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Add reference docs tasks to Gradle build

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- Move spring-webflow-reference to src/reference
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Rossen Stoyanchev
2012-05-24 18:57:30 -04:00
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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="actions">
<title>Executing actions</title>
<sect1 id="actions-introduction">
<title>Introduction</title>
<para>
This chapter shows you how to use the <code>action-state</code> element to control the execution of an action at a point within a flow.
It will also show how to use the <code>decision-state</code> element to make a flow routing decision.
Finally, several examples of invoking actions from the various points possible within a flow will be discussed.
</para>
</sect1>
<sect1 id="action-state">
<title>Defining action states</title>
<para>
Use the <code>action-state</code> element when you wish to invoke an action, then transition to another state based on the action's outcome:
</para>
<programlisting language="xml"><![CDATA[
<action-state id="moreAnswersNeeded">
<evaluate expression="interview.moreAnswersNeeded()" />
<transition on="yes" to="answerQuestions" />
<transition on="no" to="finish" />
</action-state>]]>
</programlisting>
<para>
The full example below illustrates a interview flow that uses the action-state above to determine if more answers are needed to complete the interview:
</para>
<programlisting language="xml"><![CDATA[
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
<on-start>
<evaluate expression="interviewFactory.createInterview()" result="flowScope.interview" />
</on-start>
<view-state id="answerQuestions" model="questionSet">
<on-entry>
<evaluate expression="interview.getNextQuestionSet()" result="viewScope.questionSet" />
</on-entry>
<transition on="submitAnswers" to="moreAnswersNeeded">
<evaluate expression="interview.recordAnswers(questionSet)" />
</transition>
</view-state>
<action-state id="moreAnswersNeeded">
<evaluate expression="interview.moreAnswersNeeded()" />
<transition on="yes" to="answerQuestions" />
<transition on="no" to="finish" />
</action-state>
<end-state id="finish" />
</flow>]]>
</programlisting>
</sect1>
<sect1 id="decision-state">
<title>Defining decision states</title>
<para>
Use the <code>decision-state</code> element as an alternative to the action-state to make a routing decision using a convenient if/else syntax.
The example below shows the <code>moreAnswersNeeded</code> state above now implemented as a decision state instead of an action-state:
</para>
<programlisting language="xml"><![CDATA[
<decision-state id="moreAnswersNeeded">
<if test="interview.moreAnswersNeeded()" then="answerQuestions" else="finish" />
</decision-state>]]>
</programlisting>
</sect1>
<sect1 id="action-outcome-events">
<title>Action outcome event mappings</title>
<para>
Actions often invoke methods on plain Java objects.
When called from action-states and decision-states, these method return values can be used to drive state transitions.
Since transitions are triggered by events, a method return value must first be mapped to an Event object.
The following table describes how common return value types are mapped to Event objects:
</para>
<table id="event-mapping-table">
<title>Action method return value to event id mappings</title>
<tgroup cols="2">
<colspec colname="Method return type" colwidth="*"/>
<colspec colname="Event identifier" colwidth="3*"/>
<thead>
<row>
<entry>Method return type</entry>
<entry>Mapped Event identifier expression</entry>
</row>
</thead>
<tbody>
<row>
<entry>java.lang.String</entry>
<entry>the String value</entry>
</row>
<row>
<entry>java.lang.Boolean</entry>
<entry>yes (for true), no (for false)</entry>
</row>
<row>
<entry>java.lang.Enum</entry>
<entry>the Enum name</entry>
</row>
<row>
<entry>any other type</entry>
<entry>success</entry>
</row>
</tbody>
</tgroup>
</table>
<para>
This is illustrated in the example action state below, which invokes a method that returns a boolean value:
</para>
<programlisting language="xml"><![CDATA[
<action-state id="moreAnswersNeeded">
<evaluate expression="interview.moreAnswersNeeded()" />
<transition on="yes" to="answerQuestions" />
<transition on="no" to="finish" />
</action-state>]]>
</programlisting>
</sect1>
<sect1 id="action-implementations">
<title>Action implementations</title>
<para>
While writing action code as POJO logic is the most common, there are several other action implementation options.
Sometimes you need to write action code that needs access to the flow context.
You can always invoke a POJO and pass it the flowRequestContext as an EL variable.
Alternatively, you may implement the <code>Action</code> interface or extend from the <code>MultiAction</code> base class.
These options provide stronger type safety when you have a natural coupling between your action code and Spring Web Flow APIs.
Examples of each of these approaches are shown below.
</para>
<sect2>
<title>Invoking a POJO action</title>
<programlisting language="xml"><![CDATA[
<evaluate expression="pojoAction.method(flowRequestContext)" />]]>
</programlisting>
<programlisting language="java"><![CDATA[
public class PojoAction {
public String method(RequestContext context) {
...
}
}]]>
</programlisting>
</sect2>
<sect2>
<title>Invoking a custom Action implementation</title>
<programlisting language="xml"><![CDATA[
<evaluate expression="customAction" />]]>
</programlisting>
<programlisting language="java"><![CDATA[
public class CustomAction implements Action {
public Event execute(RequestContext context) {
...
}
}]]>
</programlisting>
</sect2>
<sect2>
<title>Invoking a MultiAction implementation</title>
<programlisting language="xml"><![CDATA[
<evaluate expression="multiAction.actionMethod1" />
]]>
</programlisting>
<programlisting language="java"><![CDATA[
public class CustomMultiAction extends MultiAction {
public Event actionMethod1(RequestContext context) {
...
}
public Event actionMethod2(RequestContext context) {
...
}
...
}]]>
</programlisting>
</sect2>
</sect1>
<sect1 id="action-exceptions">
<title>Action exceptions</title>
<para>
Actions often invoke services that encapsulate complex business logic.
These services may throw business exceptions that the action code should handle.
</para>
<sect2>
<title>Handling a business exception with a POJO action</title>
<para>
The following example invokes an action that catches a business exception, adds a error message to the context, and returns a result event identifier.
The result is treated as a flow event which the calling flow can then respond to.
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="bookingAction.makeBooking(booking, flowRequestContext)" />]]>
</programlisting>
<programlisting language="java"><![CDATA[
public class BookingAction {
public String makeBooking(Booking booking, RequestContext context) {
try {
BookingConfirmation confirmation = bookingService.make(booking);
context.getFlowScope().put("confirmation", confirmation);
return "success";
} catch (RoomNotAvailableException e) {
context.addMessage(new MessageBuilder().error().
