLs such as <filename>/appointments</filename> onto
|
|
an entire class or a particular handler method. Typically the
|
|
class-level annotation maps a specific request path (or path pattern)
|
|
onto a form controller, with additional method-level annotations
|
|
narrowing the primary mapping for a specific HTTP method request method
|
|
("GET", "POST", etc.) or an HTTP request parameter condition.</para>
|
|
|
|
<para>The following example from the <emphasis>Petcare</emphasis> sample
|
|
shows a controller in a Spring MVC application that uses this
|
|
annotation:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
<emphasis role="bold">@RequestMapping("/appointments")</emphasis>
|
|
public class AppointmentsController {
|
|
|
|
private final AppointmentBook appointmentBook;
|
|
|
|
@Autowired
|
|
public AppointmentsController(AppointmentBook appointmentBook) {
|
|
this.appointmentBook = appointmentBook;
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping(method = RequestMethod.GET)</emphasis>
|
|
public Map<String, Appointment> get() {
|
|
return appointmentBook.getAppointmentsForToday();
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping(value="/{day}", method = RequestMethod.GET)</emphasis>
|
|
public Map<String, Appointment> getForDay(@PathVariable @DateTimeFormat(iso=ISO.DATE) Date day, Model model) {
|
|
return appointmentBook.getAppointmentsForDay(day);
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping(value="/new", method = RequestMethod.GET)</emphasis>
|
|
public AppointmentForm getNewForm() {
|
|
return new AppointmentForm();
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping(method = RequestMethod.POST)</emphasis>
|
|
public String add(@Valid AppointmentForm appointment, BindingResult result) {
|
|
if (result.hasErrors()) {
|
|
return "appointments/new";
|
|
}
|
|
appointmentBook.addAppointment(appointment);
|
|
return "redirect:/appointments";
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>In the example, the <interfacename>@RequestMapping</interfacename>
|
|
is used in a number of places. The first usage is on the type (class)
|
|
level, which indicates that all handling methods on this controller are
|
|
relative to the <filename>/appointments</filename> path. The
|
|
<methodname>get()</methodname> method has a further
|
|
<interfacename>@RequestMapping</interfacename> refinement: it only
|
|
accepts GET requests, meaning that an HTTP GET for
|
|
<filename>/appointments</filename> invokes this method. The
|
|
<methodname>post()</methodname> has a similar refinement, and the
|
|
<methodname>getNewForm()</methodname> combines the definition of HTTP
|
|
method and path into one, so that GET requests for
|
|
<filename>appointments/new</filename> are handled by that method.</para>
|
|
|
|
<para>The <methodname>getForDay()</methodname> method shows another
|
|
usage of <interfacename>@RequestMapping</interfacename>: URI templates.
|
|
(See <link linkend="mvc-ann-requestmapping-uri-templates">the next
|
|
section </link>).</para>
|
|
|
|
<para>A <interfacename>@RequestMapping</interfacename> on the class
|
|
level is not required. Without it, all paths are simply absolute, and
|
|
not relative. The following example from the
|
|
<emphasis>PetClinic</emphasis> sample application shows a multi-action
|
|
controller using <classname>@RequestMapping</classname>:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class ClinicController {
|
|
|
|
private final Clinic clinic;
|
|
|
|
@Autowired
|
|
public ClinicController(Clinic clinic) {
|
|
this.clinic = clinic;
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping("/")</emphasis>
|
|
public void welcomeHandler() {
|
|
}
|
|
|
|
<emphasis role="bold">@RequestMapping("/vets")</emphasis>
|
|
public ModelMap vetsHandler() {
|
|
return new ModelMap(this.clinic.getVets());
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<tip>
|
|
<title>Using <interfacename>@RequestMapping</interfacename> On
|
|
Interface Methods</title>
|
|
|
|
<para>A common pitfall when working with annotated controller classes
|
|
happens when applying functionality that requires creating a proxy for
|
|
the controller object (e.g.
|
|
<interfacename>@Transactional</interfacename> methods). Usually you
|
|
will introduce an interface for the controller in order to use JDK
|
|
dynamic proxies. To make this work you must move the
|
|
<interfacename>@RequestMapping</interfacename> annotations to the
|
|
interface as well as the mapping mechanism can only "see" the
|
|
interface exposed by the proxy. Alternatively, you could activate
|
|
<code>proxy-target-class="true"</code> in the configuration for the
|
|
functionality applied to the controller (in our transaction scenario
|
|
in <code><tx:annotation-driven /></code>). Doing so indicates
|
|
that CGLIB-based subclass proxies should be used instead of
|
|
interface-based JDK proxies. For more information on various proxying
|
|
mechanisms see <xref linkend="aop-proxying" />.</para>
|
|
</tip>
|
|
|
|
<section id="mvc-ann-requestmapping-31-vs-30">
|
|
<title>New Support Classes for <classname>@RequestMapping</classname> methods in Spring MVC 3.1</title>
|
|
|
|
<para>Spring 3.1 introduced a new set of support classes for
|
|
<classname>@RequestMapping</classname> methods called
|
|
<classname>RequestMappingHandlerMapping</classname> and
|
|
<classname>RequestMappingHandlerAdapter</classname> respectively.
|
|
They are recommended for use and even required to take advantage of
|
|
new features in Spring MVC 3.1 and going forward. The new support
|
|
classes are enabled by default by the MVC namespace and MVC Java
|
|
config (<classname>@EnableWebMvc</classname>) but must be configured
|
|
explicitly if using neither. This section describes a few
|
|
important differences between the old and the new support classes.
|
|
</para>
|
|
|
|
<para>Prior to Spring 3.1, type and method-level request mappings were
|
|
examined in two separate stages -- a controller was selected first
|
|
by the <classname>DefaultAnnotationHandlerMapping</classname> and the
|
|
actual method to invoke was narrowed down second by
|
|
the <classname>AnnotationMethodHandlerAdapter</classname>.</para>
|
|
|
|
<para>With the new support classes in Spring 3.1, the
|
|
<classname>RequestMappingHandlerMapping</classname> is the only place
|
|
where a decision is made about which method should process the request.
|
|
Think of controller methods as a collection of unique endpoints
|
|
with mappings for each method derived from type and method-level
|
|
<classname>@RequestMapping</classname> information.</para>
|
|
|
|
<para>This enables some new possibilities. For once a
|
|
<classname>HandlerInterceptor</classname> or a
|
|
<classname>HandlerExceptionResolver</classname> can now expect the
|
|
Object-based handler to be a <classname>HandlerMethod</classname>,
|
|
which allows them to examine the exact method, its parameters and
|
|
associated annotations. The processing for a URL no longer needs to
|
|
be split across different controllers.
|
|
</para>
|
|
|
|
<para>There are also several things no longer possible:</para>
|
|
<itemizedlist>
|
|
<listitem><para>Select a controller first with a
|
|
<classname>SimpleUrlHandlerMapping</classname> or
|
|
<classname>BeanNameUrlHandlerMapping</classname> and then narrow
|
|
the method based on <classname>@RequestMapping</classname>
|
|
annotations.</para></listitem>
|
|
<listitem><para>Rely on method names as a fall-back mechanism to
|
|
disambiguate between two <classname>@RequestMapping</classname> methods
|
|
that don't have an explicit path mapping URL path but otherwise
|
|
match equally, e.g. by HTTP method. In the new support classes
|
|
<classname>@RequestMapping</classname> methods have to be mapped
|
|
uniquely.</para></listitem>
|
|
<listitem><para>Have a single default method (without an explicit
|
|
path mapping) with which requests are processed if no other
|
|
controller method matches more concretely. In the new support
|
|
classes if a matching method is not found a 404 error
|
|
is raised.</para></listitem>
|
|
</itemizedlist>
|
|
|
|
<para>The above features are still supported with the existing support
|
|
classes. However to take advantage of new Spring MVC 3.1 features
|
|
you'll need to use the new support classes.</para>
|
|
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping-uri-templates">
|
|
<title>URI Template Patterns</title>
|
|
|
|
<para><emphasis>URI templates</emphasis> can be used for convenient
|
|
access to selected parts of a URL in a
|
|
<interfacename>@RequestMapping</interfacename> method.</para>
|
|
|
|
<para>A URI Template is a URI-like string, containing one or more
|
|
variable names. When you substitute values for these variables, the
|
|
template becomes a URI. The <ulink
|
|
url="http://bitworking.org/projects/URI-Templates/">proposed
|
|
RFC</ulink> for URI Templates defines how a URI is parameterized. For
|
|
example, the URI Template
|
|
<code>http://www.example.com/users/{userId}</code> contains the
|
|
variable <emphasis>userId</emphasis>. Assigning the value
|
|
<emphasis>fred</emphasis> to the variable yields
|
|
<code>http://www.example.com/users/fred</code>.</para>
|
|
|
|
<para>In Spring MVC you can use the
|
|
<interfacename>@PathVariable</interfacename> annotation on a method
|
|
argument to bind it to the value of a URI template variable:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value="/owners/{ownerId}", method=RequestMethod.GET)
|
|
public String findOwner(<emphasis role="bold">@PathVariable</emphasis> String ownerId, Model model) {
|
|
Owner owner = ownerService.findOwner(ownerId);
|
|
model.addAttribute("owner", owner);
|
|
return "displayOwner";
|
|
}</programlisting>
|
|
|
|
<para>The URI Template "<literal>/owners/{ownerId}</literal>"
|
|
specifies the variable name <literal>ownerId</literal>. When the
|
|
controller handles this request, the value of
|
|
<literal>ownerId</literal> is set to the value found in the
|
|
appropriate part of the URI. For example, when a request comes in for
|
|
<code>/owners/fred</code>, the value of <literal>ownerId</literal> is
|
|
<literal>fred</literal>.</para>
|
|
|
|
<tip>
|
|
<para>To process the @PathVariable annotation, Spring MVC needs to
|
|
find the matching URI template variable by name. You can specify it
|
|
in the annotation:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value="/owners/{ownerId}", method=RequestMethod.GET)
|
|
public String findOwner(<emphasis role="bold">@PathVariable</emphasis>("ownerId") String theOwner, Model model) {
|
|
// implementation omitted
|
|
}</programlisting>
|
|
|
|
<para>Or if the URI template variable name matches the method
|
|
argument name you can omit that detail. As long as your code is not
|
|
compiled without debugging information, Spring MVC will match the
|
|
method argument name to the URI template variable name:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value="/owners/{ownerId}", method=RequestMethod.GET)
|
|
public String findOwner(<emphasis role="bold">@PathVariable</emphasis> String ownerId, Model model) {
|
|
// implementation omitted
|
|
}</programlisting>
|
|
</tip>
|
|
|
|
<para>A method can have any number of
|
|
<interfacename>@PathVariable</interfacename> annotations:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value="/owners/{ownerId}/pets/{petId}", method=RequestMethod.GET)
|
|
public String findPet(<emphasis role="bold">@PathVariable</emphasis> String ownerId, <emphasis
|
|
role="bold">@PathVariable</emphasis> String petId, Model model) {
|
|
Owner owner = ownerService.findOwner(ownerId);
|
|
Pet pet = owner.getPet(petId);
|
|
model.addAttribute("pet", pet);
|
|
return "displayPet";
|
|
}</programlisting>
|
|
|
|
<para>When a <interfacename>@PathVariable</interfacename> annotation is
|
|
used on a <classname>Map<String, String></classname> argument, the
|
|
map is populated with all URI template variables.
|
|
</para>
|
|
|
|
<para>A URI template can be assembled from type and path level
|
|
<emphasis>@RequestMapping</emphasis> annotations. As a result the
|
|
<methodname>findPet()</methodname> method can be invoked with a URL
|
|
such as <filename>/owners/42/pets/21</filename>.</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping(<emphasis role="bold">"/owners/{ownerId}"</emphasis>)
|
|
public class RelativePathUriTemplateController {
|
|
|
|
@RequestMapping(<emphasis role="bold">"/pets/{petId}"</emphasis>)
|
|
public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {
|
|
// implementation omitted
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>A <interfacename>@PathVariable</interfacename> argument can be
|
|
of <emphasis role="bold">any simple type</emphasis> such as int, long,
|
|
Date, etc. Spring automatically converts to the appropriate type or
|
|
throws a <classname>TypeMismatchException</classname> if it fails to
|
|
do so. You can also register support for parsing additional data
|
|
types. See <xref linkend="mvc-ann-typeconversion" /> and <xref
|
|
linkend="mvc-ann-webdatabinder" />.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping-uri-templates-regex">
|
|
<title>URI Template Patterns with Regular Expressions</title>
|
|
|
|
<para>Sometimes you need more precision in defining URI template
|
|
variables. Consider the URL
|
|
<code>"/spring-web/spring-web-3.0.5.jar"</code>. How do you break it
|
|
down into multiple parts?</para>
|
|
|
|
<para>The <interfacename>@RequestMapping</interfacename> annotation
|
|
supports the use of regular expressions in URI template variables. The
|
|
syntax is <code>{varName:regex}</code> where the first part defines
|
|
the variable name and the second - the regular expression.For
|
|
example:</para>
|
|
|
|
<programlisting language="java">
|
|
@RequestMapping("/spring-web/{symbolicName:[a-z-]+}-{version:\d\.\d\.\d}.{extension:\.[a-z]}")
|
|
public void handle(@PathVariable String version, @PathVariable String extension) {
|
|
// ...
|
|
}
|
|
}</programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping-patterns">
|
|
<title>Path Patterns</title>
|
|
|
|
<para>In addition to URI templates, the
|
|
<interfacename>@RequestMapping</interfacename> annotation also
|
|
supports Ant-style path patterns (for example,
|
|
<filename>/myPath/*.do</filename>). A combination of URI templates and
|
|
Ant-style globs is also supported (for example,
|
|
<filename>/owners/*/pets/{petId}</filename>).</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping-consumes">
|
|
<title>Consumable Media Types</title>
|
|
|
|
<para>You can narrow the primary mapping by specifying a list of
|
|
consumable media types. The request will be matched only if the
|
|
<emphasis>Content-Type</emphasis> request header matches the specified
|
|
media type. For example:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping(value = "/pets", method = RequestMethod.POST, <emphasis
|
|
role="bold">consumes="application/json"</emphasis>)
|
|
public void addPet(@RequestBody Pet pet, Model model) {
|
|
// implementation omitted
|
|
}</programlisting>
|
|
|
|
<para>Consumable media type expressions can also be negated as in
|
|
<emphasis>!text/plain</emphasis> to match to all requests other than
|
|
those with <emphasis>Content-Type</emphasis> of
|
|
<emphasis>text/plain</emphasis>.</para>
|
|
|
|
<tip>
|
|
<para>The <emphasis>consumes</emphasis> condition is supported on
|
|
the type and on the method level. Unlike most other conditions, when
|
|
used at the type level, method-level consumable types override
|
|
rather than extend type-level consumable types.</para>
|
|
</tip>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping-produces">
|
|
<title>Producible Media Types</title>
|
|
|
|
<para>You can narrow the primary mapping by specifying a list of
|
|
producible media types. The request will be matched only if the
|
|
<emphasis>Accept</emphasis> request header matches one of these
|
|
values. Furthermore, use of the <emphasis>produces</emphasis>
|
|
condition ensures the actual content type used to generate the
|
|
response respects the media types specified in the
|
|
<emphasis>produces</emphasis> condition. For example:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, <emphasis
|
|
role="bold">produces="application/json"</emphasis>)
|
|
@ResponseBody
|
|
public Pet getPet(@PathVariable String petId, Model model) {
|
|
// implementation omitted
|
|
}</programlisting>
|
|
|
|
<para>Just like with <emphasis>consumes</emphasis>, producible media
|
|
type expressions can be negated as in <emphasis>!text/plain</emphasis>
|
|
to match to all requests other than those with an
|
|
<emphasis>Accept</emphasis> header value of
|
|
<emphasis>text/plain</emphasis>.</para>
|
|
|
|
<tip>
|
|
<para>The <emphasis>produces</emphasis> condition is supported on
|
|
the type and on the method level. Unlike most other conditions, when
|
|
used at the type level, method-level producible types override
|
|
rather than extend type-level producible types.</para>
|
|
</tip>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestmapping-params-and-headers">
|
|
<title>Request Parameters and Header Values</title>
|
|
|
|
<para>You can narrow request matching through request parameter
|
|
conditions such as <code>"myParam"</code>, <code>"!myParam"</code>, or
|
|
<code>"myParam=myValue"</code>. The first two test for request
|
|
parameter presence/absence and the third for a specific parameter
|
|
value. Here is an example with a request parameter value
|
|
condition:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping("/owners/{ownerId}")
|
|
public class RelativePathUriTemplateController {
|
|
|
|
@RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, <emphasis
|
|
role="bold">params="myParam=myValue"</emphasis>)
|
|
public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {
|
|
// implementation omitted
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>The same can be done to test for request header presence/absence
|
|
or to match based on a specific request header value:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping("/owners/{ownerId}")
|
|
public class RelativePathUriTemplateController {
|
|
|
|
@RequestMapping(value = "/pets", method = RequestMethod.GET, <emphasis
|
|
role="bold">headers="myHeader=myValue"</emphasis>)
|
|
public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {
|
|
// implementation omitted
|
|
}
|
|
}</programlisting>
|
|
|
|
<tip>
|
|
<para>Although you can match to <emphasis>Content-Type</emphasis>
|
|
and <emphasis>Accept</emphasis> header values using media type wild
|
|
cards (for example <emphasis>"content-type=text/*"</emphasis> will
|
|
match to <emphasis>"text/plain"</emphasis> and
|
|
<emphasis>"text/html"</emphasis>), it is recommended to use the
|
|
<emphasis>consumes</emphasis> and <emphasis>produces</emphasis>
|
|
conditions respectively instead. They are intended specifically for
|
|
that purpose.</para>
|
|
</tip>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-ann-methods">
|
|
<title>Defining <interface>@RequestMapping</interface> handler
|
|
methods</title>
|
|
|
|
<para>An <classname>@RequestMapping</classname> handler method can have
|
|
a very flexible signatures. The supported method arguments and return
|
|
values are described in the following section. Most arguments can be
|
|
used in arbitrary order with the only exception of
|
|
<classname>BindingResult</classname> arguments. This is described in the
|
|
next section.</para>
|
|
|
|
<note><para>Spring 3.1 introduced a new set of support classes for
|
|
<classname>@RequestMapping</classname> methods called
|
|
<classname>RequestMappingHandlerMapping</classname> and
|
|
<classname>RequestMappingHandlerAdapter</classname> respectively.
|
|
They are recommended for use and even required to take advantage
|
|
of new features in Spring MVC 3.1 and going forward.
|
|
The new support classes are enabled by default from the MVC namespace and
|
|
with use of the MVC Java config (<code>@EnableWebMvc</code>) but must be
|
|
configured explicitly if using neither.
|
|
</para></note>
|
|
|
|
<section id="mvc-ann-arguments">
|
|
<title>Supported method argument types</title>
|
|
|
|
<para>The following are the supported method arguments: <itemizedlist>
|
|
<listitem>
|
|
<para>Request or response objects (Servlet API). Choose any
|
|
specific request or response type, for example
|
|
<interfacename>ServletRequest</interfacename> or
|
|
<interfacename>HttpServletRequest</interfacename>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Session object (Servlet API): of type
|
|
<interfacename>HttpSession</interfacename>. An argument of this
|
|
type enforces the presence of a corresponding session. As a
|
|
consequence, such an argument is never
|
|
<literal>null</literal>.</para>
|
|
|
|
<note>
|
|
<para>Session access may not be thread-safe, in particular in
|
|
a Servlet environment. Consider setting the
|
|
<classname>RequestMappingHandlerAdapter</classname>'s
|
|
"synchronizeOnSession" flag to "true" if multiple requests are
|
|
allowed to access a session concurrently.</para>
|
|
</note>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>org.springframework.web.context.request.WebRequest</classname>
|
|
or
|
|
<classname>org.springframework.web.context.request.NativeWebRequest</classname>.
|
|
Allows for generic request parameter access as well as
|
|
request/session attribute access, without ties to the native
|
|
Servlet/Portlet API.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>java.util.Locale</classname> for the current
|
|
request locale, determined by the most specific locale resolver
|
|
available, in effect, the configured
|
|
<interfacename>LocaleResolver</interfacename> in a Servlet
|
|
environment.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>java.io.InputStream</classname> /
|
|
<classname>java.io.Reader</classname> for access to the
|
|
request's content. This value is the raw InputStream/Reader as
|
|
exposed by the Servlet API.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>java.io.OutputStream</classname> /
|
|
<classname>java.io.Writer</classname> for generating the
|
|
response's content. This value is the raw OutputStream/Writer as
|
|
exposed by the Servlet API.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>java.security.Principal</interfacename>
|
|
containing the currently authenticated user.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>@PathVariable</classname> annotated parameters
|
|
for access to URI template variables. See <xref
|
|
linkend="mvc-ann-requestmapping-uri-templates" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>@RequestParam</classname> annotated parameters
|
|
for access to specific Servlet request parameters. Parameter
|
|
values are converted to the declared method argument type. See
|
|
<xref linkend="mvc-ann-requestparam" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>@RequestHeader</interfacename> annotated
|
|
parameters for access to specific Servlet request HTTP headers.
|
|
Parameter values are converted to the declared method argument
|
|
type.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>@RequestBody</interfacename> annotated
|
|
parameters for access to the HTTP request body. Parameter values
|
|
are converted to the declared method argument type using
|
|
<interfacename>HttpMessageConverter</interfacename>s. See <xref
|
|
linkend="mvc-ann-requestbody" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>@RequestPart</interfacename> annotated
|
|
parameters for access to the content of a "multipart/form-data"
|
|
request part. See <xref
|
|
linkend="mvc-multipart-forms-non-browsers" /> and <xref
|
|
linkend="mvc-multipart" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>HttpEntity<?></classname> parameters for
|
|
access to the Servlet request HTTP headers and contents. The
|
|
request stream will be converted to the entity body using
|
|
<interfacename>HttpMessageConverter</interfacename>s. See <xref
|
|
linkend="mvc-ann-httpentity" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>java.util.Map</interfacename> /
|
|
<interfacename>org.springframework.ui.Model</interfacename> /
|
|
<classname>org.springframework.ui.ModelMap</classname> for
|
|
enriching the implicit model that is exposed to the web
|
|
view.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><interfacename>org.springframework.web.servlet.mvc.support.RedirectAttributes</interfacename>
|
|
to specify the exact set of attributes to use in case of a
|
|
redirect and also to add flash attributes (attributes stored
|
|
temporarily on the server-side to make them available to the
|
|
request after the redirect).
|
|
<literal>RedirectAttributes</literal> is used instead of the
|
|
implicit model if the method returns a "redirect:" prefixed view
|
|
name or <classname>RedirectView</classname>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Command or form objects to bind request parameters to bean
|
|
properties (via setters) or directly to fields, with
|
|
customizable type conversion, depending on
|
|
<classname>@InitBinder</classname> methods and/or the
|
|
HandlerAdapter configuration. See the
|
|
<literal>webBindingInitializer</literal> property on
|
|
<classname>RequestMappingHandlerAdapter</classname>. Such
|
|
command objects along with their validation results will be
|
|
exposed as model attributes by default, using the command class
|
|
class name - e.g. model attribute "orderAddress" for a command
|
|
object of type "some.package.OrderAddress". The
|
|
<classname>ModelAttribute</classname> annotation can be used on
|
|
a method argument to customize the model attribute name
|
|
used.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>org.springframework.validation.Errors</classname>
|
|
/
|
|
<classname>org.springframework.validation.BindingResult</classname>
|
|
validation results for a preceding command or form object (the
|
|
immediately preceding method argument).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>org.springframework.web.bind.support.SessionStatus</classname>
|
|
status handle for marking form processing as complete, which
|
|
triggers the cleanup of session attributes that have been
|
|
indicated by the <classname>@SessionAttributes</classname>
|
|
annotation at the handler type level.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>org.springframework.web.util.UriComponentsBuilder</classname>
|
|
a builder for preparing a URL relative to the current request's
|
|
host, port, scheme, context path, and the literal part of the
|
|
servlet mapping.</para>
|
|
</listitem>
|
|
</itemizedlist></para>
|
|
|
|
<para>The <interfacename>Errors</interfacename> or
|
|
<interfacename>BindingResult</interfacename> parameters have to follow
|
|
the model object that is being bound immediately as the method
|
|
signature might have more that one model object and Spring will create
|
|
a separate <interfacename>BindingResult</interfacename> instance for
|
|
each of them so the following sample won't work:</para>
|
|
|
|
<example>
|
|
<title>Invalid ordering of BindingResult and @ModelAttribute</title>
|
|
|
|
<programlisting language="java">@RequestMapping(method = RequestMethod.POST)
|
|
public String processSubmit(<emphasis role="bold">@ModelAttribute("pet") Pet pet</emphasis>,
|
|
Model model, <emphasis role="bold">BindingResult result</emphasis>) { … }</programlisting>
|
|
|
|
<para>Note, that there is a <interfacename>Model</interfacename>
|
|
parameter in between <classname>Pet</classname> and
|
|
<interfacename>BindingResult</interfacename>. To get this working
|
|
you have to reorder the parameters as follows:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(method = RequestMethod.POST)
|
|
public String processSubmit(<emphasis role="bold">@ModelAttribute("pet") Pet pet</emphasis>,
|
|
<emphasis role="bold">BindingResult result</emphasis>, Model model) { … }</programlisting>
|
|
</example>
|
|
</section>
|
|
|
|
<section id="mvc-ann-return-types">
|
|
<title>Supported method return types</title>
|
|
|
|
<para>The following are the supported return types: <itemizedlist>
|
|
<listitem>
|
|
<para>A <classname>ModelAndView</classname> object, with the
|
|
model implicitly enriched with command objects and the results
|
|
of <literal>@ModelAttribute</literal> annotated reference data
|
|
accessor methods.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <interfacename>Model</interfacename> object, with the
|
|
view name implicitly determined through a
|
|
<interfacename>RequestToViewNameTranslator</interfacename> and
|
|
the model implicitly enriched with command objects and the
|
|
results of <literal>@ModelAttribute</literal> annotated
|
|
reference data accessor methods.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <interfacename>Map</interfacename> object for exposing a
|
|
model, with the view name implicitly determined through a
|
|
<interfacename>RequestToViewNameTranslator</interfacename> and
|
|
the model implicitly enriched with command objects and the
|
|
results of <literal>@ModelAttribute</literal> annotated
|
|
reference data accessor methods.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <interfacename>View</interfacename> object, with the
|
|
model implicitly determined through command objects and
|
|
<literal>@ModelAttribute</literal> annotated reference data
|
|
accessor methods. The handler method may also programmatically
|
|
enrich the model by declaring a
|
|
<interfacename>Model</interfacename> argument (see above).<!--see above where? Need more explicit reference. same problem with next item.--></para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>String</classname> value that is interpreted
|
|
as the logical view name, with the model implicitly determined
|
|
through command objects and <literal>@ModelAttribute</literal>
|
|
annotated reference data accessor methods. The handler method
|
|
may also programmatically enrich the model by declaring a
|
|
<interfacename>Model</interfacename> argument (see
|
|
above).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><literal>void</literal> if the method handles the response
|
|
itself (by writing the response content directly, declaring an
|
|
argument of type <interfacename>ServletResponse</interfacename>
|
|
/ <interfacename>HttpServletResponse</interfacename> for that
|
|
purpose) or if the view name is supposed to be implicitly
|
|
determined through a
|
|
<interfacename>RequestToViewNameTranslator</interfacename> (not
|
|
declaring a response argument in the handler method
|
|
signature).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If the method is annotated with
|
|
<interfacename>@ResponseBody</interfacename>, the return type is
|
|
written to the response HTTP body. The return value will be
|
|
converted to the declared method argument type using
|
|
<interfacename>HttpMessageConverter</interfacename>s. See <xref
|
|
linkend="mvc-ann-responsebody" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>HttpEntity<?></classname> or
|
|
<classname>ResponseEntity<?></classname> object to provide
|
|
access to the Servlet response HTTP headers and contents. The
|
|
entity body will be converted to the response stream using
|
|
<interfacename>HttpMessageConverter</interfacename>s. See <xref
|
|
linkend="mvc-ann-httpentity" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Any other return type is considered to be a single model
|
|
attribute to be exposed to the view, using the attribute name
|
|
specified through <literal>@ModelAttribute</literal> at the
|
|
method level (or the default attribute name based on the return
|
|
type class name). The model is implicitly enriched with command
|
|
objects and the results of <literal>@ModelAttribute</literal>
|
|
annotated reference data accessor methods.</para>
|
|
</listitem>
|
|
</itemizedlist></para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestparam">
|
|
<title>Binding request parameters to method parameters with
|
|
<interfacename>@RequestParam</interfacename></title>
|
|
|
|
<para>Use the <classname>@RequestParam</classname> annotation to bind
|
|
request parameters to a method parameter in your controller.</para>
|
|
|
|
<para>The following code snippet shows the usage:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping("/pets")
|
|
@SessionAttributes("pet")
|
|
public class EditPetForm {
|
|
|
|
<lineannotation>// ...</lineannotation>
|
|
|
|
@RequestMapping(method = RequestMethod.GET)
|
|
public String setupForm(<emphasis role="bold">@RequestParam("petId") int petId</emphasis>, ModelMap model) {
|
|
Pet pet = this.clinic.loadPet(petId);
|
|
model.addAttribute("pet", pet);
|
|
return "petForm";
|
|
}
|
|
|
|
<lineannotation>// ...</lineannotation></programlisting>
|
|
|
|
<para>Parameters using this annotation are required by default, but
|
|
you can specify that a parameter is optional by setting
|
|
<interfacename>@RequestParam</interfacename>'s
|
|
<literal>required</literal> attribute to <literal>false</literal>
|
|
(e.g., <literal>@RequestParam(value="id",
|
|
required=false)</literal>).</para>
|
|
|
|
<para>Type conversion is applied automatically if the target method
|
|
parameter type is not <classname>String</classname>. See <xref
|
|
linkend="mvc-ann-typeconversion" />.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestbody">
|
|
<title>Mapping the request body with the @RequestBody
|
|
annotation</title>
|
|
|
|
<para>The <classname>@RequestBody</classname> method parameter
|
|
annotation indicates that a method parameter should be bound to the
|
|
value of the HTTP request body. For example:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value = "/something", method = RequestMethod.PUT)
|
|
public void handle(@RequestBody String body, Writer writer) throws IOException {
|
|
writer.write(body);
|
|
}</programlisting>
|
|
|
|
<para>You convert the request body to the method argument by using an
|
|
<interfacename>HttpMessageConverter</interfacename>.
|
|
<interfacename>HttpMessageConverter</interfacename> is responsible for
|
|
converting from the HTTP request message to an object and converting
|
|
from an object to the HTTP response body. The
|
|
<classname>RequestMappingHandlerAdapter</classname> supports the
|
|
<classname>@RequestBody</classname> annotation with the following
|
|
default <interfacename>HttpMessageConverters</interfacename>:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><classname>ByteArrayHttpMessageConverter</classname>
|
|
converts byte arrays.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>StringHttpMessageConverter</classname> converts
|
|
strings.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>FormHttpMessageConverter</classname> converts
|
|
form data to/from a MultiValueMap<String, String>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>SourceHttpMessageConverter</classname> converts
|
|
to/from a javax.xml.transform.Source.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>For more information on these converters, see <link
|
|
linkend="rest-message-conversion">Message Converters</link>. Also note
|
|
that if using the MVC namespace, a wider range of message converters
|
|
are registered by default. See <xref
|
|
linkend="mvc-annotation-driven" /> for more information.</para>
|
|
|
|
<para>If you intend to read and write XML, you will need to configure
|
|
the <classname>MarshallingHttpMessageConverter</classname> with a
|
|
specific <interfacename>Marshaller</interfacename> and an
|
|
<interfacename>Unmarshaller</interfacename> implementation from the
|
|
<classname>org.springframework.oxm</classname> package. For
|
|
example:</para>
|
|
|
|
<programlisting language="xml"><bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
|
|
<property name="messageConverters">
|
|
<util:list id="beanList">
|
|
<ref bean="stringHttpMessageConverter"/>
|
|
<ref bean="marshallingHttpMessageConverter"/>
|
|
</util:list>
|
|
</property
|
|
</bean>
|
|
|
|
<bean id="stringHttpMessageConverter"
|
|
class="org.springframework.http.converter.StringHttpMessageConverter"/>
|
|
|
|
<bean id="marshallingHttpMessageConverter"
|
|
class="org.springframework.http.converter.xml.MarshallingHttpMessageConverter">
|
|
<property name="marshaller" ref="castorMarshaller" />
|
|
<property name="unmarshaller" ref="castorMarshaller" />
|
|
</bean>
|
|
|
|
<bean id="castorMarshaller" class="org.springframework.oxm.castor.CastorMarshaller"/></programlisting>
|
|
|
|
<para>An <classname>@RequestBody</classname> method parameter can be
|
|
annotated with <classname>@Valid</classname>, in which case it will be
|
|
validated using the configured <classname>Validator</classname>
|
|
instance. When using the MVC namespace a JSR-303 validator is
|
|
configured automatically assuming a JSR-303 implementation is
|
|
available on the classpath.</para>
|
|
<para>Unlike <classname>@ModelAttribute</classname> parameters, for which
|
|
a <classname>BindingResult</classname> can be used to examine the errors,
|
|
<classname>@RequestBody</classname> validation errors always result in a
|
|
<classname>MethodArgumentNotValidException</classname> being raised.
|
|
The exception is handled in the
|
|
<classname>DefaultHandlerExceptionResolver</classname>, which sends
|
|
a <literal>400</literal> error back to the client.</para>
|
|
|
|
<note>
|
|
<para>Also see <xref linkend="mvc-annotation-driven" /> for
|
|
information on configuring message converters and a validator
|
|
through the MVC namespace.</para>
|
|
</note>
|
|
</section>
|
|
|
|
<section id="mvc-ann-responsebody">
|
|
<title>Mapping the response body with the
|
|
<interfacename>@ResponseBody</interfacename> annotation</title>
|
|
|
|
<para>The <interfacename>@ResponseBody</interfacename> annotation is
|
|
similar to <interfacename>@RequestBody</interfacename>. This
|
|
annotation can be put on a method and indicates that the return type
|
|
should be written straight to the HTTP response body (and not placed
|
|
in a Model, or interpreted as a view name). For example:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value = "/something", method = RequestMethod.PUT)
|
|
@ResponseBody
|
|
public String helloWorld() {
|
|
return "Hello World";
|
|
}</programlisting>
|
|
|
|
<para>The above example will result in the text <literal>Hello
|
|
World</literal> being written to the HTTP response stream.</para>
|
|
|
|
<para>As with <interfacename>@RequestBody</interfacename>, Spring
|
|
converts the returned object to a response body by using an
|
|
<interfacename>HttpMessageConverter</interfacename>. For more
|
|
information on these converters, see the previous section and <link
|
|
linkend="rest-message-conversion">Message Converters</link>.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-httpentity">
|
|
<title>Using <classname>HttpEntity<?></classname></title>
|
|
|
|
<para>The <classname>HttpEntity</classname> is similar to
|
|
<interfacename>@RequestBody</interfacename> and
|
|
<interfacename>@ResponseBody</interfacename>. Besides getting access
|
|
to the request and response body, <classname>HttpEntity</classname>
|
|
(and the response-specific subclass
|
|
<classname>ResponseEntity</classname>) also allows access to the
|
|
request and response headers, like so:</para>
|
|
|
|
<programlisting language="java">@RequestMapping("/something")
|
|
public ResponseEntity<String> handle(HttpEntity<byte[]> requestEntity) throws UnsupportedEncodingException {
|
|
String requestHeader = requestEntity.getHeaders().getFirst("MyRequestHeader"));
|
|
byte[] requestBody = requestEntity.getBody();
|
|
// do something with request header and body
|
|
|
|
HttpHeaders responseHeaders = new HttpHeaders();
|
|
responseHeaders.set("MyResponseHeader", "MyValue");
|
|
return new ResponseEntity<String>("Hello World", responseHeaders, HttpStatus.CREATED);
|
|
}</programlisting>
|
|
|
|
<para>The above example gets the value of the
|
|
<literal>MyRequestHeader</literal> request header, and reads the body
|
|
as a byte array. It adds the <literal>MyResponseHeader</literal> to
|
|
the response, writes <literal>Hello World</literal> to the response
|
|
stream, and sets the response status code to 201 (Created).</para>
|
|
|
|
<para>As with <interfacename>@RequestBody</interfacename> and
|
|
<interfacename>@ResponseBody</interfacename>, Spring uses
|
|
<interfacename>HttpMessageConverter</interfacename> to convert from
|
|
and to the request and response streams. For more information on these
|
|
converters, see the previous section and <link
|
|
linkend="rest-message-conversion">Message Converters</link>.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-modelattrib-methods">
|
|
<title>Using <interfacename>@ModelAttribute</interfacename> on a
|
|
method</title>
|
|
|
|
<para>The <interfacename>@ModelAttribute</interfacename> annotation
|
|
can be used on methods or on method arguments. This section explains
|
|
its usage on methods while the next section explains its usage on
|
|
method arguments.</para>
|
|
|
|
<para>An <interfacename>@ModelAttribute</interfacename> on a method
|
|
indicates the purpose of that method is to add one or more model
|
|
attributes. Such methods support the same argument types as
|
|
<interfacename>@RequestMapping</interfacename> methods but cannot be
|
|
mapped directly to requests. Instead
|
|
<interfacename>@ModelAttribute</interfacename> methods in a controller
|
|
are invoked before <interfacename>@RequestMapping</interfacename>
|
|
methods, within the same controller. A couple of examples:</para>
|
|
|
|
<programlisting language="java">
|
|
// Add one attribute
|
|
// The return value of the method is added to the model under the name "account"
|
|
// You can customize the name via @ModelAttribute("myAccount")
|
|
|
|
@ModelAttribute
|
|
public Account addAccount(@RequestParam String number) {
|
|
return accountManager.findAccount(number);
|
|
}
|
|
|
|
// Add multiple attributes
|
|
|
|
@ModelAttribute
|
|
public void populateModel(@RequestParam String number, Model model) {
|
|
model.addAttribute(accountManager.findAccount(number));
|
|
// add more ...
|
|
}</programlisting>
|
|
|
|
<para><interfacename>@ModelAttribute</interfacename> methods are used
|
|
to populate the model with commonly needed attributes for example to
|
|
fill a drop-down with states or with pet types, or to retrieve a
|
|
command object like Account in order to use it to represent the data
|
|
on an HTML form. The latter case is further discussed in the next
|
|
section.</para>
|
|
|
|
<para>Note the two styles of
|
|
<interfacename>@ModelAttribute</interfacename> methods. In the first,
|
|
the method adds an attribute implicitly by returning it. In the
|
|
second, the method accepts a <classname>Model</classname> and adds any
|
|
number of model attributes to it. You can choose between the two
|
|
styles depending on your needs.</para>
|
|
|
|
<para>A controller can have any number of
|
|
<interfacename>@ModelAttribute</interfacename> methods. All such
|
|
methods are invoked before
|
|
<interfacename>@RequestMapping</interfacename> methods of the same
|
|
controller.</para>
|
|
|
|
<tip>
|
|
<para>What happens when a model attribute name is not explicitly
|
|
specified? In such cases a default name is assigned to the model
|
|
attribute based on its type. For example if the method returns an
|
|
object of type <classname>Account</classname>, the default name used
|
|
is "account". You can change that through the value of the
|
|
<interfacename>@ModelAttribute</interfacename> annotation. If adding
|
|
attributes directly to the <classname>Model</classname>, use the
|
|
appropriate overloaded <literal>addAttribute(..)</literal> method -
|
|
i.e., with or without an attribute name.</para>
|
|
</tip>
|
|
|
|
<para>The <interfacename>@ModelAttribute</interfacename> annotation
|
|
can be used on <interfacename>@RequestMapping</interfacename> methods
|
|
as well. In that case the return value of the
|
|
<interfacename>@RequestMapping</interfacename> method is interpreted
|
|
as a model attribute rather than as a view name. The view name is
|
|
derived from view name conventions instead much like for methods
|
|
returning void — see <xref linkend="mvc-coc-r2vnt" />.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-modelattrib-method-args">
|
|
<title>Using <interfacename>@ModelAttribute</interfacename> on a
|
|
method argument</title>
|
|
|
|
<para>As explained in the previous section
|
|
<interfacename>@ModelAttribute</interfacename> can be used on methods
|
|
or on method arguments. This section explains its usage on method
|
|
arguments.</para>
|
|
|
|
<para>An <interfacename>@ModelAttribute</interfacename> on a method
|
|
argument indicates the argument should be retrieved from the model. If
|
|
not present in the model, the argument should be instantiated first
|
|
and then added to the model. Once present in the model, the argument's
|
|
fields should be populated from all request parameters that have
|
|
matching names. This is known as data binding in Spring MVC, a very
|
|
useful mechanism that saves you from having to parse each form field
|
|
individually.</para>
|
|
|
|
<programlisting language="java">
|
|
@RequestMapping(value="/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST)
|
|
public String processSubmit(<emphasis role="bold">@ModelAttribute Pet pet</emphasis>) {
|
|
|
|
}</programlisting>
|
|
|
|
<para>Given the above example where can the Pet instance come from?