.defaultText("No room is available at this hotel").build());
return "error";
}
}
}]]>
</programlisting>
</sect2>
<sect2>
<title>Handling a business exception with a MultiAction</title>
<para>
The following example is functionally equivlant to the last, but implemented as a MultiAction instead of a POJO action.
The MultiAction requires its action methods to be of the signature <code>Event ${methodName}(RequestContext)</code>, providing stronger type safety, while a POJO action allows for more freedom.
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="bookingAction.makeBooking" />]]>
</programlisting>
<programlisting language="java"><![CDATA[
public class BookingAction extends MultiAction {
public Event makeBooking(RequestContext context) {
try {
Booking booking = (Booking) context.getFlowScope().get("booking");
BookingConfirmation confirmation = bookingService.make(booking);
context.getFlowScope().put("confirmation", confirmation);
return success();
} catch (RoomNotAvailableException e) {
context.getMessageContext().addMessage(new MessageBuilder().error().
.defaultText("No room is available at this hotel").build());
return error();
}
}
}]]>
</programlisting>
</sect2>
</sect1>
<sect1 id="action-examples">
<title>Other Action execution examples</title>
<sect2 id="action-on-start">
<title>on-start</title>
<para>
The following example shows an action that creates a new Booking object by invoking a method on a service:
</para>
<programlisting language="xml"><![CDATA[
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
<input name="hotelId" />
<on-start>
<evaluate expression="bookingService.createBooking(hotelId, currentUser.name)"
result="flowScope.booking" />
</on-start>
</flow>]]>
</programlisting>
</sect2>
<sect2 id="action-on-state-entry">
<title>on-entry</title>
<para>
The following example shows a state entry action that sets the special <code>fragments</code> variable that causes the view-state to render a partial fragment of its view:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="changeSearchCriteria" view="enterSearchCriteria.xhtml" popup="true">
<on-entry>
<render fragments="hotelSearchForm" />
</on-entry>
</view-state>]]>
</programlisting>
</sect2>
<sect2 id="action-on-state-exit">
<title>on-exit</title>
<para>
The following example shows a state exit action that releases a lock on a record being edited:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="editOrder">
<on-entry>
<evaluate expression="orderService.selectForUpdate(orderId, currentUser)"
result="viewScope.order" />
</on-entry>
<transition on="save" to="finish">
<evaluate expression="orderService.update(order, currentUser)" />
</transition>
<on-exit>
<evaluate expression="orderService.releaseLock(order, currentUser)" />
</on-exit>
</view-state>]]>
</programlisting>
</sect2>
<sect2 id="on-end">
<title>on-end</title>
<para>
The following example shows the equivalent object locking behavior using flow start and end actions:
</para>
<programlisting language="xml"><![CDATA[
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
<input name="orderId" />
<on-start>
<evaluate expression="orderService.selectForUpdate(orderId, currentUser)"
result="flowScope.order" />
</on-start>
<view-state id="editOrder">
<transition on="save" to="finish">
<evaluate expression="orderService.update(order, currentUser)" />
</transition>
</view-state>
<on-end>
<evaluate expression="orderService.releaseLock(order, currentUser)" />
</on-end>
</flow>]]>
</programlisting>
</sect2>
<sect2 id="action-on-render">
<title>on-render</title>
<para>
The following example shows a render action that loads a list of hotels to display before the view is rendered:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="reviewHotels">
<on-render>
<evaluate expression="bookingService.findHotels(searchCriteria)"
result="viewScope.hotels" result-type="dataModel" />
</on-render>
<transition on="select" to="reviewHotel">
<set name="flowScope.hotel" value="hotels.selectedRow" />
</transition>
</view-state>]]>
</programlisting>
</sect2>
<sect2 id="action-on-transition">
<title>on-transition</title>
<para>
The following example shows a transition action adds a subflow outcome event attribute to a collection:
</para>
<programlisting language="xml"><![CDATA[
<subflow-state id="addGuest" subflow="createGuest">
<transition on="guestCreated" to="reviewBooking">
<evaluate expression="booking.guestList.add(currentEvent.attributes.newGuest)" />
</transition>
</subfow-state>]]>
</programlisting>
</sect2>
<sect2 id="named-actions">
<title>Named actions</title>
<para>
The following example shows how to execute a chain of actions in an action-state.
The name of each action becomes a qualifier for the action's result event.
</para>
<programlisting language="xml"><![CDATA[
<action-state id="doTwoThings">
<evaluate expression="service.thingOne()">
<attribute name="name" value="thingOne" />
</evaluate>
<evaluate expression="service.thingTwo()">
<attribute name="name" value="thingTwo" />
</evaluate>
<transition on="thingTwo.success" to="showResults" />
</action-state>]]>
</programlisting>
<para>
In this example, the flow will transition to <code>showResults</code> when <code>thingTwo</code>
completes successfully.
</para>
</sect2>
<sect2 id="streaming-actions">
<title>Streaming actions</title>
<para>
Sometimes an Action needs to stream a custom response back to the client.
An example might be a flow that renders a PDF document when handling a print event.
This can be achieved by having the action stream the content then record "Response Complete" status on the ExternalContext.
The responseComplete flag tells the pausing view-state not to render the response because another object has taken care of it.
</para>
<programlisting language="xml"><![CDATA[
<view-state id="reviewItinerary">
<transition on="print">
<evaluate expression="printBoardingPassAction" />
</transition>
</view-state>]]>
</programlisting>
<programlisting language="java"><![CDATA[
public class PrintBoardingPassAction extends AbstractAction {
public Event doExecute(RequestContext context) {
// stream PDF content here...
// - Access HttpServletResponse by calling context.getExternalContext().getNativeResponse();
// - Mark response complete by calling context.getExternalContext().recordResponseComplete();
return success();
}
}]]>
</programlisting>
<para>
In this example, when the print event is raised the flow will call the printBoardingPassAction.
The action will render the PDF then mark the response as complete.
</para>
</sect2>
<sect2 id="file-upload">
<title>Handling File Uploads</title>
<para>
Another common task is to use Web Flow to handle multipart file uploads in combination with Spring MVC's
<code>MultipartResolver</code>. Once the resolver is set up correctly <ulink url="http://static.springsource.org/spring/docs/2.5.x/reference/mvc.html#mvc-multipart">as described here</ulink> and the submitting
HTML form is configured with <code>enctype="multipart/form-data"</code>, you can easily handle the file upload in a
transition action.
</para>
<para>
Note that the File Upload example below below is not relevant when using Web Flow with JSF.
Check the documentation of your JSF component library to see what file upload components it provides.
</para>
<para>
Given a form such as:
</para>
<programlisting language="xml"><![CDATA[
<form:form modelAttribute="fileUploadHandler" enctype="multipart/form-data">
Select file: <input type="file" name="file"/>
<input type="submit" name="_eventId_upload" value="Upload" />
</form:form>]]>
</programlisting>
<para>
and a backing object for handling the upload such as:
</para>
<programlisting language="java"><![CDATA[
package org.springframework.webflow.samples.booking;
import org.springframework.web.multipart.MultipartFile;
public class FileUploadHandler {
private transient MultipartFile file;
public void processFile() {
//Do something with the MultipartFile here
}
public void setFile(MultipartFile file) {
this.file = file;
}
}]]>
</programlisting>
<para>
you can process the upload using a transition action as in the following example:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="uploadFile" model="uploadFileHandler">
<var name="fileUploadHandler" class="org.springframework.webflow.samples.booking.FileUploadHandler" />
<transition on="upload" to="finish" >
<evaluate expression="fileUploadHandler.processFile()"/>
</transition>
<transition on="cancel" to="finish" bind="false"/>
</view-state>]]>
</programlisting>
<para>
The <code>MultipartFile</code> will be bound to the <code>FileUploadHandler</code> bean as
part of the normal form binding process so that it will be available to process during the
execution of the transition action.
</para>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="defining-flows">
<title>Defining Flows</title>
<sect1 id="defining-flows-introduction">
<title>Introduction</title>
<para>
This chapter begins the Users Section.
It shows how to implement flows using the flow definition language.
By the end of this chapter you should have a good understanding of language constructs, and be capable of authoring a flow definition.
</para>
</sect1>
<sect1 id="flow-overview">
<title>What is a flow?</title>
<para>
A flow encapsulates a reusable sequence of steps that can execute in different contexts.
Below is a <ulink url="http://www.jjg.net/ia/visvocab/">Garrett Information Architecture</ulink> diagram illustrating a reference to a flow that encapsulates the steps of a hotel booking process:
</para>
<mediaobject>
<imageobject role="fo">
<imagedata fileref="images/hotels-site.png" format="PNG" align="center"/>
</imageobject>
<imageobject role="html">
<imagedata fileref="images/hotels-site.png" format="PNG" align="center"/>
</imageobject>
<caption>
<para>Site Map illustrating a reference to a flow</para>
</caption>
</mediaobject>
</sect1>
<sect1 id="flow-makeup">
<title>What is the makeup of a typical flow?</title>
<para>
In Spring Web Flow, a flow consists of a series of steps called "states".
Entering a state typically results in a view being displayed to the user.
On that view, user events occur that are handled by the state.
These events can trigger transitions to other states which result in view navigations.
</para>
<para>
The example below shows the structure of the book hotel flow referenced in the previous diagram:
</para>
<mediaobject>
<imageobject role="fo">
<imagedata fileref="images/hotels-site-bookhotel-flow.png" format="PNG" align="center"/>
</imageobject>
<imageobject role="html">
<imagedata fileref="images/hotels-site-bookhotel-flow.png" format="PNG" align="center"/>
</imageobject>
<caption>
<para>Flow diagram</para>
</caption>
</mediaobject>
</sect1>
<sect1 id="flow-authoring">
<title>How are flows authored?</title>
<para>
Flows are authored by web application developers using a simple XML-based flow definition language.
The next steps of this guide will walk you through the elements of this language.
</para>
</sect1>
<sect1 id="essential-flow-elements">
<title>Essential language elements</title>
<sect2 id="flow-element">
<title>flow</title>
<para>
Every flow begins with the following root element:
</para>
<programlisting language="xml"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
</flow>]]>
</programlisting>
<para>
All states of the flow are defined within this element.
The first state defined becomes the flow's starting point.
</para>
</sect2>
<sect2 id="view-state-element">
<title>view-state</title>
<para>
Use the <code>view-state</code> element to define a step of the flow that renders a view:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" />]]>
</programlisting>
<para>
By convention, a view-state maps its id to a view template in the directory where the flow is located.
For example, the state above might render <filename>/WEB-INF/hotels/booking/enterBookingDetails.xhtml</filename>
if the flow itself was located in the <filename>/WEB-INF/hotels/booking</filename> directory.
</para>
</sect2>
<sect2 id="transition-element">
<title>transition</title>
<para>
Use the <code>transition</code> element to handle events that occur within a state:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails">
<transition on="submit" to="reviewBooking" />
</view-state>]]>
</programlisting>
<para>
These transitions drive view navigations.
</para>
</sect2>
<sect2 id="end-state-element">
<title>end-state</title>
<para>
Use the <code>end-state</code> element to define a flow outcome:
</para>
<programlisting language="xml"><![CDATA[
<end-state id="bookingCancelled" />]]>
</programlisting>
<para>
When a flow transitions to a end-state it terminates and the outcome is returned.
</para>
</sect2>
<sect2 id="checkpoint-essential-language-elements">
<title>Checkpoint: Essential language elements</title>
<para>
With the three elements <code>view-state</code>, <code>transition</code>, and <code>end-state</code>, you can quickly express your view navigation logic.
Teams often do this before adding flow behaviors so they can focus on developing the user interface of the application with end users first.
Below is a sample flow that implements its view navigation logic using these elements:
</para>
<programlisting language="xml"><![CDATA[
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
<view-state id="enterBookingDetails">
<transition on="submit" to="reviewBooking" />
</view-state>
<view-state id="reviewBooking">
<transition on="confirm" to="bookingConfirmed" />
<transition on="revise" to="enterBookingDetails" />
<transition on="cancel" to="bookingCancelled" />
</view-state>
<end-state id="bookingConfirmed" />
<end-state id="bookingCancelled" />
</flow>]]>
</programlisting>
</sect2>
</sect1>
<sect1 id="flow-actions">
<title>Actions</title>
<para>
Most flows need to express more than just view navigation logic.
Typically they also need to invoke business services of the application or other actions.
</para>
<para>
Within a flow, there are several points where you can execute actions. These points are:
<itemizedlist>
<listitem><para>On flow start</para></listitem>
<listitem><para>On state entry</para></listitem>
<listitem><para>On view render</para></listitem>
<listitem><para>On transition execution</para></listitem>
<listitem><para>On state exit</para></listitem>
<listitem><para>On flow end</para></listitem>
</itemizedlist>
</para>
<para>
Actions are defined using a concise expression language. Spring Web Flow uses the Unified EL by default.
The next few sections will cover the essential language elements for defining actions.