|
|
There are several options:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>It may already be in the model due to use of
|
|
<interfacename>@SessionAttributes</interfacename> — see <xref
|
|
linkend="mvc-ann-sessionattrib" />.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>It may already be in the model due to an
|
|
<interfacename>@ModelAttribute</interfacename> method in the same
|
|
controller — as explained in the previous section.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>It may be retrieved based on a URI template variable and
|
|
type converter (explained in more detail below).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>It may be instantiated using its default constructor.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>An <interfacename>@ModelAttribute</interfacename> method is a
|
|
common way to to retrieve an attribute from the database, which may
|
|
optionally be stored between requests through the use of
|
|
<interfacename>@SessionAttributes</interfacename>. In some cases it
|
|
may be convenient to retrieve the attribute by using an URI template
|
|
variable and a type converter. Here is an example:</para>
|
|
|
|
<programlisting language="java">
|
|
@RequestMapping(value="/accounts/{account}", method = RequestMethod.PUT)
|
|
public String save(@ModelAttribute("account") Account account) {
|
|
|
|
}</programlisting>
|
|
|
|
<para>In this example the name of the model attribute (i.e. "account")
|
|
matches the name of a URI template variable. If you register
|
|
<classname>Converter<String, Account></classname> that can turn
|
|
the <literal>String</literal> account value into an
|
|
<classname>Account</classname> instance, then the above example will
|
|
work without the need for an
|
|
<interfacename>@ModelAttribute</interfacename> method.</para>
|
|
|
|
<para>The next step is data binding. The
|
|
<classname>WebDataBinder</classname> class matches request parameter
|
|
names — including query string parameters and form fields — to model
|
|
attribute fields by name. Matching fields are populated after type
|
|
conversion (from String to the target field type) has been applied
|
|
where necessary. Data binding and validation are covered in <xref
|
|
linkend="validation" />. Customizing the data binding process for a
|
|
controller level is covered in <xref
|
|
linkend="mvc-ann-webdatabinder" />.</para>
|
|
|
|
<para>As a result of data binding there may be errors such as missing
|
|
required fields or type conversion errors. To check for such errors
|
|
add a <classname>BindingResult</classname> argument immediately
|
|
following the <interfacename>@ModelAttribute</interfacename>
|
|
argument:</para>
|
|
|
|
<programlisting language="java">
|
|
@RequestMapping(value="/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST)
|
|
public String processSubmit(<emphasis role="bold">@ModelAttribute("pet") Pet pet</emphasis>, BindingResult result) {
|
|
|
|
if (result.hasErrors()) {
|
|
return "petForm";
|
|
}
|
|
|
|
// ...
|
|
|
|
}</programlisting>
|
|
|
|
<para>With a <classname>BindingResult</classname> you can check if
|
|
errors were found in which case it's common to render the same form
|
|
where the errors can be shown with the help of Spring's
|
|
<literal><errors></literal> form tag.</para>
|
|
|
|
<para>In addition to data binding you can also invoke validation using
|
|
your own custom validator passing the same
|
|
<classname>BindingResult</classname> that was used to record data
|
|
binding errors. That allows for data binding and validation errors to
|
|
be accumulated in one place and subsequently reported back to the
|
|
user:</para>
|
|
|
|
<programlisting language="java">
|
|
@RequestMapping(value="/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST)
|
|
public String processSubmit(<emphasis role="bold">@ModelAttribute("pet") Pet pet</emphasis>, BindingResult result) {
|
|
|
|
new PetValidator().validate(pet, result);
|
|
if (result.hasErrors()) {
|
|
return "petForm";
|
|
}
|
|
|
|
// ...
|
|
}</programlisting>
|
|
|
|
<para>Or you can have validation invoked automatically by adding the
|
|
JSR-303 <interfacename>@Valid</interfacename> annotation:</para>
|
|
|
|
<programlisting language="java">
|
|
@RequestMapping(value="/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST)
|
|
public String processSubmit(<emphasis role="bold">@Valid @ModelAttribute("pet") Pet pet</emphasis>, BindingResult result) {
|
|
|
|
if (result.hasErrors()) {
|
|
return "petForm";
|
|
}
|
|
|
|
// ...
|
|
}</programlisting>
|
|
|
|
<para>See <xref linkend="validation-beanvalidation" /> and <xref
|
|
linkend="validation" /> for details on how to configure and use
|
|
validation.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-sessionattrib">
|
|
<title>Using <classname>@SessionAttributes</classname> to store model
|
|
attributes in the HTTP session between requests</title>
|
|
|
|
<para>The type-level <classname>@SessionAttributes</classname>
|
|
annotation declares session attributes used by a specific handler.
|
|
This will typically list the names of model attributes or types of
|
|
model attributes which should be transparently stored in the session
|
|
or some conversational storage, serving as form-backing beans between
|
|
subsequent requests.</para>
|
|
|
|
<para>The following code snippet shows the usage of this annotation,
|
|
specifying the model attribute name:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
@RequestMapping("/editPet.do")
|
|
<emphasis role="bold">@SessionAttributes("pet")</emphasis>
|
|
public class EditPetForm {
|
|
<lineannotation>// ...</lineannotation>
|
|
}</programlisting>
|
|
|
|
<note>
|
|
<para>When using controller interfaces (e.g., for AOP proxying),
|
|
make sure to consistently put <emphasis>all</emphasis> your mapping
|
|
annotations - such as <interfacename>@RequestMapping</interfacename>
|
|
and <interfacename>@SessionAttributes</interfacename> - on the
|
|
controller <emphasis>interface</emphasis> rather than on the
|
|
implementation class.</para>
|
|
</note>
|
|
</section>
|
|
|
|
<section id="mvc-ann-redirect-attributes">
|
|
<title>Specifying redirect and flash attributes</title>
|
|
|
|
<para>By default all model attributes are considered to be exposed as
|
|
URI template variables in the redirect URL. Of the remaining
|
|
attributes those that are primitive types or collections/arrays of
|
|
primitive types are automatically appended as query parameters.</para>
|
|
|
|
<para>In annotated controllers however the model may contain
|
|
additional attributes originally added for rendering purposes (e.g.
|
|
drop-down field values). To gain precise control over the attributes
|
|
used in a redirect scenario, an
|
|
<interfacename>@RequestMapping</interfacename> method can declare an
|
|
argument of type <interfacename>RedirectAttributes</interfacename> and
|
|
use it to add attributes for use in
|
|
<classname>RedirectView</classname>. If the controller method does
|
|
redirect, the content of
|
|
<interfacename>RedirectAttributes</interfacename> is used. Otherwise
|
|
the content of the default <interfacename>Model</interfacename> is
|
|
used.</para>
|
|
|
|
<para>The <classname>RequestMappingHandlerAdapter</classname> provides
|
|
a flag called <literal>"ignoreDefaultModelOnRedirect"</literal> that
|
|
can be used to indicate the content of the default
|
|
<interfacename>Model</interfacename> should never be used if a
|
|
controller method redirects. Instead the controller method should
|
|
declare an attribute of type
|
|
<interfacename>RedirectAttributes</interfacename> or if it doesn't do
|
|
so no attributes should be passed on to
|
|
<classname>RedirectView</classname>. Both the MVC namespace and the
|
|
MVC Java config (via <interfacename>@EnableWebMvc</interfacename>)
|
|
keep this flag set to <literal>false</literal> in order to maintain
|
|
backwards compatibility. However, for new applications we recommend
|
|
setting it to <literal>true</literal></para>
|
|
|
|
<para>The <interfacename>RedirectAttributes</interfacename> interface
|
|
can also be used to add flash attributes. Unlike other redirect
|
|
attributes, which end up in the target redirect URL, flash attributes
|
|
are saved in the HTTP session (and hence do not appear in the URL).
|
|
The model of the controller serving the target redirect URL
|
|
automatically receives these flash attributes after which they are
|
|
removed from the session. See <xref linkend="mvc-flash-attributes" />
|
|
for an overview of the general support for flash attributes in Spring
|
|
MVC.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-form-urlencoded-data">
|
|
<title>Working with
|
|
<literal>"application/x-www-form-urlencoded"</literal> data</title>
|
|
|
|
<para>The previous sections covered use of
|
|
<interfacename>@ModelAttribute</interfacename> to support form
|
|
submission requests from browser clients. The same annotation is
|
|
recommended for use with requests from non-browser clients as well.
|
|
However there is one notable difference when it comes to working with
|
|
HTTP PUT requests. Browsers can submit form data via HTTP GET or HTTP
|
|
POST. Non-browser clients can also submit forms via HTTP PUT. This
|
|
presents a challenge because the Servlet specification requires the
|
|
<literal>ServletRequest.getParameter*()</literal> family of methods to
|
|
support form field access only for HTTP POST, not for HTTP PUT.</para>
|
|
|
|
<para>To support HTTP PUT and PATCH requests, the <literal>spring-web</literal>
|
|
module provides the filter
|
|
<classname>HttpPutFormContentFilter</classname>, which can be
|
|
configured in <filename>web.xml</filename>:</para>
|
|
|
|
<programlisting language="xml"><filter>
|
|
<filter-name>httpPutFormFilter</filter-name>
|
|
<filter-class>org.springframework.web.filter.HttpPutFormContentFilter</filter-class>
|
|
</filter>
|
|
|
|
<filter-mapping>
|
|
<filter-name>httpPutFormFilter</filter-name>
|
|
<servlet-name>dispatcherServlet</servlet-name>
|
|
</filter-mapping>
|
|
|
|
<servlet>
|
|
<servlet-name>dispatcherServlet</servlet-name>
|
|
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
|
|
</servlet></programlisting>
|
|
|
|
<para>The above filter intercepts HTTP PUT and PATCH requests with content type
|
|
<literal>application/x-www-form-urlencoded</literal>, reads the form
|
|
data from the body of the request, and wraps the
|
|
<classname>ServletRequest</classname> in order to make the form data
|
|
available through the
|
|
<literal>ServletRequest.getParameter*()</literal> family of
|
|
methods.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-cookievalue">
|
|
<title>Mapping cookie values with the @CookieValue annotation</title>
|
|
|
|
<para>The <interfacename>@CookieValue</interfacename> annotation
|
|
allows a method parameter to be bound to the value of an HTTP
|
|
cookie.</para>
|
|
|
|
<para>Let us consider that the following cookie has been received with
|
|
an http request:</para>
|
|
|
|
<programlisting>JSESSIONID=415A4AC178C59DACE0B2C9CA727CDD84</programlisting>
|
|
|
|
<para>The following code sample demonstrates how to get the value of
|
|
the <literal>JSESSIONID</literal> cookie:</para>
|
|
|
|
<programlisting language="java">@RequestMapping("/displayHeaderInfo.do")
|
|
public void displayHeaderInfo(<emphasis role="bold">@CookieValue("JSESSIONID")</emphasis> String cookie) {
|
|
|
|
//...
|
|
|
|
}</programlisting>
|
|
|
|
<para>Type conversion is applied automatically if the target method
|
|
parameter type is not <classname>String</classname>. See <xref
|
|
linkend="mvc-ann-typeconversion" />.</para>
|
|
|
|
<para>This annotation is supported for annotated handler methods in
|
|
Servlet and Portlet environments.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-requestheader">
|
|
<title>Mapping request header attributes with the @RequestHeader
|
|
annotation</title>
|
|
|
|
<para>The <interfacename>@RequestHeader</interfacename> annotation
|
|
allows a method parameter to be bound to a request header.</para>
|
|
|
|
<para>Here is a sample request header:</para>
|
|
|
|
<programlisting>
|
|
Host localhost:8080
|
|
Accept text/html,application/xhtml+xml,application/xml;q=0.9
|
|
Accept-Language fr,en-gb;q=0.7,en;q=0.3
|
|
Accept-Encoding gzip,deflate
|
|
Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7
|
|
Keep-Alive 300</programlisting>
|
|
|
|
<para>The following code sample demonstrates how to get the value of
|
|
the <literal>Accept-Encoding</literal> and
|
|
<literal>Keep-Alive</literal> headers:</para>
|
|
|
|
<programlisting language="java">@RequestMapping("/displayHeaderInfo.do")
|
|
public void displayHeaderInfo(<emphasis role="bold">@RequestHeader("Accept-Encoding")</emphasis> String encoding,
|
|
<emphasis role="bold">@RequestHeader("Keep-Alive")</emphasis> long keepAlive) {
|
|
|
|
//...
|
|
|
|
}</programlisting>
|
|
|
|
<para>Type conversion is applied automatically if the method parameter
|
|
is not <classname>String</classname>. See <xref
|
|
linkend="mvc-ann-typeconversion" />.</para>
|
|
|
|
<tip>
|
|
<para>Built-in support is available for converting a comma-separated
|
|
string into an array/collection of strings or other types known to
|
|
the type conversion system. For example a method parameter annotated
|
|
with <literal>@RequestHeader("Accept")</literal> may be of type
|
|
<classname>String</classname> but also
|
|
<classname>String[]</classname> or
|
|
<classname>List<String></classname>.</para>
|
|
</tip>
|
|
|
|
<para>This annotation is supported for annotated handler methods in
|
|
Servlet and Portlet environments.</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-typeconversion">
|
|
<title>Method Parameters And Type Conversion</title>
|
|
|
|
<para>String-based values extracted from the request including request
|
|
parameters, path variables, request headers, and cookie values may
|
|
need to be converted to the target type of the method parameter or
|
|
field (e.g., binding a request parameter to a field in an
|
|
<interfacename>@ModelAttribute</interfacename> parameter) they're
|
|
bound to. If the target type is not <classname>String</classname>,
|
|
Spring automatically converts to the appropriate type. All simple
|
|
types such as int, long, Date, etc. are supported. You can further
|
|
customize the conversion process through a
|
|
<classname>WebDataBinder</classname> (see <xref
|
|
linkend="mvc-ann-webdatabinder" />) or by registering
|
|
<classname>Formatters</classname> with the
|
|
<classname>FormattingConversionService</classname> (see <xref
|
|
linkend="format" />).</para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-webdatabinder">
|
|
<title>Customizing <classname>WebDataBinder</classname>
|
|
initialization</title>
|
|
|
|
<para>To customize request parameter binding with PropertyEditors
|
|
through Spring's <classname>WebDataBinder</classname>, you can use
|
|
either <interfacename>@InitBinder</interfacename>-annotated methods
|
|
within your controller or externalize your configuration by providing
|
|
a custom <interfacename>WebBindingInitializer</interfacename>.</para>
|
|
|
|
<section id="mvc-ann-initbinder">
|
|
<title>Customizing data binding with
|
|
<interfacename>@InitBinder</interfacename></title>
|
|
|
|
<para>Annotating controller methods with
|
|
<interfacename>@InitBinder</interfacename> allows you to configure
|
|
web data binding directly within your controller class.
|
|
<interfacename>@InitBinder</interfacename> identifies methods that
|
|
initialize the <classname>WebDataBinder</classname> that will be
|
|
used to populate command and form object arguments of annotated
|
|
handler methods.</para>
|
|
|
|
<para>Such init-binder methods support all arguments that
|
|
<interfacename>@RequestMapping</interfacename> supports, except for
|
|
command/form objects and corresponding validation result objects.
|
|
Init-binder methods must not have a return value. Thus, they are
|
|
usually declared as <literal>void</literal>. Typical arguments
|
|
include <classname>WebDataBinder</classname> in combination with
|
|
<interfacename>WebRequest</interfacename> or
|
|
<classname>java.util.Locale</classname>, allowing code to register
|
|
context-specific editors.</para>
|
|
|
|
<para>The following example demonstrates the use of
|
|
<interfacename>@InitBinder</interfacename> to configure a
|
|
<classname>CustomDateEditor</classname> for all
|
|
<classname>java.util.Date</classname> form properties.</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class MyFormController {
|
|
|
|
<emphasis role="bold">@InitBinder</emphasis>
|
|
public void initBinder(WebDataBinder binder) {
|
|
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
|
|
dateFormat.setLenient(false);
|
|
binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, false));
|
|
}
|
|
|
|
<lineannotation>// ...</lineannotation>
|
|
}</programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-ann-webbindinginitializer">
|
|
<title>Configuring a custom
|
|
<interfacename>WebBindingInitializer</interfacename></title>
|
|
|
|
<para>To externalize data binding initialization, you can provide a
|
|
custom implementation of the
|
|
<interfacename>WebBindingInitializer</interfacename> interface,
|
|
which you then enable by supplying a custom bean configuration for
|
|
an <classname>AnnotationMethodHandlerAdapter</classname>, thus
|
|
overriding the default configuration.</para>
|
|
|
|
<para>The following example from the PetClinic application shows a
|
|
configuration using a custom implementation of the
|
|
<interfacename>WebBindingInitializer</interfacename> interface,
|
|
<classname>org.springframework.samples.petclinic.web.ClinicBindingInitializer</classname>,
|
|
which configures PropertyEditors required by several of the
|
|
PetClinic controllers.</para>
|
|
|
|
<programlisting language="xml"><bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
|
|
<property name="cacheSeconds" value="0" />
|
|
<property name="webBindingInitializer">
|
|
<bean class="org.springframework.samples.petclinic.web.ClinicBindingInitializer" />
|
|
</property>
|
|
</bean></programlisting>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-ann-lastmodified">
|
|
<title>Support for the 'Last-Modified' Response Header To Facilitate
|
|
Content Caching</title>
|
|
|
|
<para>An <interfacename>@RequestMapping</interfacename> method may
|
|
wish to support <literal>'Last-Modified'</literal> HTTP requests, as
|
|
defined in the contract for the Servlet API's
|
|
<literal>getLastModified</literal> method, to facilitate content
|
|
caching. This involves calculating a lastModified
|
|
<literal>long</literal> value for a given request, comparing it
|
|
against the <literal>'If-Modified-Since'</literal> request header
|
|
value, and potentially returning a response with status code 304 (Not
|
|
Modified). An annotated controller method can achieve that as
|
|
follows:</para>
|
|
|
|
<programlisting language="java">
|
|
@RequestMapping
|
|
public String myHandleMethod(WebRequest webRequest, Model model) {
|
|
|
|
long lastModified = // 1. application-specific calculation
|
|
|
|
if (request.checkNotModified(lastModified)) {
|
|
// 2. shortcut exit - no further processing necessary
|
|
return null;
|
|
}
|
|
|
|
// 3. or otherwise further request processing, actually preparing content
|
|
model.addAttribute(...);
|
|
return "myViewName";
|
|
}</programlisting>
|
|
|
|
<para>There are two key elements to note: calling
|
|
<code>request.checkNotModified(lastModified)</code> and returning
|
|
<literal>null</literal>. The former sets the response status to 304
|
|
before it returns <literal>true</literal>. The latter, in combination
|
|
with the former, causes Spring MVC to do no further processing of the
|
|
request.</para>
|
|
</section>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-handlermapping">
|
|
<title>Handler mappings</title>
|
|
|
|
<para>In previous versions of Spring, users were required to define one or
|
|
more <interfacename>HandlerMapping</interfacename> beans in the web
|
|
application context to map incoming web requests to appropriate handlers.
|
|
With the introduction of annotated controllers, you generally don't need
|
|
to do that because the <classname>RequestMappingHandlerMapping</classname>
|
|
automatically looks for <interfacename>@RequestMapping</interfacename>
|
|
annotations on all <interfacename>@Controller</interfacename> beans.