</para>
<sect2 id="evaluate-element">
<title>evaluate</title>
<para>
The action element you will use most often is the <code>evaluate</code> element.
Use the <code>evaluate</code> element to evaluate an expression at a point within your flow.
With this single tag you can invoke methods on Spring beans or any other flow variable.
For example:
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="entityManager.persist(booking)" />]]>
</programlisting>
<sect3 id="evaluate-element-result">
<title>Assigning an evaluate result</title>
<para>
If the expression returns a value, that value can be saved in the flow's data model called <code>flowScope</code>:
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="bookingService.findHotels(searchCriteria)" result="flowScope.hotels" />]]>
</programlisting>
</sect3>
<sect3 id="evaluate-element-result-type">
<title>Converting an evaluate result</title>
<para>
If the expression returns a value that may need to be converted, specify the desired type using the <code>result-type</code> attribute:
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="bookingService.findHotels(searchCriteria)" result="flowScope.hotels"
result-type="dataModel"/>]]>
</programlisting>
</sect3>
</sect2>
<sect2 id="checkpoint-actions">
<title>Checkpoint: flow actions</title>
<para>
Now review the sample booking flow with actions added:
</para>
<programlisting language="xml"><![CDATA[
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
<input name="hotelId" />
<on-start>
<evaluate expression="bookingService.createBooking(hotelId, currentUser.name)"
result="flowScope.booking" />
</on-start>
<view-state id="enterBookingDetails">
<transition on="submit" to="reviewBooking" />
</view-state>
<view-state id="reviewBooking">
<transition on="confirm" to="bookingConfirmed" />
<transition on="revise" to="enterBookingDetails" />
<transition on="cancel" to="bookingCancelled" />
</view-state>
<end-state id="bookingConfirmed" />
<end-state id="bookingCancelled" />
</flow>]]>
</programlisting>
<para>
This flow now creates a Booking object in flow scope when it starts.
The id of the hotel to book is obtained from a flow input attribute.
</para>
</sect2>
</sect1>
<sect1 id="flow-inputoutput">
<title>Input/Output Mapping</title>
<para>
Each flow has a well-defined input/output contract.
Flows can be passed input attributes when they start, and can return output attributes when they end.
In this respect, calling a flow is conceptually similar to calling a method with the following signature:
</para>
<programlisting language="java"><![CDATA[
FlowOutcome flowId(Map<String, Object> inputAttributes);]]>
</programlisting>
<para>
... where a <code>FlowOutcome</code> has the following signature:
</para>
<programlisting language="java"><![CDATA[
public interface FlowOutcome {
public String getName();
public Map<String, Object> getOutputAttributes();
}]]>
</programlisting>
<sect2 id="input-element">
<title>input</title>
<para>
Use the <code>input</code> element to declare a flow input attribute:
</para>
<programlisting language="xml"><![CDATA[
<input name="hotelId" />]]>
</programlisting>
<para>
Input values are saved in flow scope under the name of the attribute.
For example, the input above would be saved under the name <code>hotelId</code>.
</para>
<sect3 id="input-element-type">
<title>Declaring an input type</title>
<para>
Use the <code>type</code> attribute to declare the input attribute's type:
</para>
<programlisting language="xml"><![CDATA[
<input name="hotelId" type="long" />]]>
</programlisting>
<para>
If an input value does not match the declared type, a type conversion will be attempted.
</para>
</sect3>
<sect3 id="input-element-value">
<title>Assigning an input value</title>
<para>
Use the <code>value</code> attribute to specify an expression to assign the input value to:
</para>
<programlisting language="xml"><![CDATA[
<input name="hotelId" value="flowScope.myParameterObject.hotelId" />]]>
</programlisting>
<para>
If the expression's value type can be determined, that metadata will be used for type coersion if no <code>type</code> attribute is specified.
</para>
</sect3>
<sect3 id="input-element-required">
<title>Marking an input as required</title>
<para>
Use the <code>required</code> attribute to enforce the input is not null or empty:
</para>
<programlisting language="xml"><![CDATA[
<input name="hotelId" type="long" value="flowScope.hotelId" required="true" />]]>
</programlisting>
</sect3>
</sect2>
<sect2 id="output-element">
<title>output</title>
<para>
Use the <code>output</code> element to declare a flow output attribute.
Output attributes are declared within end-states that represent specific flow outcomes.
</para>
<programlisting language="xml"><![CDATA[
<end-state id="bookingConfirmed">
<output name="bookingId" />
</end-state>]]>
</programlisting>
<para>
Output values are obtained from flow scope under the name of the attribute.
For example, the output above would be assigned the value of the <code>bookingId</code> variable.
</para>
<sect3 id="output-element-value">
<title>Specifying the source of an output value</title>
<para>
Use the <code>value</code> attribute to denote a specific output value expression:
</para>
<programlisting language="xml"><![CDATA[
<output name="confirmationNumber" value="booking.confirmationNumber" />]]>
</programlisting>
</sect3>
</sect2>
<sect2 id="checkpoint-input-output">
<title>Checkpoint: input/output mapping</title>
<para>
Now review the sample booking flow with input/output mapping:
</para>
<programlisting language="xml"><![CDATA[
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
<input name="hotelId" />
<on-start>
<evaluate expression="bookingService.createBooking(hotelId, currentUser.name)"
result="flowScope.booking" />
</on-start>
<view-state id="enterBookingDetails">
<transition on="submit" to="reviewBooking" />
</view-state>
<view-state id="reviewBooking">
<transition on="confirm" to="bookingConfirmed" />
<transition on="revise" to="enterBookingDetails" />
<transition on="cancel" to="bookingCancelled" />
</view-state>
<end-state id="bookingConfirmed" >
<output name="bookingId" value="booking.id"/>
</end-state>
<end-state id="bookingCancelled" />
</flow>]]>
</programlisting>
<para>
The flow now accepts a <code>hotelId</code> input attribute and returns a <code>bookingId</code> output attribute
when a new booking is confirmed.
</para>
</sect2>
</sect1>
<sect1 id="flow-variables">
<title>Variables</title>
<para>
A flow may declare one or more instance variables.
These variables are allocated when the flow starts.
Any <code>@Autowired</code> transient references the variable holds are also rewired when the flow resumes.
</para>
<sect2 id="var-element">
<title>var</title>
<para>
Use the <code>var</code> element to declare a flow variable:
</para>
<programlisting language="xml"><![CDATA[
<var name="searchCriteria" class="com.mycompany.myapp.hotels.search.SearchCriteria"/>]]>
</programlisting>
<para>
Make sure your variable's class implements <code>java.io.Serializable</code>, as the instance state is saved between flow requests.