|
|
However, do keep in mind that all <classname>HandlerMapping</classname>
|
|
classes extending from <classname>AbstractHandlerMapping</classname> have
|
|
the following properties that you can use to customize their
|
|
behavior:</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term><literal>interceptors</literal></term>
|
|
|
|
<listitem>
|
|
<para>List of interceptors to use.
|
|
<interfacename>HandlerInterceptor</interfacename>s are discussed in
|
|
<xref linkend="mvc-handlermapping-interceptor" />.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>defaultHandler</literal></term>
|
|
|
|
<listitem>
|
|
<para>Default handler to use, when this handler mapping does not
|
|
result in a matching handler.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>order</literal></term>
|
|
|
|
<listitem>
|
|
<para>Based on the value of the order property (see the
|
|
<literal>org.springframework.core.Ordered</literal> interface),
|
|
Spring sorts all handler mappings available in the context and
|
|
applies the first matching handler.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>alwaysUseFullPath</literal></term>
|
|
|
|
<listitem>
|
|
<para>If <literal>true</literal> , Spring uses the full path within
|
|
the current Servlet context to find an appropriate handler. If
|
|
<literal>false</literal> (the default), the path within the current
|
|
Servlet mapping is used. For example, if a Servlet is mapped using
|
|
<literal>/testing/*</literal> and the
|
|
<literal>alwaysUseFullPath</literal> property is set to true,
|
|
<literal>/testing/viewPage.html</literal> is used, whereas if the
|
|
property is set to false, <literal>/viewPage.html</literal> is
|
|
used.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term><literal>urlDecode</literal></term>
|
|
|
|
<listitem>
|
|
<para>Defaults to <literal>true</literal>, as of Spring 2.5. If you
|
|
prefer to compare encoded paths, set this flag to
|
|
<literal>false</literal>. However, the
|
|
<interfacename>HttpServletRequest</interfacename> always exposes the
|
|
Servlet path in decoded form. Be aware that the Servlet path will
|
|
not match when compared with encoded paths.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>The following example shows how to configure an interceptor:</para>
|
|
|
|
<programlisting language="xml"><beans>
|
|
<bean id="handlerMapping" class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping">
|
|
<property name="interceptors">
|
|
<bean class="example.MyInterceptor"/>
|
|
</property>
|
|
</bean>
|
|
|
|
<beans></programlisting>
|
|
|
|
<section id="mvc-handlermapping-interceptor">
|
|
<title>Intercepting requests with a
|
|
<interfacename>HandlerInterceptor</interfacename></title>
|
|
|
|
<para>Spring's handler mapping mechanism includes handler interceptors,
|
|
which are useful when you want to apply specific functionality to
|
|
certain requests, for example, checking for a principal.</para>
|
|
|
|
<para>Interceptors located in the handler mapping must implement
|
|
<interfacename>HandlerInterceptor</interfacename> from the
|
|
<literal>org.springframework.web.servlet</literal> package. This
|
|
interface defines three methods: <literal>preHandle(..)</literal> is
|
|
called <emphasis>before</emphasis> the actual handler is executed;
|
|
<literal>postHandle(..)</literal> is called <emphasis>after</emphasis>
|
|
the handler is executed; and <literal>afterCompletion(..)</literal> is
|
|
called <emphasis>after the complete request has finished</emphasis>.
|
|
These three methods should provide enough flexibility to do all kinds of
|
|
preprocessing and postprocessing.</para>
|
|
|
|
<para>The <literal>preHandle(..)</literal> method returns a boolean
|
|
value. You can use this method to break or continue the processing of
|
|
the execution chain. When this method returns <literal>true</literal>,
|
|
the handler execution chain will continue; when it returns false, the
|
|
<classname>DispatcherServlet</classname> assumes the interceptor itself
|
|
has taken care of requests (and, for example, rendered an appropriate
|
|
view) and does not continue executing the other interceptors and the
|
|
actual handler in the execution chain.</para>
|
|
|
|
<para>Interceptors can be configured using the
|
|
<literal>interceptors</literal> property, which is present on all
|
|
<classname>HandlerMapping</classname> classes extending from
|
|
<classname>AbstractHandlerMapping</classname>. This is shown in the
|
|
example below:</para>
|
|
|
|
<programlisting language="xml"><beans>
|
|
<bean id="handlerMapping"
|
|
class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping">
|
|
<property name="interceptors">
|
|
<list>
|
|
<ref bean="officeHoursInterceptor"/>
|
|
</list>
|
|
</property>
|
|
</bean>
|
|
|
|
<bean id="officeHoursInterceptor"
|
|
class="samples.TimeBasedAccessInterceptor">
|
|
<property name="openingTime" value="9"/>
|
|
<property name="closingTime" value="18"/>
|
|
</bean>
|
|
<beans></programlisting>
|
|
|
|
<programlisting language="java">package samples;
|
|
|
|
public class TimeBasedAccessInterceptor extends HandlerInterceptorAdapter {
|
|
|
|
private int openingTime;
|
|
private int closingTime;
|
|
|
|
public void setOpeningTime(int openingTime) {
|
|
this.openingTime = openingTime;
|
|
}
|
|
|
|
public void setClosingTime(int closingTime) {
|
|
this.closingTime = closingTime;
|
|
}
|
|
|
|
public boolean preHandle(
|
|
HttpServletRequest request,
|
|
HttpServletResponse response,
|
|
Object handler) throws Exception {
|
|
|
|
Calendar cal = Calendar.getInstance();
|
|
int hour = cal.get(HOUR_OF_DAY);
|
|
if (openingTime <= hour && hour < closingTime) {
|
|
return true;
|
|
} else {
|
|
response.sendRedirect("http://host.com/outsideOfficeHours.html");
|
|
return false;
|
|
}
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>Any request handled by this mapping is intercepted by the
|
|
<classname>TimeBasedAccessInterceptor</classname>. If the current time
|
|
is outside office hours, the user is redirected to a static HTML file
|
|
that says, for example, you can only access the website during office
|
|
hours.</para>
|
|
|
|
<note>
|
|
<para>When using the
|
|
<classname>RequestMappingHandlerMapping</classname> the actual handler
|
|
is an instance of <classname>HandlerMethod</classname> which
|
|
identifies the specific controller method that will be invoked.</para>
|
|
</note>
|
|
|
|
<para>As you can see, the Spring adapter class
|
|
<classname>HandlerInterceptorAdapter</classname> makes it easier to
|
|
extend the <interfacename>HandlerInterceptor</interfacename>
|
|
interface.</para>
|
|
|
|
<tip>
|
|
<para>In the example above, the configured interceptor will apply to
|
|
all requests handled with annotated controller methods. If you want to
|
|
narrow down the URL paths to which an interceptor applies, you can use
|
|
the MVC namespace to do that. See <xref
|
|
linkend="mvc-annotation-driven" />.</para>
|
|
</tip>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-viewresolver">
|
|
<title>Resolving views</title>
|
|
|
|
<para>All MVC frameworks for web applications provide a way to address
|
|
views. Spring provides view resolvers, which enable you to render models
|
|
in a browser without tying you to a specific view technology. Out of the
|
|
box, Spring enables you to use JSPs, Velocity templates and XSLT views,
|
|
for example. See <xref linkend="view" /> for a discussion of how to
|
|
integrate and use a number of disparate view technologies.</para>
|
|
|
|
<para>The two interfaces that are important to the way Spring handles
|
|
views are <interfacename>ViewResolver</interfacename> and
|
|
<interfacename>View</interfacename>. The
|
|
<interfacename>ViewResolver</interfacename> provides a mapping between
|
|
view names and actual views. The <interfacename>View</interfacename>
|
|
interface addresses the preparation of the request and hands the request
|
|
over to one of the view technologies.</para>
|
|
|
|
<section id="mvc-viewresolver-resolver">
|
|
<title>Resolving views with the
|
|
<interfacename>ViewResolver</interfacename> interface</title>
|
|
|
|
<para>As discussed in <xref linkend="mvc-controller" />, all handler
|
|
methods in the Spring Web MVC controllers must resolve to a logical view
|
|
name, either explicitly (e.g., by returning a <literal>String</literal>,
|
|
<literal>View</literal>, or <literal>ModelAndView</literal>) or
|
|
implicitly (i.e., based on conventions). Views in Spring are addressed
|
|
by a logical view name and are resolved by a view resolver. Spring comes
|
|
with quite a few view resolvers. This table lists most of them; a couple
|
|
of examples follow.</para>
|
|
|
|
<table id="mvc-view-resolvers-tbl">
|
|
<title>View resolvers</title>
|
|
|
|
<tgroup cols="2">
|
|
<colspec colname="c1" colwidth="1*" />
|
|
|
|
<colspec colname="c2" colwidth="2*" />
|
|
|
|
<thead>
|
|
<row>
|
|
<entry><interfacename>ViewResolver</interfacename></entry>
|
|
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><classname>AbstractCachingViewResolver</classname></entry>
|
|
|
|
<entry>Abstract view resolver that caches views. Often views
|
|
need preparation before they can be used; extending this view
|
|
resolver provides caching.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>XmlViewResolver</classname></entry>
|
|
|
|
<entry>Implementation of
|
|
<interfacename>ViewResolver</interfacename> that accepts a
|
|
configuration file written in XML with the same DTD as Spring's
|
|
XML bean factories. The default configuration file is
|
|
<literal>/WEB-INF/views.xml</literal>.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>ResourceBundleViewResolver</classname></entry>
|
|
|
|
<entry>Implementation of
|
|
<interfacename>ViewResolver</interfacename> that uses bean
|
|
definitions in a <classname>ResourceBundle</classname>,
|
|
specified by the bundle base name. Typically you define the
|
|
bundle in a properties file, located in the classpath. <!--Correct to say you define? Seems so, because default implies you can change it.-->The
|
|
default file name is
|
|
<literal>views.properties</literal>.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>UrlBasedViewResolver</classname></entry>
|
|
|
|
<entry>Simple implementation of the
|
|
<interfacename>ViewResolver</interfacename> interface that
|
|
effects the direct resolution of logical view names to URLs,
|
|
without an explicit mapping definition. This is appropriate if
|
|
your logical names match the names of your view resources in a
|
|
straightforward manner, without the need for arbitrary
|
|
mappings.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>InternalResourceViewResolver</classname></entry>
|
|
|
|
<entry>Convenient subclass of
|
|
<classname>UrlBasedViewResolver</classname> that supports
|
|
<classname>InternalResourceView</classname> (in effect, Servlets
|
|
and JSPs) and subclasses such as <classname>JstlView</classname>
|
|
and <classname>TilesView</classname>. You can specify the view
|
|
class for all views generated by this resolver by using
|
|
<literal>setViewClass(..)</literal>. See the Javadocs for the
|
|
<classname>UrlBasedViewResolver</classname> class for
|
|
details.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>VelocityViewResolver</classname> /
|
|
<classname>FreeMarkerViewResolver</classname></entry>
|
|
|
|
<entry>Convenient subclass of
|
|
<classname>UrlBasedViewResolver</classname> that supports
|
|
<classname>VelocityView</classname> (in effect, Velocity
|
|
templates) or <classname>FreeMarkerView</classname>
|
|
,respectively, and custom subclasses of them.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>ContentNegotiatingViewResolver</classname></entry>
|
|
|
|
<entry>Implementation of the
|
|
<interfacename>ViewResolver</interfacename> interface that
|
|
resolves a view based on the request file name or
|
|
<literal>Accept</literal> header. See <xref
|
|
linkend="mvc-multiple-representations" />.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>As an example, with JSP as a view technology, you can use the
|
|
<classname>UrlBasedViewResolver</classname>. This view resolver
|
|
translates a view name to a URL and hands the request over to the
|
|
RequestDispatcher to render the view.</para>
|
|
|
|
<programlisting language="xml"><bean id="viewResolver"
|
|
class="org.springframework.web.servlet.view.UrlBasedViewResolver">
|
|
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
|
|
<property name="prefix" value="/WEB-INF/jsp/"/>
|
|
<property name="suffix" value=".jsp"/>
|
|
</bean></programlisting>
|
|
|
|
<para>When returning <literal>test</literal> as a logical view name,
|
|
this view resolver forwards the request to the
|
|
<classname>RequestDispatcher</classname> that will send the request to
|
|
<literal>/WEB-INF/jsp/test.jsp</literal>.</para>
|
|
|
|
<para>When you combine different view technologies in a web application,
|
|
you can use the
|
|
<classname>ResourceBundleViewResolver</classname>:</para>
|
|
|
|
<programlisting language="xml"><bean id="viewResolver"
|
|
class="org.springframework.web.servlet.view.ResourceBundleViewResolver">
|
|
<property name="basename" value="views"/>
|
|
<property name="defaultParentView" value="parentView"/>
|
|
</bean></programlisting>
|
|
|
|
<para>The <classname>ResourceBundleViewResolver</classname> inspects the
|
|
<classname>ResourceBundle</classname> identified by the basename, and
|
|
for each view it is supposed to resolve, it uses the value of the
|
|
property <literal>[viewname].(class)</literal> as the view class and the
|
|
value of the property <literal>[viewname].url</literal> as the view url.
|
|
Examples can be found in the next chapter which covers view
|
|
technologies. As you can see, you can identify a parent view, from which
|
|
all views in the properties file <quote>extend</quote>. This way you can
|
|
specify a default view class, for example.</para>
|
|
|
|
<note>
|
|
<para>Subclasses of <classname>AbstractCachingViewResolver</classname>
|
|
cache view instances that they resolve. Caching improves performance
|
|
of certain view technologies. It's possible to turn off the cache by
|
|
setting the <literal>cache</literal> property to
|
|
<literal>false</literal>. Furthermore, if you must refresh a certain
|
|
view at runtime (for example when a Velocity template is modified),
|
|
you can use the <literal>removeFromCache(String viewName, Locale
|
|
loc)</literal> method.</para>
|
|
</note>
|
|
</section>
|
|
|
|
<section id="mvc-viewresolver-chaining">
|
|
<title>Chaining ViewResolvers</title>
|
|
|
|
<para>Spring supports multiple view resolvers. Thus you can chain
|
|
resolvers and, for example, override specific views in certain
|
|
circumstances. You chain view resolvers by adding more than one resolver
|
|
to your application context and, if necessary, by setting the
|
|
<literal>order</literal> property to specify ordering. Remember, the
|
|
higher the order property, the later the view resolver is positioned in
|
|
the chain.</para>
|
|
|
|
<para>In the following example, the chain of view resolvers consists of
|
|
two resolvers, an <classname>InternalResourceViewResolver</classname>,
|
|
which is always automatically positioned as the last resolver in the
|
|
chain, and an <classname>XmlViewResolver</classname> for specifying
|
|
Excel views. Excel views are not supported by the
|
|
<classname>InternalResourceViewResolver</classname>.<!--Do you need to say anything else about excel not being supported by one of resolvers? What if anything is the result?--></para>
|
|
|
|
<programlisting language="xml"><bean id="jspViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
|
|
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
|
|
<property name="prefix" value="/WEB-INF/jsp/"/>
|
|
<property name="suffix" value=".jsp"/>
|
|
</bean>
|
|
|
|
<bean id="excelViewResolver" class="org.springframework.web.servlet.view.XmlViewResolver">
|
|
<property name="order" value="1"/>
|
|
<property name="location" value="/WEB-INF/views.xml"/>
|
|
</bean>
|
|
|
|
<lineannotation><!-- in <literal>views.xml</literal> --></lineannotation>
|
|
|
|
<beans>
|
|
<bean name="report" class="org.springframework.example.ReportExcelView"/>
|
|
</beans></programlisting>
|
|
|
|
<para>If a specific view resolver does not result in a view, Spring
|
|
examines the context for other view resolvers. If additional view
|
|
resolvers exist, Spring continues to inspect them until a view is
|
|
resolved. If no view resolver returns a view, Spring throws a
|
|
<classname>ServletException</classname>.</para>
|
|
|
|
<para>The contract of a view resolver specifies that a view resolver
|
|
<emphasis>can</emphasis> return null to indicate the view could not be
|
|
found. Not all view resolvers do this, however, because in some cases,
|
|
the resolver simply cannot detect whether or not the view exists. For
|
|
example, the <classname>InternalResourceViewResolver</classname> uses
|
|
the <classname>RequestDispatcher</classname> internally, and dispatching
|
|
is the only way to figure out if a JSP exists, but this action can only
|
|
execute once. The same holds for the
|
|
<classname>VelocityViewResolver</classname> and some others. Check the
|
|
Javadoc for the view resolver to see whether it reports non-existing
|
|
views. Thus, putting an
|
|
<classname>InternalResourceViewResolver</classname> in the chain in a
|
|
place other than the last, results in the chain not being fully
|
|
inspected, because the
|
|
<classname>InternalResourceViewResolver</classname> will
|
|
<emphasis>always</emphasis> return a view!<!--I don't understand the logic of this. How can it return a view if no view exists or no view can be found? this paragraph is confusing.--><!--Why would you put InternalResourceViewResolver in place other than last? It's automatically last. --></para>
|
|
</section>
|
|
|
|
<section id="mvc-redirecting">
|
|
<title>Redirecting to views<!--Revise to say what you are redirecting to views. OR are you redirecting views? In that case heading should be Redirecting views.--></title>
|
|
|
|
<para>As mentioned previously, a controller typically returns a logical
|
|
view name, which a view resolver resolves to a particular view
|
|
technology. For view technologies such as JSPs that are processed
|
|
through the Servlet or JSP engine, this resolution is usually handled
|
|
through the combination of
|
|
<classname>InternalResourceViewResolver</classname> and
|
|
<classname>InternalResourceView</classname>, which issues an internal
|
|
forward or include via the Servlet API's
|
|
<literal>RequestDispatcher.forward(..)</literal> method or
|
|
<literal>RequestDispatcher.include()</literal> method. For other view
|
|
technologies, such as Velocity, XSLT, and so on, the view itself writes
|
|
the content directly to the response stream.</para>
|
|
|
|
<para>It is sometimes desirable to issue an HTTP redirect back to the
|
|
client, before the view is rendered. This is desirable, for example,
|
|
when one controller has been called with <literal>POST</literal>ed data,
|
|
and the response is actually a delegation to another controller (for
|
|
example on a successful form submission). In this case, a normal
|
|
internal forward will mean that the other controller will also see the
|
|
same <literal>POST</literal> data, which is potentially problematic if
|
|
it can confuse it with other expected data. Another reason to perform a
|
|
redirect before displaying the result is to eliminate the possibility of
|
|
the user submitting the form data multiple times. In this scenario, the
|
|
browser will first send an initial <literal>POST</literal>; it will then
|
|
receive a response to redirect to a different URL; and finally the
|
|
browser will perform a subsequent <literal>GET</literal> for the URL
|
|
named in the redirect response. Thus, from the perspective of the
|
|
browser, the current page does not reflect the result of a
|
|
<literal>POST</literal> but rather of a <literal>GET</literal>. The end
|
|
effect is that there is no way the user can accidentally
|
|
re-<literal>POST</literal> the same data by performing a refresh. The
|
|
refresh forces a <literal>GET</literal> of the result page, not a resend
|
|
of the initial <literal>POST</literal> data.</para>
|
|
|
|
<section id="mvc-redirecting-redirect-view">
|
|
<title><classname>RedirectView</classname></title>
|
|
|
|
<para>One way to force a redirect as the result of a controller
|
|
response is for the controller to create and return an instance of
|
|
Spring's <classname>RedirectView</classname>. In this case,
|
|
<classname>DispatcherServlet</classname> does not use the normal view
|
|
resolution mechanism. Rather because it has been given the (redirect)
|
|
view already, the <classname>DispatcherServlet</classname> simply
|
|
instructs the view to do its work.</para>
|
|
|
|
<para>The <classname>RedirectView</classname> issues an
|
|
<literal>HttpServletResponse.sendRedirect()</literal> call that
|
|
returns to the client browser as an HTTP redirect. By default all
|
|
model attributes are considered to be exposed as URI template
|
|
variables in the redirect URL. Of the remaining attributes those that
|
|
are primitive types or collections/arrays of primitive types are
|
|
automatically appended as query parameters.</para>
|
|
|
|
<para>Appending primitive type attributes as query parameters may be
|
|
the desired result if a model instance was prepared specifically for
|
|
the redirect. However, in annotated controllers the model may contain
|
|
additional attributes added for rendering purposes (e.g. drop-down
|
|
field values). To avoid the possibility of having such attributes
|
|
appear in the URL an annotated controller can declare an argument of
|
|
type <interfacename>RedirectAttributes</interfacename> and use it to
|
|
specify the exact attributes to make available to
|
|
<classname>RedirectView</classname>. If the controller method decides
|
|
to redirect, the content of
|
|
<interfacename>RedirectAttributes</interfacename> is used. Otherwise
|
|
the content of the model is used.</para>
|
|
|
|
<para>Note that URI template variables from the present request are
|
|
automatically made available when expanding a redirect URL and do not
|
|
need to be added explicitly neither through
|
|
<interfacename>Model</interfacename> nor
|
|
<interfacename>RedirectAttributes</interfacename>. For example:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value = "/files/{path}", method = RequestMethod.POST)
|
|
public String upload(...) {
|
|
// ...
|
|
return "redirect:files/{path}";
|
|
}</programlisting>
|
|
|
|
<para>If you use <classname>RedirectView</classname> and the view is
|
|
created by the controller itself, it is recommended that you configure
|
|
the redirect URL to be injected into the controller so that it is not
|
|
baked into the controller but configured in the context along with the
|
|
view names. The next section discusses this process.</para>
|
|
</section>
|
|
|
|
<section id="mvc-redirecting-redirect-prefix">
|
|
<title>The <literal>redirect:</literal> prefix</title>
|
|
|
|
<para>While the use of <classname>RedirectView</classname> works fine,
|
|
if the controller itself creates the
|
|
<classname>RedirectView</classname>, there is no avoiding the fact
|
|
that the controller is aware that a redirection is happening. This is
|
|
really suboptimal and couples things too tightly. The controller
|
|
should not really care about how the response gets handled. In general
|
|
it should operate only in terms of view names that have been injected
|
|
into it.</para>
|
|
|
|
<para>The special <literal>redirect:</literal> prefix allows you to
|
|
accomplish this. If a view name is returned that has the prefix
|
|
<literal>redirect:</literal>, the
|
|
<classname>UrlBasedViewResolver</classname> (and all subclasses) will
|
|
recognize this as a special indication that a redirect is needed. The
|
|
rest of the view name will be treated as the redirect URL.</para>
|
|
|
|
<para>The net effect is the same as if the controller had returned a
|
|
<classname>RedirectView</classname>, but now the controller itself can
|
|
simply operate in terms of logical view names. A logical view name
|
|
such as <literal>redirect:/myapp/some/resource</literal> will redirect
|
|
relative to the current Servlet context, while a name such as
|
|
<literal>redirect:http://myhost.com/some/arbitrary/path</literal> will
|
|
redirect to an absolute URL.</para>
|
|
</section>
|
|
|
|
<section id="mvc-redirecting-forward-prefix">
|
|
<title>The <literal>forward:</literal> prefix<!--Can you revise this heading to say what you're using the forward prefix to accomplish?--></title>
|
|
|
|
<para>It is also possible to use a special <literal>forward:</literal>
|
|
prefix for view names that are ultimately resolved by
|
|
<classname>UrlBasedViewResolver</classname> and subclasses. This
|
|
creates an <classname>InternalResourceView</classname> (which
|
|
ultimately does a <literal>RequestDispatcher.forward()</literal>)
|
|
around the rest of the view name, which is considered a URL.
|
|
Therefore, this prefix is not useful with
|
|
<classname>InternalResourceViewResolver</classname> and
|
|
<classname>InternalResourceView</classname> (for JSPs for example).
|
|
But the prefix can be helpful when you are primarily using another
|
|
view technology, but still want to force a forward of a resource to be
|
|
handled by the Servlet/JSP engine. (Note that you may also chain
|
|
multiple view resolvers, instead.)<!--I think the preceding sentences were a bit garbled. I tried to reword a bit. And is this paragraph logical?--></para>
|
|
|
|
<para>As with the <literal>redirect:</literal> prefix, if the view
|
|
name with the <literal>forward:</literal> prefix is injected into the
|
|
controller, the controller does not detect that anything special is
|
|
happening in terms of handling the response.<!--Can you reword to clarify the point? The controller does not detect what?--></para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-multiple-representations">
|
|
<title><classname>ContentNegotiatingViewResolver</classname></title>
|
|
|
|
<para>The <classname>ContentNegotiatingViewResolver</classname> does not
|
|
resolve views itself but rather delegates to other view resolvers,
|
|
selecting the view that resembles the representation requested by the
|
|
client. Two strategies exist for a client to request a representation
|
|
from the server:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Use a distinct URI for each resource, typically by using a
|
|
different file extension in the URI. For example, the URI<literal>
|
|
http://www.example.com/users/fred.pdf</literal> requests a PDF
|
|
representation of the user fred, and
|
|
<literal>http://www.example.com/users/fred.xml</literal> requests an
|
|
XML representation.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Use the same URI for the client to locate the resource, but
|
|
set the <literal>Accept</literal> HTTP request header to list the
|
|
<ulink url="http://en.wikipedia.org/wiki/Internet_media_type">media
|
|
types</ulink> that it understands. For example, an HTTP request for
|
|
<literal>http://www.example.com/users/fred</literal> with an
|
|
<literal>Accept</literal> header set to <literal>application/pdf
|
|
</literal>requests a PDF representation of the user fred, while
|
|
<literal>http://www.example.com/users/fred</literal> with an
|
|
<literal>Accept</literal> header set to <literal>text/xml</literal>
|
|
requests an XML representation. This strategy is known as <ulink
|
|
url="http://en.wikipedia.org/wiki/Content_negotiation">content
|
|
negotiation</ulink>.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<note>
|
|
<para>One issue with the <literal>Accept</literal> header is that it
|
|
is impossible to set it in a web browser within HTML. For example, in
|
|
Firefox, it is fixed to:<!--So how would you set the Accept header as in second bullet, if you can't do it in html? Indicate?--></para>
|
|
|
|
<programlisting>Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8</programlisting>
|
|
|
|
<para>For this reason it is common to see the use of a distinct URI
|
|
for each representation when developing browser based web
|
|
applications.</para>
|
|
</note>
|
|
|
|
<para>To support multiple representations of a resource, Spring provides
|
|
the <classname>ContentNegotiatingViewResolver</classname> to resolve a
|
|
view based on the file extension or <literal>Accept</literal> header of
|
|
the HTTP request. <classname>ContentNegotiatingViewResolver</classname>
|
|
does not perform the view resolution itself but instead delegates to a
|
|
list of view resolvers that you specify through the bean property
|
|
<literal>ViewResolvers</literal>.<!--A human has to specify this list of resolvers, right? See example below.--></para>
|
|
|
|
<para>The <classname>ContentNegotiatingViewResolver</classname> selects
|
|
an appropriate <classname>View</classname> to handle the request by
|
|
comparing the request media type(s) with the media type (also known as
|
|
<literal>Content-Type</literal>) supported by the
|
|
<classname>View</classname> associated with each of its
|
|
<classname>ViewResolvers</classname>. The first
|
|
<classname>View</classname> in the list that has a compatible
|
|
<literal>Content-Type</literal> returns the representation to the
|
|
client. If a compatible view cannot be supplied by the
|
|
<classname>ViewResolver</classname> chain, then the list of views
|
|
specified through the <literal>DefaultViews</literal> property will be
|
|
consulted. This latter option is appropriate for singleton
|
|
<classname>Views</classname> that can render an appropriate
|
|
representation of the current resource regardless of the logical view
|
|
name. The <literal>Accept</literal> header may include wild cards, for
|
|
example <literal>text/*</literal>, in which case a
|
|
<classname>View</classname> whose Content-Type was
|
|
<literal>text/xml</literal> is a compatible match.</para>
|
|
|
|
<para>To support the resolution of a view based on a file extension, use
|
|
the <classname>ContentNegotiatingViewResolver </classname>bean property
|
|
<literal>mediaTypes</literal> to specify a mapping of file extensions to
|
|
media types. For more information on the algorithm used to determine the
|
|
request media type, refer to the API documentation for
|
|
<classname>ContentNegotiatingViewResolver</classname>.</para>
|
|
|
|
<para>Here is an example configuration of a
|
|
<classname>ContentNegotiatingViewResolver:</classname></para>
|
|
|
|
<programlisting language="xml"><bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
|
|
<property name="mediaTypes">
|
|
<map>
|
|
<entry key="atom" value="application/atom+xml"/>
|
|
<entry key="html" value="text/html"/>
|
|
<entry key="json" value="application/json"/>
|
|
</map>
|
|
</property>
|
|
<property name="viewResolvers">
|
|
<list>
|
|
<bean class="org.springframework.web.servlet.view.BeanNameViewResolver"/>
|
|
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
|
|
<property name="prefix" value="/WEB-INF/jsp/"/>
|
|
<property name="suffix" value=".jsp"/>
|
|
</bean>
|
|
</list>
|
|
</property>
|
|
<property name="defaultViews">
|
|
<list>
|
|
<bean class="org.springframework.web.servlet.view.json.MappingJackson2JsonView" />
|
|
</list>
|
|
</property>
|
|
</bean>
|
|
|
|
|
|
<bean id="content" class="com.springsource.samples.rest.SampleContentAtomView"/></programlisting>
|
|
|
|
<para>The <classname>InternalResourceViewResolver</classname> handles
|
|
the translation of view names and JSP pages, while the
|
|
<classname>BeanNameViewResolver</classname> returns a view based on the
|
|
name of a bean. (See "<link
|
|
linkend="mvc-viewresolver-resolver">Resolving views with the
|
|
ViewResolver interface</link>" for more details on how Spring looks up
|
|
and instantiates a view.) In this example, the
|
|
<literal>content</literal> bean is a class that inherits from
|
|
<classname>AbstractAtomFeedView</classname>, which returns an Atom RSS
|
|
feed. For more information on creating an Atom Feed representation, see
|
|
the section Atom Views.<!--Need a correct link or x-ref re the preceding sentence.I couldn't find an "Atom Views" section.--></para>
|
|
|
|
<para>In the above configuration, if a request is made with an
|
|
<literal>.html</literal> extension, the view resolver looks for a view
|
|
that matches the <literal>text/html</literal> media type. The
|
|
<classname>InternalResourceViewResolver</classname> provides the
|
|
matching view for <literal>text/html</literal>. If the request is made
|
|
with the file extension <literal>.atom</literal>, the view resolver
|
|
looks for a view that matches the
|
|
<literal>application/atom+xml</literal> media type. This view is
|
|
provided by the <classname>BeanNameViewResolver</classname> that maps to
|
|
the <classname>SampleContentAtomView</classname> if the view name
|
|
returned is <classname>content</classname>. If the request is made with
|
|
the file extension <literal>.json</literal>, the
|
|
<classname>MappingJackson2JsonView</classname>instance from the
|
|
<literal>DefaultViews</literal> list will be selected regardless of the
|
|
view name. Alternatively, client requests can be made without a file
|
|
extension but with the <literal>Accept</literal> header set to the
|
|
preferred media-type, and the same resolution of request to views would
|
|
occur.<!--Can you reword preceding sentence? I don't follow it.--></para>
|
|
|
|
<note>
|
|
<para>If <classname>ContentNegotiatingViewResolver</classname>'s list
|
|
of ViewResolvers is not configured explicitly, it automatically uses
|
|
any ViewResolvers defined in the application context.</para>
|
|
</note>
|
|
|
|
<para>The corresponding controller code that returns an Atom RSS feed
|
|
for a URI of the form <literal>http://localhost/content.atom</literal>
|
|
or <literal>http://localhost/content</literal> with an
|
|
<literal>Accept</literal> header of application/atom+xml is shown
|
|
below.</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class ContentController {
|
|
|
|
private List<SampleContent> contentList = new ArrayList<SampleContent>();
|
|
|
|
@RequestMapping(value="/content", method=RequestMethod.GET)
|
|
public ModelAndView getContent() {
|
|
ModelAndView mav = new ModelAndView();
|
|
mav.setViewName("content");
|
|
mav.addObject("sampleContentList", contentList);
|
|
return mav;
|
|
}
|
|
|
|
}</programlisting>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-flash-attributes">
|
|
<title>Using flash attributes</title>
|
|
|
|
<para>Flash attributes provide a way for one request to store attributes
|
|
intended for use in another. This is most commonly needed when redirecting
|
|
— for example, the <emphasis>Post/Redirect/Get</emphasis> pattern. Flash
|
|
attributes are saved temporarily before the redirect (typically in the
|
|
session) to be made available to the request after the redirect and
|
|
removed immediately.</para>
|
|
|
|
<para>Spring MVC has two main abstractions in support of flash attributes.
|
|
<classname>FlashMap</classname> is used to hold flash attributes while
|
|
<interfacename>FlashMapManager</interfacename> is used to store, retrieve,
|
|
and manage <classname>FlashMap</classname> instances.</para>
|
|
|
|
<para>Flash attribute support is always "on" and does not need to enabled
|
|
explicitly although if not used, it never causes HTTP session creation. On
|
|
each request there is an "input" <classname>FlashMap</classname> with
|
|
attributes passed from a previous request (if any) and an "output"
|
|
<classname>FlashMap</classname> with attributes to save for a subsequent
|
|
request. Both <classname>FlashMap</classname> instances are accessible
|
|
from anywhere in Spring MVC through static methods in
|
|
<classname>RequestContextUtils</classname>.</para>
|
|
|
|
<para>Annotated controllers typically do not need to work with
|
|
<classname>FlashMap</classname> directly. Instead an
|
|
<interfacename>@RequestMapping</interfacename> method can accept an
|
|
argument of type <interfacename>RedirectAttributes</interfacename> and use
|
|
it to add flash attributes for a redirect scenario. Flash attributes added
|
|
via <interfacename>RedirectAttributes</interfacename> are automatically
|
|
propagated to the "output" FlashMap. Similarly after the redirect
|
|
attributes from the "input" <classname>FlashMap</classname> are
|
|
automatically added to the <interfacename>Model</interfacename> of the
|
|
controller serving the target URL.</para>
|
|
|
|
<sidebar id="mvc-flash-attributes-concurrency">
|
|
<title>Matching requests to flash attributes</title>
|
|
|
|
<para>The concept of flash attributes exists in many other Web
|
|
frameworks and has proven to be exposed sometimes to concurrency issues.
|
|
This is because by definition flash attributes are to be stored until
|
|
the next request. However the very "next" request may not be the
|
|
intended recipient but another asynchronous request (e.g. polling or
|
|
resource requests) in which case the flash attributes are removed too
|
|
early.</para>
|
|
|
|
<para>To reduce the possibility of such issues,
|
|
<classname>RedirectView</classname> automatically "stamps"
|
|
<classname>FlashMap</classname> instances with the path and query
|
|
parameters of the target redirect URL. In turn the default
|
|
<classname>FlashMapManager</classname> matches that information to
|
|
incoming requests when looking up the "input"
|
|
<classname>FlashMap</classname>.</para>
|
|
|
|
<para>This does not eliminate the possibility of a concurrency issue
|
|
entirely but nevertheless reduces it greatly with information that is
|
|
already available in the redirect URL. Therefore the use of flash
|
|
attributes is recommended mainly for redirect scenarios .</para>
|
|
</sidebar>
|
|
</section>
|
|
|
|
<section id="mvc-construct-encode-uri">
|
|
<title>Building <literal>URI</literal>s</title>
|
|
|
|
<para>Spring MVC provides a mechanism for building and encoding a URI
|
|
using <classname>UriComponentsBuilder</classname> and
|
|
<classname>UriComponents</classname>.
|
|
</para>
|
|
|
|
<para>For example you can expand and encode a URI template string:</para>
|
|
|
|
<programlisting language="java">UriComponents uriComponents =
|
|
UriComponentsBuilder.fromUriString("http://example.com/hotels/{hotel}/bookings/{booking}").build();
|
|
|
|
URI uri = uriComponents.expand("42", "21").encode().toUri();
|
|
</programlisting>
|
|
|
|
<para>Note that <classname>UriComponents</classname> is immutable and
|
|
the <literal>expand()</literal> and <literal>encode()</literal>
|
|
operations return new instances if necessary.</para>
|
|
|
|
<para>You can also expand and encode using individual URI components:</para>
|
|
|
|
<programlisting language="java">UriComponents uriComponents =
|
|
UriComponentsBuilder.newInstance()
|
|
.scheme("http").host("example.com").path("/hotels/{hotel}/bookings/{booking}").build()
|
|
.expand("42", "21")
|
|
.encode();
|
|
</programlisting>
|
|
|
|
<para>In a Servlet environment the
|
|
<classname>ServletUriComponentsBuilder</classname> sub-class provides
|
|
static factory methods to copy available URL information from a
|
|
Servlet requests:
|
|
</para>
|
|
|
|
<programlisting language="java">HttpServletRequest request = ...
|
|
|
|
// Re-use host, scheme, port, path and query string
|
|
// Replace the "accountId" query param
|
|
|
|
ServletUriComponentsBuilder ucb =
|
|
ServletUriComponentsBuilder.fromRequest(request).replaceQueryParam("accountId", "{id}").build()
|
|
.expand("123")
|
|
.encode();
|
|
</programlisting>
|
|
|
|
<para>Alternatively, you may choose to copy a subset of the available
|
|
information up to and including the context path:</para>
|
|
|
|
<programlisting language="java">// Re-use host, port and context path
|
|
// Append "/accounts" to the path
|
|
|
|
ServletUriComponentsBuilder ucb =
|
|
ServletUriComponentsBuilder.fromContextPath(request).path("/accounts").build()
|
|
</programlisting>
|
|
|
|
<para>Or in cases where the <classname>DispatcherServlet</classname> is mapped
|
|
by name (e.g. <literal>/main/*</literal>), you can also have the literal part
|
|
of the servlet mapping included:</para>
|
|
|
|
<programlisting language="java">// Re-use host, port, context path
|
|
// Append the literal part of the servlet mapping to the path
|
|
// Append "/accounts" to the path
|
|
|
|
ServletUriComponentsBuilder ucb =
|
|
ServletUriComponentsBuilder.fromServletMapping(request).path("/accounts").build()
|
|
</programlisting>
|
|
|
|
</section>
|
|
|
|
<section id="mvc-localeresolver">
|
|
<title>Using locales</title>
|
|
|
|
<para>Most parts of Spring's architecture support internationalization,
|
|
just as the Spring web MVC framework does.