</para>
</sect2>
</sect1>
<sect1 id="calling-subflows">
<title>Calling subflows</title>
<para>
A flow may call another flow as a subflow. The flow will wait until the subflow returns, then respond to the subflow outcome.
</para>
<sect2 id="subflow-state-element">
<title>subflow-state</title>
<para>
Use the <code>subflow-state</code> element to call another flow as a subflow:
</para>
<programlisting language="xml"><![CDATA[
<subflow-state id="addGuest" subflow="createGuest">
<transition on="guestCreated" to="reviewBooking">
<evaluate expression="booking.guests.add(currentEvent.attributes.guest)" />
</transition>
<transition on="creationCancelled" to="reviewBooking" />
</subflow-state>]]>
</programlisting>
<para>
The above example calls the <code>createGuest</code> flow, then waits for it to return.
When the flow returns with a <code>guestCreated</code> outcome, the new guest is added to the booking's guest list.
</para>
<sect3 id="subflow-state-element-input">
<title>Passing a subflow input</title>
<para>
Use the <code>input</code> element to pass input to the subflow:
</para>
<programlisting language="xml"><![CDATA[
<subflow-state id="addGuest" subflow="createGuest">
<input name="booking" />
<transition to="reviewBooking" />
</subflow-state>]]>
</programlisting>
</sect3>
<sect3 id="subflow-state-element-output">
<title>Mapping subflow output</title>
<para>
Simply refer to a subflow output attribute by its name within a outcome transition:
</para>
<programlisting language="xml"><![CDATA[
<transition on="guestCreated" to="reviewBooking">
<evaluate expression="booking.guests.add(currentEvent.attributes.guest)" />
</transition>]]>
</programlisting>
<para>
In the above example, <code>guest</code> is the name of an output attribute returned by the <code>guestCreated</code> outcome.
</para>
</sect3>
</sect2>
<sect2 id="checkpoint-subflow">
<title>Checkpoint: calling subflows</title>
<para>
Now review the sample booking flow calling a subflow:
</para>
<programlisting language="xml"><![CDATA[
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
<input name="hotelId" />
<on-start>
<evaluate expression="bookingService.createBooking(hotelId, currentUser.name)"
result="flowScope.booking" />
</on-start>
<view-state id="enterBookingDetails">
<transition on="submit" to="reviewBooking" />
</view-state>
<view-state id="reviewBooking">
<transition on="addGuest" to="addGuest" />
<transition on="confirm" to="bookingConfirmed" />
<transition on="revise" to="enterBookingDetails" />
<transition on="cancel" to="bookingCancelled" />
</view-state>
<subflow-state id="addGuest" subflow="createGuest">
<transition on="guestCreated" to="reviewBooking">
<evaluate expression="booking.guests.add(currentEvent.attributes.guest)" />
</transition>
<transition on="creationCancelled" to="reviewBooking" />
</subflow-state>
<end-state id="bookingConfirmed" >
<output name="bookingId" value="booking.id" />
</end-state>
<end-state id="bookingCancelled" />
</flow>]]>
</programlisting>
<para>
The flow now calls a <code>createGuest</code> subflow to add a new guest to the guest list.
</para>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="el">
<title>Expression Language (EL)</title>
<sect1 id="el-introduction">
<title>Introduction</title>
<para>
Web Flow uses EL to access its data model and to invoke actions.
This chapter will familiarize you with EL syntax, configuration, and special EL variables you can reference from your flow definition.
</para>
<para>
EL is used for many things within a flow including:
</para>
<orderedlist>
<listitem><para>Access client data such as declaring flow inputs or referencing request parameters.</para></listitem>
<listitem><para>Access data in Web Flow's <code>RequestContext</code> such as <code>flowScope</code> or <code>currentEvent</code>.</para></listitem>
<listitem><para>Invoke methods on Spring-managed objects through actions.</para></listitem>
<listitem><para>Resolve expressions such as state transition criteria, subflow ids, and view names.</para></listitem>
</orderedlist>
<para>
EL is also used to bind form parameters to model objects and reversely to render formatted form fields from the properties of a model object.
That however does not apply when using Web Flow with JSF in which case the standard JSF component lifecyle applies.
</para>
<sect2 id="el-types">
<title>Expression types</title>
<para>
An important concept to understand is there are two types of expressions in Web Flow: standard expressions and template expressions.
</para>
<sect3 id="el-types-eval">
<title>Standard Expressions</title>
<para>
The first and most common type of expression is the <emphasis>standard expression</emphasis>.
Such expressions are evaluated directly by the EL and need not be enclosed in delimiters like <code>#{}</code>.
For example:
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="searchCriteria.nextPage()" />]]>
</programlisting>
<para>
The expression above is a standard expression that invokes the <code>nextPage</code> method on the <code>searchCriteria</code> variable when evaluated.
If you attempt to enclose this expression in a special delimiter like <code>#{}</code> you will get an <code>IllegalArgumentException</code>.
In this context the delimiter is seen as redundant.
The only acceptable value for the <code>expression</code> attribute is an single expression string.
</para>
</sect3>
<sect3 id="el-types-template">
<title>Template expressions</title>
<para>
The second type of expression is a <emphasis>template expression</emphasis>.
A template expression allows mixing of literal text with one or more standard expressions.
Each standard expression block is explicitly surrounded with the <code>#{}</code> delimiters.
For example:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="error" view="error-#{externalContext.locale}.xhtml" />]]>
</programlisting>
<para>
The expression above is a template expression.
The result of evaluation will be a string that concatenates literal text such as <code>error-</code> and <code>.xhtml</code> with the result of evaluating <code>externalContext.locale</code>.
As you can see, explicit delimiters are necessary here to demarcate standard expression blocks within the template.
</para>
<note>
<para>
See the Web Flow XML schema for a complete listing of those XML attributes that accept standard expressions and those that accept template expressions.
You can also use F2 in Eclipse (or equivalent shortcut in other IDEs) to access available documentation when typing out specific flow definition attributes.
</para>
</note>
</sect3>
</sect2>
</sect1>
<sect1 id="el-language-choices">
<title>EL Implementations</title>
<sect2 id="el-spring-el">
<title>Spring EL</title>
<para>
Starting with version 2.1 Web Flow uses the <ulink url="http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/expressions.html">Spring Expression Language</ulink> (Spring EL).
Spring EL was created to provide is a single, well-supported expression language for use across all the products in the Spring portfolio.
It is distributed as a separate jar <code>org.springframework.expression</code> in the Spring Framework.