|
|
<classname>DispatcherServlet</classname> enables you to automatically
|
|
resolve messages using the client's locale. This is done with
|
|
<interfacename>LocaleResolver</interfacename> objects.</para>
|
|
|
|
<para>When a request comes in, the
|
|
<classname>DispatcherServlet</classname> looks for a locale resolver, and
|
|
if it finds one it tries to use it to set the locale. Using the
|
|
<literal>RequestContext.getLocale()</literal> method, you can always
|
|
retrieve the locale that was resolved by the locale resolver.</para>
|
|
|
|
<para>In addition to automatic locale resolution, you can also attach an
|
|
interceptor to the handler mapping (see <xref
|
|
linkend="mvc-handlermapping-interceptor" /> for more information on
|
|
handler mapping interceptors) to change the locale under specific
|
|
circumstances, for example, based on a parameter in the request.</para>
|
|
|
|
<para>Locale resolvers and interceptors are defined in the
|
|
<literal>org.springframework.web.servlet.i18n</literal> package and are
|
|
configured in your application context in the normal way. Here is a
|
|
selection of the locale resolvers included in Spring.</para>
|
|
|
|
<section id="mvc-localeresolver-acceptheader">
|
|
<title><classname>AcceptHeaderLocaleResolver</classname></title>
|
|
|
|
<para>This locale resolver inspects the
|
|
<literal>accept-language</literal> header in the request that was sent
|
|
by the client (e.g., a web browser). Usually this header field contains
|
|
the locale of the client's operating system.</para>
|
|
</section>
|
|
|
|
<section id="mvc-localeresolver-cookie">
|
|
<title><classname>CookieLocaleResolver</classname></title>
|
|
|
|
<para>This locale resolver inspects a <classname>Cookie</classname> that
|
|
might exist on the client to see if a locale is specified. If so, it
|
|
uses the specified locale. Using the properties of this locale resolver,
|
|
you can specify the name of the cookie as well as the maximum age. Find
|
|
below an example of defining a
|
|
<classname>CookieLocaleResolver</classname>.</para>
|
|
|
|
<programlisting language="xml"><bean id="localeResolver" class="org.springframework.web.servlet.i18n.CookieLocaleResolver">
|
|
|
|
<property name="cookieName" value="clientlanguage"/>
|
|
|
|
<lineannotation><!-- in seconds. If set to <literal>-1</literal>, the cookie is not persisted (deleted when browser shuts down) --></lineannotation>
|
|
<property name="cookieMaxAge" value="100000">
|
|
|
|
</bean></programlisting>
|
|
|
|
<table id="mvc-cookie-locale-resolver-props-tbl">
|
|
<title><classname>CookieLocaleResolver</classname> properties</title>
|
|
|
|
<tgroup cols="3">
|
|
<colspec colname="c1" colwidth="1*" />
|
|
|
|
<colspec colname="c2" colwidth="1*" />
|
|
|
|
<colspec colname="c3" colwidth="3*" />
|
|
|
|
<thead>
|
|
<row>
|
|
<entry>Property</entry>
|
|
|
|
<entry>Default</entry>
|
|
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry>cookieName</entry>
|
|
|
|
<entry>classname + LOCALE</entry>
|
|
|
|
<entry>The name of the cookie</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>cookieMaxAge</entry>
|
|
|
|
<entry>Integer.MAX_INT</entry>
|
|
|
|
<entry>The maximum time a cookie will stay persistent on the
|
|
client. If -1 is specified, the cookie will not be persisted; it
|
|
will only be available until the client shuts down his or her
|
|
browser.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>cookiePath</entry>
|
|
|
|
<entry>/</entry>
|
|
|
|
<entry>Limits the visibility of the cookie to a certain part of
|
|
your site. When cookiePath is specified, the cookie will only be
|
|
visible to that path and the paths below it.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
</section>
|
|
|
|
<section id="mvc-localeresolver-session">
|
|
<title><classname>SessionLocaleResolver</classname></title>
|
|
|
|
<para>The <classname>SessionLocaleResolver</classname> allows you to
|
|
retrieve locales from the session that might be associated with the
|
|
user's request.<!--Aren't you missing some information and example? This section has only one sentence.--></para>
|
|
</section>
|
|
|
|
<section id="mvc-localeresolver-interceptor">
|
|
<title><classname>LocaleChangeInterceptor</classname></title>
|
|
|
|
<para>You can enable changing of locales by adding the
|
|
<classname>LocaleChangeInterceptor</classname> to one of the handler
|
|
mappings (see <xref linkend="mvc-handlermapping" />). It will detect a
|
|
parameter in the request and change the locale. It calls
|
|
<literal>setLocale()</literal> on the
|
|
<interfacename>LocaleResolver</interfacename> that also exists in the
|
|
context. The following example shows that calls to all
|
|
<literal>*.view</literal> resources containing a parameter named
|
|
<literal>siteLanguage</literal> will now change the locale. So, for
|
|
example, a request for the following URL,
|
|
<literal>http://www.sf.net/home.view?siteLanguage=nl</literal> will
|
|
change the site language to Dutch.</para>
|
|
|
|
<programlisting language="xml"><bean id="localeChangeInterceptor"
|
|
class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">
|
|
<property name="paramName" value="siteLanguage"/>
|
|
</bean>
|
|
|
|
<bean id="localeResolver"
|
|
class="org.springframework.web.servlet.i18n.CookieLocaleResolver"/>
|
|
|
|
<bean id="urlMapping"
|
|
class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
|
|
<property name="interceptors">
|
|
<list>
|
|
<ref bean="localeChangeInterceptor"/>
|
|
</list>
|
|
</property>
|
|
<property name="mappings">
|
|
<value>/**/*.view=someController</value>
|
|
</property>
|
|
</bean></programlisting>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-themeresolver">
|
|
<title>Using themes</title>
|
|
|
|
<section id="mvc-themeresolver-introduction">
|
|
<title>Overview of themes</title>
|
|
|
|
<para>You can apply Spring Web MVC framework themes to set the overall
|
|
look-and-feel of your application, thereby enhancing user experience. A
|
|
theme is a collection of static resources, typically style sheets and
|
|
images, that affect the visual style of the application.</para>
|
|
</section>
|
|
|
|
<section id="mvc-themeresolver-defining">
|
|
<title>Defining themes</title>
|
|
|
|
<para>To use themes in your web application, you must set up an
|
|
implementation of the
|
|
<interfacename>org.springframework.ui.context.ThemeSource</interfacename>
|
|
interface. The <interfacename>WebApplicationContext</interfacename>
|
|
interface extends <interfacename>ThemeSource</interfacename> but
|
|
delegates its responsibilities to a dedicated implementation. By default
|
|
the delegate will be an
|
|
<classname>org.springframework.ui.context.support.ResourceBundleThemeSource</classname>
|
|
implementation that loads properties files from the root of the
|
|
classpath. To use a custom <interfacename>ThemeSource</interfacename>
|
|
implementation or to configure the base name prefix of the
|
|
<classname>ResourceBundleThemeSource</classname>, you can register a
|
|
bean in the application context with the reserved name
|
|
<classname>themeSource</classname>. The web application context
|
|
automatically detects a bean with that name and uses it.</para>
|
|
|
|
<para>When using the <classname>ResourceBundleThemeSource</classname>, a
|
|
theme is defined in a simple properties file. <!--Revise preceding sentence to clarify: To use ResourceBundleThemeSource, you define a theme in a properties file? OR do you mean a theme--><!--is already defined in a simple properties file for use with ResourceBundleThemeSource?-->The
|
|
properties file lists the resources that make up the theme. Here is an
|
|
example:<!--Is this an example of what a human enters? If not, why is it referred to as an example, if this is exact code already provided?--></para>
|
|
|
|
<programlisting>styleSheet=/themes/cool/style.css
|
|
background=/themes/cool/img/coolBg.jpg</programlisting>
|
|
|
|
<para>The keys of the properties are the names that refer to the themed
|
|
elements from view code. For a JSP, you typically do this using the
|
|
<literal>spring:theme</literal> custom tag, which is very similar to the
|
|
<literal>spring:message</literal> tag. The following JSP fragment uses
|
|
the theme defined in the previous example to customize the look and
|
|
feel:</para>
|
|
|
|
<programlisting language="xml"><%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>
|
|
<html>
|
|
<head>
|
|
<link rel="stylesheet" href="<spring:theme code='styleSheet'/>" type="text/css"/>
|
|
</head>
|
|
<body style="background=<spring:theme code='background'/>">
|
|
...
|
|
</body>
|
|
</html></programlisting>
|
|
|
|
<para>By default, the <classname>ResourceBundleThemeSource</classname>
|
|
uses an empty base name prefix. As a result, the properties files are
|
|
loaded from the root of the classpath. Thus you would put the
|
|
<literal>cool.properties</literal> theme definition in a directory at
|
|
the root of the classpath, for example, in
|
|
<literal>/WEB-INF/classes</literal>. The
|
|
<classname>ResourceBundleThemeSource</classname> uses the standard Java
|
|
resource bundle loading mechanism, allowing for full
|
|
internationalization of themes. For example, we could have a
|
|
<literal>/WEB-INF/classes/cool_nl.properties</literal> that references a
|
|
special background image with Dutch text on it.</para>
|
|
</section>
|
|
|
|
<section id="mvc-themeresolver-resolving">
|
|
<title>Theme resolvers</title>
|
|
|
|
<para>After you define themes, as in the preceding section, you decide
|
|
which theme to use. The <classname>DispatcherServlet</classname> will
|
|
look for a bean named <classname>themeResolver</classname> to find out
|
|
which <interfacename>ThemeResolver</interfacename> implementation to
|
|
use. A theme resolver works in much the same way as a
|
|
<interfacename>LocaleResolver</interfacename>. It detects the theme to
|
|
use for a particular request and can also alter the request's theme. The
|
|
following theme resolvers are provided by Spring:</para>
|
|
|
|
<table id="mvc-theme-resolver-impls-tbl">
|
|
<title><interfacename>ThemeResolver</interfacename>
|
|
implementations</title>
|
|
|
|
<tgroup cols="2">
|
|
<colspec colname="c1" colwidth="1*" />
|
|
|
|
<colspec colname="c3" colwidth="3*" />
|
|
|
|
<thead>
|
|
<row>
|
|
<entry>Class</entry>
|
|
|
|
<entry>Description</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><classname>FixedThemeResolver</classname></entry>
|
|
|
|
<entry>Selects a fixed theme, set using the
|
|
<classname>defaultThemeName</classname> property.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>SessionThemeResolver</classname></entry>
|
|
|
|
<entry>The theme is maintained in the user's HTTP session. It
|
|
only needs to be set once for each session, but is not persisted
|
|
between sessions.</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>CookieThemeResolver</classname></entry>
|
|
|
|
<entry>The selected theme is stored in a cookie on the
|
|
client.</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>Spring also provides a
|
|
<classname>ThemeChangeInterceptor</classname> that allows theme changes
|
|
on every request with a simple request parameter.<!--Do you need more info or an example re preceding sentence?--></para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-multipart">
|
|
<title>Spring's multipart (file upload) support</title>
|
|
|
|
<section id="mvc-multipart-introduction">
|
|
<title>Introduction</title>
|
|
|
|
<para>Spring's built-in multipart support handles file uploads in web
|
|
applications. You enable this multipart support with pluggable
|
|
<interfacename>MultipartResolver</interfacename> objects, defined in the
|
|
<literal>org.springframework.web.multipart</literal> package. Spring
|
|
provides one <interfacename>MultipartResolver</interfacename>
|
|
implementation for use with <ulink
|
|
url="http://jakarta.apache.org/commons/fileupload"> <emphasis>Commons
|
|
FileUpload</emphasis></ulink> and another for use with Servlet 3.0
|
|
multipart request parsing.</para>
|
|
|
|
<para>By default, Spring does no multipart handling, because some
|
|
developers want to handle multiparts themselves. You enable Spring
|
|
multipart handling by adding a multipart resolver to the web
|
|
application's context. Each request is inspected to see if it contains a
|
|
multipart. If no multipart is found, the request continues as expected.
|
|
If a multipart is found in the request, the
|
|
<classname>MultipartResolver</classname> that has been declared in your
|
|
context is used. After that, the multipart attribute in your request is
|
|
treated like any other attribute.</para>
|
|
</section>
|
|
|
|
<section id="mvc-multipart-resolver-commons">
|
|
<title>Using a <interfacename>MultipartResolver</interfacename> with
|
|
<emphasis>Commons FileUpload</emphasis></title>
|
|
|
|
<para>The following example shows how to use the
|
|
<classname>CommonsMultipartResolver</classname>:</para>
|
|
|
|
<programlisting language="xml"><bean id="multipartResolver"
|
|
class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
|
|
|
|
<lineannotation><!-- one of the properties available; the maximum file size in bytes --></lineannotation>
|
|
<property name="maxUploadSize" value="100000"/>
|
|
</bean></programlisting>
|
|
|
|
<para>Of course you also need to put the appropriate jars in your
|
|
classpath for the multipart resolver to work. In the case of the
|
|
<classname>CommonsMultipartResolver</classname>, you need to use
|
|
<literal>commons-fileupload.jar</literal>.</para>
|
|
|
|
<para>When the Spring <classname>DispatcherServlet</classname> detects a
|
|
multi-part request, it activates the resolver that has been declared in
|
|
your context and hands over the request. The resolver then wraps the
|
|
current <classname>HttpServletRequest</classname> into a
|
|
<classname>MultipartHttpServletRequest</classname> that supports
|
|
multipart file uploads. Using the
|
|
<classname>MultipartHttpServletRequest</classname>, you can get
|
|
information about the multiparts contained by this request and actually
|
|
get access to the multipart files themselves in your controllers.</para>
|
|
</section>
|
|
|
|
<section id="mvc-multipart-resolver-standard">
|
|
<title>Using a <interfacename>MultipartResolver</interfacename> with
|
|
<emphasis>Servlet 3.0</emphasis></title>
|
|
|
|
<para>In order to use Servlet 3.0 based multipart parsing, you need to
|
|
mark the <classname>DispatcherServlet</classname> with a
|
|
<literal>"multipart-config"</literal> section in
|
|
<filename>web.xml</filename>, or with a
|
|
<classname>javax.servlet.MultipartConfigElement</classname> in
|
|
programmatic Servlet registration, or in case of a custom Servlet class
|
|
possibly with a
|
|
<classname>javax.servlet.annotation.MultipartConfig</classname>
|
|
annotation on your Servlet class. Configuration settings such as maximum
|
|
sizes or storage locations need to be applied at that Servlet
|
|
registration level as Servlet 3.0 does not allow for those settings to
|
|
be done from the MultipartResolver.</para>
|
|
|
|
<para>Once Servlet 3.0 multipart parsing has been enabled in one of the
|
|
above mentioned ways you can add the
|
|
<classname>StandardServletMultipartResolver</classname> to your Spring
|
|
configuration:</para>
|
|
|
|
<programlisting language="xml"><bean id="multipartResolver"
|
|
class="org.springframework.web.multipart.support.StandardServletMultipartResolver">
|
|
</bean></programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-multipart-forms">
|
|
<title>Handling a file upload in a form</title>
|
|
|
|
<para>After the <classname>MultipartResolver</classname> completes its
|
|
job, the request is processed like any other. First, create a form with
|
|
a file input that will allow the user to upload a form. The encoding
|
|
attribute (<literal>enctype="multipart/form-data"</literal>) lets the
|
|
browser know how to encode the form as multipart request:</para>
|
|
|
|
<programlisting language="xml"><html>
|
|
<head>
|
|
<title>Upload a file please</title>
|
|
</head>
|
|
<body>
|
|
<h1>Please upload a file</h1>
|
|
<form method="post" action="/form" enctype="multipart/form-data">
|
|
<input type="text" name="name"/>
|
|
<input type="file" name="file"/>
|
|
<input type="submit"/>
|
|
</form>
|
|
</body>
|
|
</html></programlisting>
|
|
|
|
<para>The next step is to create a controller that handles the file
|
|
upload. This controller is very similar to a <link
|
|
linkend="mvc-ann-controller">normal annotated
|
|
<interfacename>@Controller</interfacename></link>, except that we use
|
|
<classname>MultipartHttpServletRequest</classname> or
|
|
<filename>MultipartFile</filename> in the method parameters:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class FileUploadController {
|
|
|
|
@RequestMapping(value = "/form", method = RequestMethod.POST)
|
|
public String handleFormUpload(@RequestParam("name") String name,
|
|
@RequestParam("file") MultipartFile file) {
|
|
|
|
if (!file.isEmpty()) {
|
|
byte[] bytes = file.getBytes();
|
|
<lineannotation>// store the bytes somewhere</lineannotation>
|
|
return "redirect:uploadSuccess";
|
|
} else {
|
|
return "redirect:uploadFailure";
|
|
}
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>Note how the <interfacename>@RequestParam</interfacename> method
|
|
parameters map to the input elements declared in the form. In this
|
|
example, nothing is done with the <literal>byte[]</literal>, but in
|
|
practice you can save it in a database, store it on the file system, and
|
|
so on.</para>
|
|
|
|
<para>When using Servlet 3.0 multipart parsing you can also use
|
|
<classname>javax.servlet.http.Part</classname> for the method
|
|
parameter:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class FileUploadController {
|
|
|
|
@RequestMapping(value = "/form", method = RequestMethod.POST)
|
|
public String handleFormUpload(@RequestParam("name") String name,
|
|
@RequestParam("file") Part file) {
|
|
|
|
InputStream inputStream = file.getInputStream();
|
|
<lineannotation>// store bytes from uploaded file somewhere</lineannotation>
|
|
|
|
return "redirect:uploadSuccess";
|
|
}
|
|
|
|
}</programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-multipart-forms-non-browsers">
|
|
<title>Handling a file upload request from programmatic clients</title>
|
|
|
|
<para>Multipart requests can also be submitted from non-browser clients
|
|
in a RESTful service scenario. All of the above examples and
|
|
configuration apply here as well. However, unlike browsers that
|
|
typically submit files and simple form fields, a programmatic client can
|
|
also send more complex data of a specific content type — for example a
|
|
multipart request with a file and second part with JSON formatted data:
|
|
<programlisting>POST /someUrl
|
|
Content-Type: multipart/mixed
|
|
|
|
--edt7Tfrdusa7r3lNQc79vXuhIIMlatb7PQg7Vp
|
|
Content-Disposition: form-data; name="meta-data"
|
|
Content-Type: application/json; charset=UTF-8
|
|
Content-Transfer-Encoding: 8bit
|
|
|
|
{
|
|
"name": "value"
|
|
}
|
|
--edt7Tfrdusa7r3lNQc79vXuhIIMlatb7PQg7Vp
|
|
Content-Disposition: form-data; name="file-data"; filename="file.properties"
|
|
Content-Type: text/xml
|
|
Content-Transfer-Encoding: 8bit
|
|
... File Data ...</programlisting></para>
|
|
|
|
<para>You could access the part named "meta-data" with a
|
|
<interfacename>@RequestParam("meta-data") String
|
|
metadata</interfacename> controller method argument. However, you would
|
|
probably prefer to accept a strongly typed object initialized from the
|
|
JSON formatted data in the body of the request part, very similar to the
|
|
way <interfacename>@RequestBody</interfacename> converts the body of a
|
|
non-multipart request to a target object with the help of an
|
|
<classname>HttpMessageConverter</classname>.</para>
|
|
|
|
<para>You can use the <interfacename>@RequestPart</interfacename>
|
|
annotation instead of the <interfacename>@RequestParam</interfacename>
|
|
annotation for this purpose. It allows you to have the content of a
|
|
specific multipart passed through an
|
|
<classname>HttpMessageConverter</classname> taking into consideration
|
|
the <literal>'Content-Type'</literal> header of the multipart:</para>
|
|
|
|
<programlisting language="java">@RequestMapping(value="/someUrl", method = RequestMethod.POST)
|
|
public String onSubmit(<emphasis role="bold">@RequestPart("meta-data") MetaData metadata,
|
|
@RequestPart("file-data") MultipartFile file</emphasis>) {
|
|
<lineannotation>// ...</lineannotation>
|
|
|
|
}</programlisting>
|
|
|
|
<para>Notice how <classname>MultipartFile</classname> method arguments
|
|
can be accessed with <interfacename>@RequestParam</interfacename> or
|
|
with <interfacename>@RequestPart</interfacename> interchangeably.
|
|
However, the <literal>@RequestPart("meta-data") MetaData</literal>
|
|
method argument in this case is read as JSON content based on its
|
|
<literal>'Content-Type'</literal> header and converted with the help of
|
|
the <classname>MappingJackson2HttpMessageConverter</classname>.</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-exceptionhandlers">
|
|
<title>Handling exceptions</title>
|
|
|
|
<section id="mvc-exceptionhandlers-resolver">
|
|
<title
|
|
id="mvc-HandlerExceptionResolver"><interfacename>HandlerExceptionResolver</interfacename></title>
|
|
|
|
<para>Spring <literal>HandlerExceptionResolver</literal> implementations
|
|
deal with unexpected exceptions that occur during controller execution.