Existing applications will need to remove dependencies on <code>org.jboss.el</code> or <code>org.ognl</code> and use <code>org.springframework.expression</code> instead.
See the section below on EL Portability for other notes on upgrading.
</para>
</sect2>
<sect2 id="el-unified-el">
<title>Unified EL</title>
<para>
In Web Flow 2.0 <ulink url="http://en.wikipedia.org/wiki/Unified_Expression_Language">Unified EL</ulink> was the default expression language with <code>jboss-el</code> as the implementation.
Use of Unified EL also implies a dependency on <code>el-api</code> although that is typically <emphasis>provided</emphasis> by your web container.
Tomcat 6 includes it, for example.
Spring EL is the default and recommended expression language to use.
However it is possible to replace it with Unified EL if you wish to do so.
You need the following Spring configuration to plug in the <code>WebFlowELExpressionParser</code> to the <code>flow-builder-services</code>:
<programlisting language="xml"><![CDATA[
<webflow:flow-builder-services expression-parser="expressionParser"/>
<bean id="expressionParser" class="org.springframework.webflow.expression.el.WebFlowELExpressionParser">
<constructor-arg>
<bean class="org.jboss.el.ExpressionFactoryImpl" />
</constructor-arg>
</bean>]]>
</programlisting>
Note that if your application is registering custom converters it's important to ensure the WebFlowELExpressionParser is configured with the conversion service that has those custom converters.
<programlisting language="xml"><![CDATA[
<webflow:flow-builder-services expression-parser="expressionParser" conversion-service="conversionService"/>
<bean id="expressionParser" class="org.springframework.webflow.expression.el.WebFlowELExpressionParser">
<constructor-arg>
<bean class="org.jboss.el.ExpressionFactoryImpl" />
</constructor-arg>
<property name="conversionService" ref="conversionService"/>
</bean>
<bean id="conversionService" class="somepackage.ApplicationConversionService"/>]]>
</programlisting>
</para>
</sect2>
<sect2 id="el-ognl">
<title>OGNL</title>
<para>
<ulink url="http://www.ognl.org">OGNL</ulink> is the third supported expression language.
OGNL is the EL most familiar to Web Flow version 1.0 users.
Please refer to the <ulink url="http://www.ognl.org/2.6.9/Documentation/html/LanguageGuide/index.html">OGNL language guide</ulink> for specifics on its EL syntax.
If you wish to use OGNL this is the Spring configuration necessary to plug it in:
<programlisting language="xml"><![CDATA[
<webflow:flow-builder-services expression-parser="expressionParser"/>
<bean id="expressionParser" class="org.springframework.webflow.expression.WebFlowOgnlExpressionParser"/>]]>
</programlisting>
Note that if your application is registering custom converters it's important to ensure the WebFlowOgnlExpressionParser is configured with the conversion service that has those custom converters.
<programlisting language="xml"><![CDATA[
<webflow:flow-builder-services expression-parser="expressionParser" conversion-service="conversionService"/>
<bean id="expressionParser" class="org.springframework.webflow.expression.WebFlowOgnlExpressionParser">
<property name="conversionService" ref="conversionService"/>
</bean>
<bean id="conversionService" class="somepackage.ApplicationConversionService"/>]]>
</programlisting>
</para>
</sect2>
</sect1>
<sect1 id="el-portability">
<title>EL portability</title>
<para>
In general, you will find Spring EL, Unified EL and OGNL to have a very similar syntax.
</para>
<para>
Note however there are some advantages to Spring EL.
For example Spring EL is closely integrated with the type conversion of Spring 3 and that allows you to take full advantage of its features.
Specifically the automatic detection of generic types as well as the use of formatting annotations is currently supported with Spring EL only.
</para>
<para>
There are some minor changes to keep in mind when upgrading to Spring EL from Unified EL or OGNL as follows:
<orderedlist>
<listitem><para>Expressions deliniated with <code>${}</code> in flow definitions must be changed to <code>#{}</code>.</para></listitem>
<listitem><para>Expressions testing the current event <code>#{currentEvent == 'submit'}</code> must be changed to <code>#{currentEvent.id == 'submit'}</code>.</para></listitem>
<listitem>
<para>
Resolving properties such as <code>#{currentUser.name}</code> may cause NullPointerException without any checks such as <code>#{currentUser != null ? currentUser.name : null}</code>.
A much better alternative though is the safe navigation operator <code>#{currentUser?.name}</code>.
</para>
</listitem>
</orderedlist>
For more information on Spring EL syntax please refer to the <ulink url="http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/expressions.html#expressions-language-ref">Language Reference</ulink> section in the Spring Documentation.
</para>
</sect1>
<sect1 id="el-variables">
<title>Special EL variables</title>
<para>
There are several implicit variables you may reference from within a flow.
These variables are discussed in this section.
</para>
<para>
Keep in mind this general rule.
Variables referring to data scopes (flowScope, viewScope, requestScope, etc.) should only be used when assigning a new variable to one of the scopes.
</para>
<para>
For example when assigning the result of the call to <code>bookingService.findHotels(searchCriteria)</code> to a new variable called "hotels" you must prefix it with a scope variable in order to let Web Flow know where you want it stored:
<programlisting language="xml"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<flow xmlns="http://www.springframework.org/schema/webflow" ... >
<var name="searchCriteria" class="org.springframework.webflow.samples.booking.SearchCriteria" />
<view-state id="reviewHotels">
<on-render>
<evaluate expression="bookingService.findHotels(searchCriteria)" result="viewScope.hotels" />
</on-render>
</view-state>
</flow>]]>
</programlisting>
However when setting an existing variable such as "searchCriteria" in the example below, you reference the variable directly without prefixing it with any scope variables:
<programlisting language="xml"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<flow xmlns="http://www.springframework.org/schema/webflow" ... >
<var name="searchCriteria" class="org.springframework.webflow.samples.booking.SearchCriteria" />
<view-state id="reviewHotels">
<transition on="sort">
<set name="searchCriteria.sortBy" value="requestParameters.sortBy" />
</transition>
</view-state>
</flow>]]>
</programlisting>
</para>
<para>
The following is the list of implicit variables you can reference within a flow definition:
</para>
<sect2 id="el-variable-flowScope">
<title>flowScope</title>
<para>
Use <code>flowScope</code> to assign a flow variable.
Flow scope gets allocated when a flow starts and destroyed when the flow ends. With the default
implementation, any objects stored in flow scope need to be Serializable.
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="searchService.findHotel(hotelId)" result="flowScope.hotel" />]]>
</programlisting>
</sect2>
<sect2 id="el-variable-viewScope">
<title>viewScope</title>
<para>
Use <code>viewScope</code> to assign a view variable.
View scope gets allocated when a <code>view-state</code> enters and destroyed when the state exits.
View scope is <emphasis>only</emphasis> referenceable from within a <code>view-state</code>. With the
default implementation, any objects stored in view scope need to be Serializable.
</para>
<programlisting language="xml"><![CDATA[
<on-render>
<evaluate expression="searchService.findHotels(searchCriteria)" result="viewScope.hotels"
result-type="dataModel" />
</on-render>]]>
</programlisting>
</sect2>
<sect2 id="el-variable-requestScope">
<title>requestScope</title>
<para>
Use <code>requestScope</code> to assign a request variable.
Request scope gets allocated when a flow is called and destroyed when the flow returns.
</para>
<programlisting language="xml"><![CDATA[
<set name="requestScope.hotelId" value="requestParameters.id" type="long" />]]>
</programlisting>
</sect2>
<sect2 id="el-variable-flashScope">
<title>flashScope</title>
<para>
Use <code>flashScope</code> to assign a flash variable.
Flash scope gets allocated when a flow starts, cleared after every view render, and destroyed when the
flow ends. With the default implementation, any objects stored in flash scope need to be Serializable.
</para>
<programlisting language="xml"><![CDATA[
<set name="flashScope.statusMessage" value="'Booking confirmed'" />]]>
</programlisting>
</sect2>
<sect2 id="el-variable-conversationScope">
<title>conversationScope</title>
<para>
Use <code>conversationScope</code> to assign a conversation variable.
Conversation scope gets allocated when a top-level flow starts and destroyed when the top-level flow ends.
Conversation scope is shared by a top-level flow and all of its subflows. With the default
implementation, conversation scoped objects are stored in the HTTP session and should generally be
Serializable to account for typical session replication.
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="searchService.findHotel(hotelId)" result="conversationScope.hotel" />]]>
</programlisting>
</sect2>
<sect2 id="el-variable-requestParameters">
<title>requestParameters</title>
<para>
Use <code>requestParameters</code> to access a client request parameter:
</para>
<programlisting language="xml"><![CDATA[
<set name="requestScope.hotelId" value="requestParameters.id" type="long" />]]>
</programlisting>
</sect2>
<sect2 id="el-variable-currentEvent">
<title>currentEvent</title>
<para>
Use <code>currentEvent</code> to access attributes of the current <code>Event</code>:
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="booking.guests.add(currentEvent.attributes.guest)" />]]>
</programlisting>
</sect2>
<sect2 id="el-variable-currentUser">
<title>currentUser</title>
<para>
Use <code>currentUser</code> to access the authenticated <code>Principal</code>:
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="bookingService.createBooking(hotelId, currentUser.name)"
result="flowScope.booking" />]]>
</programlisting>
</sect2>
<sect2 id="el-variable-messageContext">
<title>messageContext</title>
<para>
Use <code>messageContext</code> to access a context for retrieving and creating flow execution messages, including error and success messages.
See the <code>MessageContext</code> Javadocs for more information.
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="bookingValidator.validate(booking, messageContext)" />]]>
</programlisting>
</sect2>
<sect2 id="el-variable-resourceBundle">
<title>resourceBundle</title>
<para>
Use <code>resourceBundle</code> to access a message resource.
</para>
<programlisting language="xml"><![CDATA[
<set name="flashScope.successMessage" value="resourceBundle.successMessage" />]]>
</programlisting>
</sect2>
<sect2 id="el-variable-requestContext">
<title>flowRequestContext</title>
<para>
Use <code>flowRequestContext</code> to access the <code>RequestContext</code> API, which is a representation of the current flow request.
See the API Javadocs for more information.
</para>
</sect2>
<sect2 id="el-variable-flowExecutionContext">
<title>flowExecutionContext</title>
<para>
Use <code>flowExecutionContext</code> to access the <code>FlowExecutionContext</code> API, which is a representation of the current flow state.
See the API Javadocs for more information.
</para>
</sect2>
<sect2 id="el-variable-flowExecutionUrl">
<title>flowExecutionUrl</title>
<para>
Use <code>flowExecutionUrl</code> to access the context-relative URI for the current flow execution view-state.
</para>
</sect2>
<sect2 id="el-variable-externalContext">
<title>externalContext</title>
<para>
Use <code>externalContext</code> to access the client environment, including user session attributes.
See the <code>ExternalContext</code> API JavaDocs for more information.
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="searchService.suggestHotels(externalContext.sessionMap.userProfile)"
result="viewScope.hotels" />]]>
</programlisting>
</sect2>
</sect1>
<sect1 id="el-scope-searching">
<title>Scope searching algorithm</title>
<para>
As mentioned earlier in this section when assigning a variable in one of the flow scopes, referencing that scope is required.
For example:
</para>
<programlisting language="xml"><![CDATA[
<set name="requestScope.hotelId" value="requestParameters.id" type="long" />]]>
</programlisting>
<para>
When simply accessing a variable in one of the scopes, referencing the scope is optional.
For example:
</para>
<programlisting language="xml"><![CDATA[
<evaluate expression="entityManager.persist(booking)" />]]>
</programlisting>
<para>
When no scope is specified, like in the use of <code>booking</code> above, a scope searching algorithm is used.
The algorithm will look in request, flash, view, flow, and conversation scope for the variable.
If no such variable is found, an <code>EvaluationException</code> will be thrown.
</para>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="flow-inheritance">
<title>Flow Inheritance</title>
<sect1 id="flow-inheritance-introduction">
<title>Introduction</title>
<para>
Flow inheritance allows one flow to inherit the configuration of another flow.
Inheritance can occur at both the flow and state levels.
A common use case is for a parent flow to define global transitions and exception handlers, then each child flow can inherit those settings.
</para>
<para>
In order for a parent flow to be found, it must be added to the <code>flow-registry</code> just like any other flow.
</para>
</sect1>
<sect1 id="flow-inheritance-java-comparison">
<title>Is flow inheritance like Java inheritance?</title>
<para>
Flow inheritance is similar to Java inheritance in that elements defined in a parent are exposed via the child, however, there are key differences.
</para>
<para>
A child flow cannot override an element from a parent flow.
Similar elements between the parent and child flows will be merged.
Unique elements in the parent flow will be added to the child.
</para>
<para>
A child flow can inherit from multiple parent flows.
Java inheritance is limited to a single class.