|
|
A <literal>HandlerExceptionResolver</literal> somewhat resembles the
|
|
exception mappings you can define in the web application descriptor
|
|
<literal>web.xml</literal>. However, they provide a more flexible way to
|
|
do so. For example they provide information about which handler was
|
|
executing when the exception was thrown. Furthermore, a programmatic way
|
|
of handling exceptions gives you more options for responding
|
|
appropriately before the request is forwarded to another URL (the same
|
|
end result as when you use the Servlet specific exception
|
|
mappings).</para>
|
|
|
|
<para>Besides implementing the
|
|
<interfacename>HandlerExceptionResolver</interfacename> interface, which
|
|
is only a matter of implementing the
|
|
<literal>resolveException(Exception, Handler)</literal> method and
|
|
returning a <classname>ModelAndView</classname>, you may also use the
|
|
<classname>SimpleMappingExceptionResolver</classname>. This resolver
|
|
enables you to take the class name of any exception that might be thrown
|
|
and map it to a view name. This is functionally equivalent to the
|
|
exception mapping feature from the Servlet API, but it is also possible
|
|
to implement more finely grained mappings of exceptions from different
|
|
handlers.</para>
|
|
|
|
<para>By default, the <classname>DispatcherServlet</classname> registers
|
|
the <classname>DefaultHandlerExceptionResolver</classname>. This
|
|
resolver handles certain standard Spring MVC exceptions by setting a
|
|
specific response status code: <informaltable>
|
|
<tgroup cols="2">
|
|
<thead>
|
|
<row>
|
|
<entry>Exception</entry>
|
|
|
|
<entry>HTTP Status Code</entry>
|
|
</row>
|
|
</thead>
|
|
|
|
<tbody>
|
|
<row>
|
|
<entry><classname>ConversionNotSupportedException</classname></entry>
|
|
|
|
<entry>500 (Internal Server Error)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>HttpMediaTypeNotAcceptableException</classname></entry>
|
|
|
|
<entry>406 (Not Acceptable)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>HttpMediaTypeNotSupportedException</classname></entry>
|
|
|
|
<entry>415 (Unsupported Media Type)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>HttpMessageNotReadableException</classname></entry>
|
|
|
|
<entry>400 (Bad Request)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>HttpMessageNotWritableException</classname></entry>
|
|
|
|
<entry>500 (Internal Server Error)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>HttpRequestMethodNotSupportedException</classname></entry>
|
|
|
|
<entry>405 (Method Not Allowed)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>MissingServletRequestParameterException</classname></entry>
|
|
|
|
<entry>400 (Bad Request)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>NoSuchRequestHandlingMethodException</classname></entry>
|
|
|
|
<entry>404 (Not Found)</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry><classname>TypeMismatchException</classname></entry>
|
|
|
|
<entry>400 (Bad Request)</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable></para>
|
|
</section>
|
|
|
|
<section id="mvc-ann-exceptionhandler">
|
|
<title><interfacename>@ExceptionHandler</interfacename></title>
|
|
|
|
<para>An alternative to the
|
|
<interfacename>HandlerExceptionResolver</interfacename> interface is the
|
|
<interfacename>@ExceptionHandler</interfacename> annotation. You use the
|
|
<classname>@ExceptionHandler</classname> method annotation within a
|
|
controller to specify which method is invoked when an exception of a
|
|
specific type is thrown during the execution of controller methods. For
|
|
example:</para>
|
|
|
|
<programlisting language="java">@Controller
|
|
public class SimpleController {
|
|
|
|
// other controller method omitted
|
|
|
|
@ExceptionHandler(IOException.class)
|
|
public String handleIOException(IOException ex, HttpServletRequest request) {
|
|
return ClassUtils.getShortName(ex.getClass());
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>will invoke the 'handlerIOException' method when a
|
|
<classname>java.io.IOException</classname> is thrown.</para>
|
|
|
|
<para>The <classname>@ExceptionHandler</classname> value can be set to
|
|
an array of Exception types. If an exception is thrown matches one of
|
|
the types in the list, then the method annotated with the matching
|
|
<classname>@ExceptionHandler</classname> will be invoked. If the
|
|
annotation value is not set then the exception types listed as method
|
|
arguments are used.</para>
|
|
|
|
<para>Much like standard controller methods annotated with a
|
|
<classname>@RequestMapping</classname> annotation, the method arguments
|
|
and return values of <classname>@ExceptionHandler</classname> methods
|
|
are very flexible. For example, the
|
|
<classname>HttpServletRequest</classname> can be accessed in Servlet
|
|
environments and the <classname>PortletRequest</classname> in Portlet
|
|
environments. The return type can be a <classname>String</classname>,
|
|
which is interpreted as a view name or a
|
|
<classname>ModelAndView</classname> object. Refer to the API
|
|
documentation for more details.</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-coc">
|
|
<title>Convention over configuration support</title>
|
|
|
|
<para>For a lot of projects, sticking to established conventions and
|
|
having reasonable defaults is just what they (the projects) need, and
|
|
Spring Web MVC now has explicit support for <emphasis>convention over
|
|
configuration</emphasis>. What this means is that if you establish a set
|
|
of naming conventions and suchlike, you can
|
|
<emphasis>substantially</emphasis> cut down on the amount of configuration
|
|
that is required to set up handler mappings, view resolvers,
|
|
<classname>ModelAndView</classname> instances, etc. This is a great boon
|
|
with regards to rapid prototyping, and can also lend a degree of (always
|
|
good-to-have) consistency across a codebase should you choose to move
|
|
forward with it into production.</para>
|
|
|
|
<para>Convention-over-configuration support addresses the three core areas
|
|
of MVC: models, views, and controllers.</para>
|
|
|
|
<section id="mvc-coc-ccnhm">
|
|
<title>The Controller
|
|
<classname>ControllerClassNameHandlerMapping</classname></title>
|
|
|
|
<para>The <classname>ControllerClassNameHandlerMapping</classname> class
|
|
is a <interfacename>HandlerMapping</interfacename> implementation that
|
|
uses a convention to determine the mapping between request URLs and the
|
|
<interfacename>Controller</interfacename> instances that are to handle
|
|
those requests.</para>
|
|
|
|
<para>Consider the following simple
|
|
<interfacename>Controller</interfacename> implementation. Take special
|
|
notice of the <emphasis>name</emphasis> of the class.<!--Re preceding sentence, I don't see where the name of the class is discussed in explanation following the example. See my next comment.--></para>
|
|
|
|
<programlisting language="java">public class <emphasis role="bold">ViewShoppingCartController</emphasis> implements Controller {
|
|
|
|
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
|
|
<lineannotation>// the implementation is not hugely important for this example...</lineannotation>
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>Here is a snippet from the corresponding Spring Web MVC
|
|
configuration file:</para>
|
|
|
|
<programlisting language="xml"><bean class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/>
|
|
|
|
<bean id="<emphasis role="bold">viewShoppingCart</emphasis>" class="x.y.z.ViewShoppingCartController">
|
|
<lineannotation><!-- inject dependencies as required... --></lineannotation>
|
|
</bean></programlisting>
|
|
|
|
<para>The <classname>ControllerClassNameHandlerMapping</classname> finds
|
|
all of the various handler (or
|
|
<interfacename>Controller</interfacename>) beans defined in its
|
|
application context and strips <literal>Controller</literal> off the
|
|
name to define its handler mappings. Thus,
|
|
<classname>ViewShoppingCartController</classname> maps to the
|
|
<literal>/viewshoppingcart*</literal> request URL.</para>
|
|
|
|
<para>Let's look at some more examples so that the central idea becomes
|
|
immediately familiar. (Notice all lowercase in the URLs, in contrast to
|
|
camel-cased <interfacename>Controller</interfacename> class
|
|
names.)</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><classname>WelcomeController</classname> maps to the
|
|
<literal>/welcome*</literal> request URL</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>HomeController</classname> maps to the
|
|
<literal>/home*</literal> request URL</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>IndexController</classname> maps to the
|
|
<literal>/index*</literal> request URL</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>RegisterController</classname> maps to the
|
|
<literal>/register*</literal> request URL</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>In the case of <classname>MultiActionController</classname>
|
|
handler classes, the mappings generated are slightly more complex. The
|
|
<interfacename>Controller</interfacename> names in the following
|
|
examples are assumed to be <classname>MultiActionController</classname>
|
|
implementations:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><classname>AdminController</classname> maps to the
|
|
<literal>/admin/*</literal> request URL</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>CatalogController</classname> maps to the
|
|
<literal>/catalog/*</literal> request URL</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>If you follow the convention of naming your
|
|
<interfacename>Controller</interfacename> implementations as
|
|
<literal>xxx</literal><emphasis role="bold">Controller</emphasis>, the
|
|
<classname>ControllerClassNameHandlerMapping</classname> saves you the
|
|
tedium of defining and maintaining a potentially
|
|
<emphasis>looooong</emphasis>
|
|
<classname>SimpleUrlHandlerMapping</classname> (or suchlike).</para>
|
|
|
|
<para>The <classname>ControllerClassNameHandlerMapping</classname> class
|
|
extends the <classname>AbstractHandlerMapping</classname> base class so
|
|
you can define <interfacename>HandlerInterceptor</interfacename>
|
|
instances and everything else just as you would with many other
|
|
<interfacename>HandlerMapping</interfacename> implementations.</para>
|
|
</section>
|
|
|
|
<section id="mvc-coc-modelmap">
|
|
<title>The Model <classname>ModelMap</classname>
|
|
(<classname>ModelAndView</classname>)</title>
|
|
|
|
<para>The <classname>ModelMap</classname> class is essentially a
|
|
glorified <interfacename>Map</interfacename> that can make adding
|
|
objects that are to be displayed in (or on) a
|
|
<interfacename>View</interfacename> adhere to a common naming
|
|
convention. Consider the following
|
|
<interfacename>Controller</interfacename> implementation; notice that
|
|
objects are added to the <classname>ModelAndView</classname> without any
|
|
associated name specified.</para>
|
|
|
|
<programlisting language="java">public class DisplayShoppingCartController implements Controller {
|
|
|
|
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
|
|
|
|
List cartItems = <lineannotation>// get a <interfacename>List</interfacename> of <classname>CartItem</classname> objects</lineannotation>
|
|
User user = <lineannotation>// get the <classname>User</classname> doing the shopping</lineannotation>
|
|
|
|
ModelAndView mav = new ModelAndView("displayShoppingCart"); <lineannotation><-- the logical view name</lineannotation>
|
|
|
|
mav.addObject(cartItems); <lineannotation><-- look ma, no name, just the object</lineannotation>
|
|
mav.addObject(user); <lineannotation><-- and again ma!</lineannotation>
|
|
|
|
return mav;
|
|
}
|
|
}</programlisting>
|
|
|
|
<para>The <classname>ModelAndView</classname> class uses a
|
|
<classname>ModelMap</classname> class that is a custom
|
|
<interfacename>Map</interfacename> implementation that automatically
|
|
generates a key for an object when an object is added to it. The
|
|
strategy for determining the name for an added object is, in the case of
|
|
a scalar object such as <classname>User</classname>, to use the short
|
|
class name of the object's class. The following examples are names that
|
|
are generated for scalar objects put into a
|
|
<classname>ModelMap</classname> instance.</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>An <classname>x.y.User</classname> instance added will have
|
|
the name <literal>user</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An <classname>x.y.Registration</classname> instance added will
|
|
have the name <literal>registration</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An <classname>x.y.Foo</classname> instance added will have the
|
|
name <literal>foo</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>java.util.HashMap</classname> instance added will
|
|
have the name <literal>hashMap</literal> generated. You probably
|
|
want to be explicit about the name in this case because
|
|
<literal>hashMap</literal> is less than intuitive.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Adding <literal>null</literal> will result in an
|
|
<classname>IllegalArgumentException</classname> being thrown. If the
|
|
object (or objects) that you are adding could be
|
|
<literal>null</literal>, then you will also want to be explicit
|
|
about the name.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<sidebar>
|
|
<title>What, no automatic pluralization?</title>
|
|
|
|
<para>Spring Web MVC's convention-over-configuration support does not
|
|
support automatic pluralization. That is, you cannot add a
|
|
<interfacename>List</interfacename> of <classname>Person</classname>
|
|
objects to a <classname>ModelAndView</classname> and have the
|
|
generated name be <classname>people</classname>.</para>
|
|
|
|
<para>This decision was made after some debate, with the
|
|
<quote>Principle of Least Surprise</quote> winning out in the
|
|
end.</para>
|
|
</sidebar>
|
|
|
|
<para>The strategy for generating a name after adding a
|
|
<interfacename>Set</interfacename> or a
|
|
<interfacename>List</interfacename> is to peek into the collection, take
|
|
the short class name of the first object in the collection, and use that
|
|
with <literal>List</literal> appended to the name. The same applies to
|
|
arrays although with arrays it is not necessary to peek into the array
|
|
contents. A few examples will make the semantics of name generation for
|
|
collections clearer:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>An <classname>x.y.User[]</classname> array with zero or more
|
|
<classname>x.y.User</classname> elements added will have the name
|
|
<literal>userList</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An <classname>x.y.Foo[]</classname> array with zero or more
|
|
<classname>x.y.User</classname> elements added will have the name
|
|
<literal>fooList</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>java.util.ArrayList</classname> with one or more
|
|
<classname>x.y.User</classname> elements added will have the name
|
|
<literal>userList</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>A <classname>java.util.HashSet</classname> with one or more
|
|
<classname>x.y.Foo</classname> elements added will have the name
|
|
<literal>fooList</literal> generated.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>An <emphasis role="bold">empty</emphasis>
|
|
<classname>java.util.ArrayList</classname> will not be added at all
|
|
(in effect, the <methodname>addObject(..)</methodname> call will
|
|
essentially be a no-op).</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</section>
|
|
|
|
<section id="mvc-coc-r2vnt">
|
|
<title>The View -
|
|
<interfacename>RequestToViewNameTranslator</interfacename></title>
|
|
|
|
<para>The <interfacename>RequestToViewNameTranslator</interfacename>
|
|
interface determines a logical <interfacename>View</interfacename> name
|
|
when no such logical view name is explicitly supplied. It has just one
|
|
implementation, the
|
|
<classname>DefaultRequestToViewNameTranslator</classname> class.</para>
|
|
|
|
<para>The <classname>DefaultRequestToViewNameTranslator</classname> maps
|
|
request URLs to logical view names, as with this example:</para>
|
|
|
|
<programlisting language="java">public class RegistrationController implements Controller {
|
|
|
|
public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
|
|
<lineannotation>// process the request...</lineannotation>
|
|
ModelAndView mav = new ModelAndView();
|
|
<lineannotation>// add <emphasis role="bold">data</emphasis> as necessary to the model...</lineannotation>
|
|
return mav;
|
|
<lineannotation>// notice that no <interfacename>View</interfacename> or logical view name has been set</lineannotation>
|
|
}
|
|
}</programlisting>
|
|
|
|
<programlisting language="xml"><?xml version="1.0" encoding="UTF-8"?>
|
|
<beans xmlns="http://www.springframework.org/schema/beans"
|
|
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
|
xsi:schemaLocation="
|
|
http://www.springframework.org/schema/beans
|
|
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
|
|
|
|
<lineannotation><!-- this bean with the well known name generates view names for us --></lineannotation>
|
|
<bean id="viewNameTranslator"
|
|
class="org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator"/>
|
|
|
|
<bean class="x.y.RegistrationController">
|
|
<lineannotation><!-- inject dependencies as necessary --></lineannotation>
|
|
</bean>
|
|
|
|
<lineannotation><!-- maps request URLs to Controller names --></lineannotation>
|
|
<bean class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/>
|
|
|
|
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
|
|
<property name="prefix" value="/WEB-INF/jsp/"/>
|
|
<property name="suffix" value=".jsp"/>
|
|
</bean>
|
|
|
|
</beans></programlisting>
|
|
|
|
<para>Notice how in the implementation of the
|
|
<literal>handleRequest(..)</literal> method no
|
|
<interfacename>View</interfacename> or logical view name is ever set on
|
|
the <classname>ModelAndView</classname> that is returned. The
|
|
<classname>DefaultRequestToViewNameTranslator</classname> is tasked with
|
|
generating a <emphasis>logical view name</emphasis> from the URL of the
|
|
request. In the case of the above
|
|
<classname>RegistrationController</classname>, which is used in
|
|
conjunction with the
|
|
<classname>ControllerClassNameHandlerMapping</classname>, a request URL
|
|
of <literal>http://localhost/registration.html</literal> results in a
|
|
logical view name of <literal>registration</literal> being generated by
|
|
the <classname>DefaultRequestToViewNameTranslator</classname>. This
|
|
logical view name is then resolved into the
|
|
<literal>/WEB-INF/jsp/registration.jsp</literal> view by the
|
|
<classname>InternalResourceViewResolver</classname> bean.</para>
|
|
|
|
<tip>
|
|
<para>You do not need to define a
|
|
<classname>DefaultRequestToViewNameTranslator</classname> bean
|
|
explicitly. If you like the default settings of the
|
|
<classname>DefaultRequestToViewNameTranslator</classname>, you can
|
|
rely on the Spring Web MVC <classname>DispatcherServlet</classname> to
|
|
instantiate an instance of this class if one is not explicitly
|
|
configured.</para>
|
|
</tip>
|
|
|
|
<para>Of course, if you need to change the default settings, then you do
|
|
need to configure your own
|
|
<classname>DefaultRequestToViewNameTranslator</classname> bean
|
|
explicitly. Consult the comprehensive Javadoc for the
|
|
<classname>DefaultRequestToViewNameTranslator</classname> class for
|
|
details of the various properties that can be configured.</para>
|
|
</section>
|
|
</section>
|
|
|
|
<section id="mvc-etag">
|
|
<title>ETag support</title>
|
|
|
|
<para>An <ulink url="http://en.wikipedia.org/wiki/HTTP_ETag">ETag</ulink>
|
|
(entity tag) is an HTTP response header returned by an HTTP/1.1 compliant
|
|
web server used to determine change in content at a given URL. It can be
|
|
considered to be the more sophisticated successor to the
|
|
<literal>Last-Modified</literal> header. When a server returns a
|
|
representation with an ETag header, the client can use this header in
|
|
subsequent GETs, in an <literal>If-None-Match</literal> header. If the
|
|
content has not changed, the server returns <literal>304: Not
|
|
Modified</literal>.</para>
|
|
|
|
<para>Support for ETags is provided by the Servlet filter
|
|
<classname>ShallowEtagHeaderFilter</classname>. It is a plain Servlet
|
|
Filter, and thus can be used in combination with any web framework. <!--The preceding sentence was a fragment, not a complete sentence. Have I reworded ok?-->The
|
|
<classname>ShallowEtagHeaderFilter</classname> filter creates so-called
|
|
shallow ETags (as opposed to deep ETags, more about that later).<!--Provide xref to deep ETags.-->The
|
|
filter caches the content of the rendered JSP (or other content),
|
|
generates an MD5 hash over that, and returns that as an ETag header in the
|
|
response. The next time a client sends a request for the same resource, it
|
|
uses that hash as the <literal>If-None-Match</literal> value. The filter
|
|
detects this, renders the view again, and compares the two hashes. If they
|
|
are equal, a <literal>304</literal> is returned. This filter will not save
|
|
processing power, as the view is still rendered. The only thing it saves
|
|
is bandwidth, as the rendered response is not sent back over the
|
|
wire.</para>
|
|
|
|
<para>You configure the <classname>ShallowEtagHeaderFilter</classname> in
|
|
<filename>web.xml</filename>:</para>
|
|
|
|
<programlisting language="xml"><filter>
|
|
<filter-name>etagFilter</filter-name>
|
|
<filter-class>org.springframework.web.filter.ShallowEtagHeaderFilter</filter-class>
|
|
</filter>
|
|
|
|
<filter-mapping>
|
|
<filter-name>etagFilter</filter-name>
|
|
<servlet-name>petclinic</servlet-name>
|
|
</filter-mapping></programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-config">
|
|
<title>Configuring Spring MVC</title>
|
|
|
|
<para><xref linkend="mvc-servlet-special-bean-types"/> and
|
|
<xref linkend="mvc-servlet-config"/> explained about
|
|
Spring MVC's special beans and the default implementations
|
|
used by the <classname>DispatcherServlet</classname>.
|
|
In this section you'll learn about two additional ways of
|
|
configuring Spring MVC. Namely the MVC Java config and
|
|
the MVC XML namespace.
|
|
</para>
|
|
|
|
<para>The MVC Java config and the MVC namespace provide
|
|
similar default configuration that overrides
|
|
the <classname>DispatcherServlet</classname> defaults.
|
|
The goal is to spare most applications from having to
|
|
having to create the same configuration and also to
|
|
provide higher-level constructs for configuring
|
|
Spring MVC that serve as a simple starting point and
|
|
require little or no prior knowledge of the underlying
|
|
configuration.</para>
|
|
|
|
<para>You can choose either the MVC Java config or the
|
|
MVC namespace depending on your preference. Also as you
|
|
will see further below, with the MVC Java config it is
|
|
easier to see the underlying configuration as well as
|
|
to make fine-grained customizations directly to the
|
|
created Spring MVC beans.
|
|
But let's start from the beginning.
|
|
</para>
|
|
|
|
<section id="mvc-config-enable">
|
|
<title>Enabling MVC Java Config or the MVC XML Namespace</title>
|
|
|
|
<para>To enable MVC Java config add the annotation
|
|
<interfacename>@EnableWebMvc</interfacename> to one of your
|
|
<interfacename>@Configuration</interfacename> classes:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
public class WebConfig {
|
|
|
|
}</programlisting>
|
|
|
|
<para>To achieve the same in XML use the <literal>mvc:annotation-driven</literal> element:</para>
|
|
|
|
<programlisting language="xml"><?xml version="1.0" encoding="UTF-8"?>
|
|
<beans xmlns="http://www.springframework.org/schema/beans"
|
|
xmlns:mvc="http://www.springframework.org/schema/mvc"
|
|
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
|
|
xsi:schemaLocation="
|
|
http://www.springframework.org/schema/beans
|
|
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
|
|
http://www.springframework.org/schema/mvc
|
|
http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd">
|
|
|
|
<mvc:annotation-driven />
|
|
|
|
<beans></programlisting>
|
|
|
|
<para>The above registers a
|
|
<classname>RequestMappingHandlerMapping</classname>, a
|
|
<classname>RequestMappingHandlerAdapter</classname>, and an
|
|
<classname>ExceptionHandlerExceptionResolver</classname> (among others)
|
|
in support of processing requests with annotated controller methods using
|
|
annotations such as <interfacename>@RequestMapping </interfacename>,
|
|
<interfacename>@ExceptionHandler</interfacename>, and others.</para>
|
|
|
|
<para>It also enables the following:
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>Spring 3 style type conversion through a <link
|
|
linkend="core-convert">ConversionService</link> instance
|
|
in addition to the JavaBeans PropertyEditors used for Data Binding.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Support for <link linkend="format">formatting</link> Number
|
|
fields using the <interfacename>@NumberFormat</interfacename>
|
|
annotation through the
|
|
<interfacename>ConversionService</interfacename>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Support for <link linkend="format">formatting</link> Date,
|
|
Calendar, Long, and Joda Time fields using the
|
|
<interfacename>@DateTimeFormat</interfacename>
|
|
annotation, if Joda Time 1.3 or higher is present on the
|
|
classpath.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Support for <link
|
|
linkend="validation-mvc-jsr303">validating</link> @Controller
|
|
inputs with <interfacename>@Valid</interfacename>,
|
|
if a JSR-303 Provider is present on the classpath.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>HttpMessageConverter support for
|
|
<interfacename>@RequestBody</interfacename> method
|
|
parameters and <interfacename>@ResponseBody</interfacename>
|
|
method return values from
|
|
<interfacename>@RequestMapping</interfacename> or
|
|
<interfacename>@ExceptionHandler</interfacename> methods.</para>
|
|
|
|
<para>This is the complete list of HttpMessageConverters set up by
|
|
mvc:annotation-driven: <itemizedlist>
|
|
<listitem>
|
|
<para><classname>ByteArrayHttpMessageConverter</classname>
|
|
converts byte arrays.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>StringHttpMessageConverter</classname>
|
|
converts strings.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>ResourceHttpMessageConverter</classname>
|
|
converts to/from
|
|
<classname>org.springframework.core.io.Resource</classname>
|
|
for all media types.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>SourceHttpMessageConverter</classname>
|
|
converts to/from a
|
|
<classname>javax.xml.transform.Source</classname>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>FormHttpMessageConverter</classname>
|
|
converts form data to/from a
|
|
<classname>MultiValueMap<String,
|
|
String></classname>.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>Jaxb2RootElementHttpMessageConverter</classname>
|
|
converts Java objects to/from XML — added if JAXB2 is
|
|
present on the classpath.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>MappingJackson2HttpMessageConverter</classname>
|
|
(or <classname>MappingJacksonHttpMessageConverter</classname>)
|
|
converts to/from JSON — added if Jackson 2 (or Jackson) is present
|
|
on the classpath.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>AtomFeedHttpMessageConverter</classname>
|
|
converts Atom feeds — added if Rome is present on the
|
|
classpath.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><classname>RssChannelHttpMessageConverter</classname>
|
|
converts RSS feeds — added if Rome is present on the
|
|
classpath.</para>
|
|
</listitem>
|
|
</itemizedlist></para>
|
|
|
|
</listitem>
|
|
</orderedlist>
|
|
</para>
|
|
</section>
|
|
|
|
<section id="mvc-config-customize">
|
|
<title>Customizing the Provided Configuration</title>
|
|
|
|
<para>To customize the default configuration in Java you simply
|
|
implement the <interfacename>WebMvcConfigurer</interfacename>
|
|
interface or more likely extend the class
|
|
<classname>WebMvcConfigurerAdapter</classname> and override
|
|
the methods you need. Below is an example of some of the available
|
|
methods to override. See <interfacename>WebMvcConifgurer</interfacename> for
|
|
a list of all methods and the Javadoc for further details:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
public class WebConfig extends WebMvcConfigurerAdapter {
|
|
|
|
@Override
|
|
protected void addFormatters(FormatterRegistry registry) {
|
|
// Add formatters and/or converters
|
|
}
|
|
|
|
@Override
|
|
public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
|
|
// Configure the list of HttpMessageConverters to use
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>To customize the default configuration of
|
|
<literal><mvc:annotation-driven /></literal> check what
|
|
attributes and sub-elements it supports. You can view the
|
|
<ulink url="http://static.springsource.org/schema/mvc/spring-mvc-3.1.xsd">Spring MVC XML schema</ulink>
|
|
or use the code completion feature of your IDE to discover
|
|
what attributes and sub-elements are available.
|
|
The sample below shows a subset of what is available:</para>
|
|
|
|
<programlisting language="xml"><mvc:annotation-driven conversion-service="conversionService">
|
|
<mvc:message-converters>
|
|
<bean class="org.example.MyHttpMessageConverter"/>
|
|
<bean class="org.example.MyOtherHttpMessageConverter"/>
|
|
</mvc:message-converters>
|
|
</mvc:annotation-driven>
|
|
|
|
<bean id="conversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean">
|
|
<property name="formatters">
|
|
<list>
|
|
<bean class="org.example.MyFormatter"/>
|
|
<bean class="org.example.MyOtherFormatter"/>
|
|
</list>
|
|
</property>
|
|
</bean></programlisting>
|
|
|
|
</section>
|
|
|
|
<section id="mvc-config-interceptors">
|
|
<title>Configuring Interceptors</title>
|
|
|
|
<para>You can configure <interfacename>HandlerInterceptors</interfacename>
|
|
or <interfacename>WebRequestInterceptors</interfacename> to be applied
|
|
to all incoming requests or restricted to specific URL path patterns.</para>
|
|
|
|
<para>An example of registering interceptors in Java:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
public class WebConfig extends WebMvcConfigurerAdapter {
|
|
|
|
@Override
|
|
public void addInterceptors(InterceptorRegistry registry) {
|
|
registry.addInterceptor(new LocalInterceptor());
|
|
registry.addInterceptor(new SecurityInterceptor()).addPathPatterns("/secure/*");
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>And in XML use the <literal><mvc:interceptors></literal> element:</para>
|
|
|
|
<programlisting language="xml"><mvc:interceptors>
|
|
<bean class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor" />
|
|
<mvc:interceptor>
|
|
<mapping path="/secure/*"/>
|
|
<bean class="org.example.SecurityInterceptor" />
|
|
</mvc:interceptor>
|
|
</mvc:interceptors>
|
|
</programlisting>
|
|
|
|
</section>
|
|
|
|
<section id="mvc-config-view-controller">
|
|
<title>Configuring View Controllers</title>
|
|
|
|
<para>This is a shortcut for defining a
|
|
<classname>ParameterizableViewController</classname> that immediately
|
|
forwards to a view when invoked. Use it in static cases when there is no
|
|
Java controller logic to execute before the view generates the
|
|
response.</para>
|
|
|
|
<para>An example of forwarding a request for <literal>"/"</literal>
|
|
to a view called <literal>"home"</literal> in Java:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
public class WebConfig extends WebMvcConfigurerAdapter {
|
|
|
|
@Override
|
|
public void addViewControllers(ViewControllerRegistry registry) {
|
|
registry.addViewController("/").setViewName("home");
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>And the same in XML use the <literal><mvc:view-controller></literal> element:</para>
|
|
|
|
<programlisting language="xml"><mvc:view-controller path="/" view-name="home"/></programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-config-static-resources">
|
|
<title>Configuring Serving of Resources</title>
|
|
|
|
<para>This option allows static resource requests following a particular
|
|
URL pattern to be served by a
|
|
<classname>ResourceHttpRequestHandler</classname> from any of a list of
|
|
<classname>Resource</classname> locations. This provides a convenient
|
|
way to serve static resources from locations other than the web
|
|
application root, including locations on the classpath. The
|
|
<code>cache-period</code> property may be used to set far future
|
|
expiration headers (1 year is the recommendation of optimization tools
|
|
such as Page Speed and YSlow) so that they will be more efficiently
|
|
utilized by the client. The handler also properly evaluates the
|
|
<code>Last-Modified</code> header (if present) so that a
|
|
<code>304</code> status code will be returned as appropriate, avoiding
|
|
unnecessary overhead for resources that are already cached by the
|
|
client. For example, to serve resource requests with a URL pattern of
|
|
<code>/resources/**</code> from a <code>public-resources</code>
|
|
directory within the web application root you would use:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
public class WebConfig extends WebMvcConfigurerAdapter {
|
|
|
|
@Override
|
|
public void addResourceHandlers(ResourceHandlerRegistry registry) {
|
|
registry.addResourceHandler("/resources/**").addResourceLocations("/public-resources/");
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>And the same in XML:</para>
|
|
|
|
<programlisting language="xml"><mvc:resources mapping="/resources/**" location="/public-resources/"/></programlisting>
|
|
|
|
<para>To serve these resources with a 1-year future expiration to ensure
|
|
maximum use of the browser cache and a reduction in HTTP requests made
|
|
by the browser:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
public class WebConfig extends WebMvcConfigurerAdapter {
|
|
|
|
@Override
|
|
public void addResourceHandlers(ResourceHandlerRegistry registry) {
|
|
registry.addResourceHandler("/resources/**").addResourceLocations("/public-resources/").setCachePeriod(31556926);
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>And in XML:</para>
|
|
|
|
<programlisting language="xml"><mvc:resources mapping="/resources/**" location="/public-resources/" cache-period="31556926"/></programlisting>
|
|
|
|
<para>The <code>mapping</code> attribute must be an Ant pattern that can
|
|
be used by <classname>SimpleUrlHandlerMapping</classname>, and the
|
|
<code>location</code> attribute must specify one or more valid resource
|
|
directory locations. Multiple resource locations may be specified using
|
|
a comma-separated list of values. The locations specified will be
|
|
checked in the specified order for the presence of the resource for any
|
|
given request. For example, to enable the serving of resources from both
|
|
the web application root and from a known path of
|
|
<code>/META-INF/public-web-resources/</code> in any jar on the
|
|
classpath use:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
public class WebConfig extends WebMvcConfigurerAdapter {
|
|
|
|
@Override
|
|
public void addResourceHandlers(ResourceHandlerRegistry registry) {
|
|
registry.addResourceHandler("/resources/**")
|
|
.addResourceLocations("/", "classpath:/META-INF/public-web-resources/");
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>And in XML:</para>
|
|
|
|
<programlisting language="xml"><mvc:resources mapping="/resources/**" location="/, classpath:/META-INF/public-web-resources/"/></programlisting>
|
|
|
|
<para>When serving resources that may change when a new version of the
|
|
application is deployed, it is recommended that you incorporate a
|
|
version string into the mapping pattern used to request the resources,
|
|
so that you may force clients to request the newly deployed version of
|
|
your application's resources. Such a version string can be parameterized
|
|
and accessed using SpEL so that it may be easily managed in a single
|
|
place when deploying new versions.</para>
|
|
|
|
<para>As an example, let's consider an application that uses a
|
|
performance-optimized custom build (as recommended) of the Dojo
|
|
JavaScript library in production, and that the build is generally
|
|
deployed within the web application at a path of
|
|
<code>/public-resources/dojo/dojo.js</code>. Since different parts of
|
|
Dojo may be incorporated into the custom build for each new version of
|
|
the application, the client web browsers need to be forced to
|
|
re-download that custom-built <code>dojo.js</code> resource any time a
|
|
new version of the application is deployed. A simple way to achieve this
|
|
would be to manage the version of the application in a properties file,
|
|
such as:</para>
|
|
|
|
<programlisting>application.version=1.0.0</programlisting>
|
|
|
|
<para>and then to make the properties file's values accessible to SpEL
|
|
as a bean using the <code>util:properties</code> tag:</para>
|
|
|
|
<programlisting language="xml"><util:properties id="applicationProps" location="/WEB-INF/spring/application.properties"/></programlisting>
|
|
|
|
<para>With the application version now accessible via SpEL, we can
|
|
incorporate this into the use of the <code>resources</code> tag:</para>
|
|
|
|
<programlisting language="xml"><mvc:resources mapping="/resources-#{applicationProps['application.version']}/**" location="/public-resources/"/></programlisting>
|
|
|
|
<para>In Java, you can use the <interfacename>@PropertySouce</interfacename>
|
|
annotation and then inject the <classname>Environment</classname>
|
|
abstraction for access to all defined properties:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
@PropertySource("/WEB-INF/spring/application.properties")
|
|
public class WebConfig extends WebMvcConfigurerAdapter {
|
|
|
|
@Inject Environment env;
|
|
|
|
@Override
|
|
public void addResourceHandlers(ResourceHandlerRegistry registry) {
|
|
registry.addResourceHandler("/resources-" + env.getProperty("application.version") + "/**")
|
|
.addResourceLocations("/public-resources/");
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>and finally, to request the resource with the proper URL, we can
|
|
take advantage of the Spring JSP tags:</para>
|
|
|
|
<programlisting language="xml"><spring:eval expression="@applicationProps['application.version']" var="applicationVersion"/>
|
|
|
|
<spring:url value="/resources-{applicationVersion}" var="resourceUrl">
|
|
<spring:param name="applicationVersion" value="${applicationVersion}"/>
|
|
</spring:url>
|
|
|
|
<script src="${resourceUrl}/dojo/dojo.js" type="text/javascript"> </script></programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-default-servlet-handler">
|
|
<title>mvc:default-servlet-handler</title>
|
|
|
|
<para>This tag allows for mapping the <code>DispatcherServlet</code> to
|
|
"/" (thus overriding the mapping of the container's default Servlet),
|
|
while still allowing static resource requests to be handled by the
|
|
container's default Servlet. It configures a
|
|
<code>DefaultServletHttpRequestHandler</code> with a URL mapping of
|
|
"/**" and the lowest priority relative to other URL mappings.</para>
|
|
|
|
<para>This handler will forward all requests to the default Servlet.
|
|
Therefore it is important that it remains last in the order of all other
|
|
URL <code>HandlerMappings</code>. That will be the case if you use
|
|
<code><mvc:annotation-driven></code> or alternatively if you are
|
|
setting up your own customized <code>HandlerMapping</code> instance be
|
|
sure to set its <code>order</code> property to a value lower than that
|
|
of the <code>DefaultServletHttpRequestHandler</code>, which is
|
|
<code>Integer.MAX_VALUE</code>.</para>
|
|
|
|
<para>To enable the feature using the default setup use:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
public class WebConfig extends WebMvcConfigurerAdapter {
|
|
|
|
@Override
|
|
public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
|
|
configurer.enable();
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>Or in XML:</para>
|
|
|
|
<programlisting language="xml"><mvc:default-servlet-handler/></programlisting>
|
|
|
|
<para>The caveat to overriding the "/" Servlet mapping is that the
|
|
<code>RequestDispatcher</code> for the default Servlet must be retrieved
|
|
by name rather than by path. The
|
|
<code>DefaultServletHttpRequestHandler</code> will attempt to
|
|
auto-detect the default Servlet for the container at startup time, using
|
|
a list of known names for most of the major Servlet containers
|
|
(including Tomcat, Jetty, GlassFish, JBoss, Resin, WebLogic, and
|
|
WebSphere). If the default Servlet has been custom configured with a
|
|
different name, or if a different Servlet container is being used where
|
|
the default Servlet name is unknown, then the default Servlet's name
|
|
must be explicitly provided as in the following example:</para>
|
|
|
|
<programlisting language="java">@EnableWebMvc
|
|
@Configuration
|
|
public class WebConfig extends WebMvcConfigurerAdapter {
|
|
|
|
@Override
|
|
public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
|
|
configurer.enable("myCustomDefaultServlet");
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>Or in XML:</para>
|
|
|
|
<programlisting language="xml"><mvc:default-servlet-handler default-servlet-name="myCustomDefaultServlet"/></programlisting>
|
|
</section>
|
|
|
|
<section id="mvc-resources">
|
|
<title>More Spring Web MVC Resources</title>
|
|
|
|
<para>See the following links and pointers for more resources about Spring Web MVC:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>There are many excellent articles and tutorials that show how to
|
|
build web applications with Spring MVC. Read them at the <ulink
|
|
url="http://www.springsource.org/documentation">Spring
|
|
Documentation</ulink> page.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para><quote>Expert Spring Web MVC and Web Flow</quote> by Seth Ladd
|
|
and others (published by Apress) is an excellent hard copy source of
|
|
Spring Web MVC goodness.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</section>
|
|
|
|
<section id="mvc-config-advanced-java">
|
|
<title>Advanced Customizations with MVC Java Config</title>
|
|
|
|
<para>As you can see from the above examples, MVC Java config and
|
|
the MVC namespace provide higher level constructs that do not
|
|
require deep knowledge of the underlying beans created for you.
|
|
Instead it helps you to focus on your application needs.
|
|
However, at some point you may need more fine-grained control
|
|
or you may simply wish to understand the underlying configuration.</para>
|
|
|
|
<para>The first step towards more fine-grained control is to see the
|
|
underlying beans created for you. In MVC Java config you can
|
|
see the Javadoc and the <interfacename>@Bean</interfacename>
|
|
methods in <classname>WebMvcConfigurationSupport</classname>.
|
|
The configuration in this class is automatically imported
|
|
through the <interfacename>@EnableWebMvc</interfacename> annotation.
|
|
In fact if you open <interfacename>@EnableWebMvc</interfacename> you can
|
|
see the <interfacename>@Import</interfacename> statement.</para>
|
|
|
|
<para>The next step towards more fine-grained control is to
|
|
customize a property on one of the beans created in
|
|
<classname>WebMvcConfigurationSupport</classname> or perhaps
|
|
to provide your own instance. This requires two things --
|
|
remove the <interfacename>@EnableWebMvc</interfacename>
|
|
annotation in order to prevent the import and then
|
|
extend directly from <classname>WebMvcConfigurationSupport</classname>.
|
|
Here is an example:
|
|
</para>
|
|
|
|
<programlisting language="java">@Configuration
|
|
public class WebConfig extends WebMvcConfigurationSupport {
|
|
|
|
@Override
|
|
public void addInterceptors(InterceptorRegistry registry){
|
|
// ...
|
|
}
|
|
|
|
@Override
|
|
@Bean
|
|
public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
|
|
|
|
// Create or let "super" create the adapter
|
|
// Then customize one of its properties
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>Note that modifying beans in this way does not prevent
|
|
you from using any of the higher-level constructs shown earlier in
|
|
this section. </para>
|
|
|
|
</section>
|
|
|
|
<section id="mvc-config-advanced-xml">
|
|
<title>Advanced Customizations with the MVC Namespace</title>
|
|
|
|
<para>Fine-grained control over the configuration created for
|
|
you is a bit harder with the MVC namespace.</para>
|
|
|
|
<para>If you do need to do that, rather than replicating the
|
|
configuration it provides, consider configuring a
|
|
<interfacename>BeanPostProcessor</interfacename> that detects
|
|
the bean you want to customize by type and then modifying its
|
|
properties as necessary. For example:</para>
|
|
|
|
<programlisting language="java">@Component
|
|
public class MyPostProcessor implements BeanPostProcessor {
|
|
|
|
public Object postProcessBeforeInitialization(Object bean, String name) throws BeansException {
|
|
if (bean instanceof RequestMappingHandlerAdapter) {
|
|
// Modify properties of the adapter
|
|
}
|
|
}
|
|
|
|
}</programlisting>
|
|
|
|
<para>Note that <classname>MyPostProcessor</classname> needs to be
|
|
included in an <interfacename><component scan /></interfacename>
|
|
in order for it to be detected or if you prefer you can declare it
|
|
explicitly with an XML bean declaration.</para>
|
|
</section>
|
|
|
|
</section>
|
|
|
|
</chapter>
|