</para>
</sect1>
<sect1 id="flow-inheritance-levels">
<title>Types of Flow Inheritance</title>
<sect2 id="flow-inheritance-level-flow">
<title>Flow level inheritance</title>
<para>
Flow level inheritance is defined by the <code>parent</code> attribute on the <code>flow</code> element.
The attribute contains a comma separated list of flow identifiers to inherit from.
The child flow will inherit from each parent in the order it is listed adding elements and content to the resulting flow.
The resulting flow from the first merge will be considered the child in the second merge, and so on.
</para>
<programlisting language="xml"><![CDATA[
<flow parent="common-transitions, common-states">]]>
</programlisting>
</sect2>
<sect2 id="flow-inheritance-level-state">
<title>State level inheritance</title>
<para>
State level inheritance is similar to flow level inheritance, except only one state inherits from the parent, instead of the entire flow.
</para>
<para>
Unlike flow inheritance, only a single parent is allowed.
Additionally, the identifier of the flow state to inherit from must also be defined.
The identifiers for the flow and the state within that flow are separated by a #.
</para>
<para>
The parent and child states must be of the same type.
For instance a view-state cannot inherit from an end-state, only another view-state.
</para>
<programlisting language="xml"><![CDATA[
<view-state id="child-state" parent="parent-flow#parent-view-state">]]>
</programlisting>
</sect2>
</sect1>
<sect1 id="flow-inheritance-abstract">
<title>Abstract flows</title>
<para>
Often parent flows are not designed to be executed directly.
In order to protect these flows from running, they can be marked as <code>abstract</code>.
If an abstract flow attempts to run, a <code>FlowBuilderException</code> will be thrown.
</para>
<programlisting language="xml"><![CDATA[
<flow abstract="true">]]>
</programlisting>
</sect1>
<sect1 id="flow-inheritance-algorithm">
<title>Inheritance Algorithm</title>
<para>
When a child flow inherits from it's parent, essentially what happens is that the parent and child are merged together to create a new flow.
There are rules for every element in the Web Flow definition language that govern how that particular element is merged.
</para>
<para>
There are two types of elements: <emphasis>mergeable</emphasis> and <emphasis>non-mergeable</emphasis>.
Mergeable elements will always attempt to merge together if the elements are similar.
Non-mergeable elements in a parent or child flow will always be contained in the resulting flow intact.
They will not be modified as part of the merge process.
</para>
<note>
<para>
Paths to external resources in the parent flow should be absolute.
Relative paths will break when the two flows are merged unless the parent and child flow are in the same directory.
Once merged, all relative paths in the parent flow will become relative to the child flow.
</para>
</note>
<sect2 id="flow-inheritance-algorithm-mergeable">
<title>Mergeable Elements</title>
<para>
If the elements are of the same type and their keyed attribute are identical, the content of the parent element will be merged with the child element.
The merge algorithm will continue to merge each sub-element of the merging parent and child.
Otherwise the parent element is added as a new element to the child.
</para>
<para>
In most cases, elements from a parent flow that are added will be added after elements in the child flow.
Exceptions to this rule include action elements (evaluate, render and set) which will be added at the beginning.
This allows for the results of parent actions to be used by child actions.
</para>
<para>
Mergeable elements are:
<itemizedlist>
<listitem>
<para>action-state: id</para>
</listitem>
<listitem>
<para>attribute: name</para>
</listitem>
<listitem>
<para>decision-state: id</para>
</listitem>
<listitem>
<para>end-state: id</para>
</listitem>
<listitem>
<para>flow: always merges</para>
</listitem>
<listitem>
<para>if: test</para>
</listitem>
<listitem>
<para>on-end: always merges</para>
</listitem>
<listitem>
<para>on-entry: always merges</para>
</listitem>
<listitem>
<para>on-exit: always merges</para>
</listitem>
<listitem>
<para>on-render: always merges</para>
</listitem>
<listitem>
<para>on-start: always merges</para>
</listitem>
<listitem>
<para>input: name</para>
</listitem>
<listitem>
<para>output: name</para>
</listitem>
<listitem>
<para>secured: attributes</para>
</listitem>
<listitem>
<para>subflow-state: id</para>
</listitem>
<listitem>
<para>transition: on and on-exception</para>
</listitem>
<listitem>
<para>view-state: id</para>
</listitem>
</itemizedlist>
</para>
</sect2>
<sect2 id="flow-inheritance-nonmergeable">
<title>Non-mergeable Elements</title>
<para>
Non-mergeable elements are:
<itemizedlist>
<listitem>
<para>bean-import</para>
</listitem>
<listitem>
<para>evaluate</para>
</listitem>
<listitem>
<para>exception-handler</para>
</listitem>
<listitem>
<para>persistence-context</para>
</listitem>
<listitem>
<para>render</para>
</listitem>
<listitem>
<para>set</para>
</listitem>
<listitem>
<para>var</para>
</listitem>
</itemizedlist>
</para>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="flow-managed-persistence">
<title>Flow Managed Persistence</title>
<sect1 id="flow-managed-persistence-introduction">
<title>Introduction</title>
<para>
Most applications access data in some way.
Many modify data shared by multiple users and therefore require transactional data access properties.
They often transform relational data sets into domain objects to support application processing.
Web Flow offers "flow managed persistence" where a flow can create, commit, and close a object persistence context for you.
Web Flow integrates both Hibernate and JPA object persistence technologies.
</para>
<para>
Apart from flow-managed persistence, there is the pattern of fully encapsulating PersistenceContext management within the service layer of your application.
In that case, the web layer does not get involved with persistence, instead it works entirely with detached objects that are passed to and returned by your service layer.
This chapter will focus on the flow-managed persistence, exploring how and when to use this feature.
</para>
</sect1>
<sect1 id="flowScopedPersistenceContext">
<title>FlowScoped PersistenceContext</title>
<para>
This pattern creates a <code>PersistenceContext</code> in <code>flowScope</code> on flow startup,
uses that context for data access during the course of flow execution, and commits changes made to persistent entities at the end.
This pattern provides isolation of intermediate edits by only committing changes to the database at the end of flow execution.
This pattern is often used in conjunction with an optimistic locking strategy to protect the integrity of data modified in parallel by multiple users.
To support saving and restarting the progress of a flow over an extended period of time, a durable store for flow state must be used.
If a save and restart capability is not required, standard HTTP session-based storage of flow state is sufficient.
In that case, session expiration or termination before commit could potentially result in changes being lost.
</para>
<para>
To use the FlowScoped PersistenceContext pattern, first mark your flow as a <code>persistence-context</code>:
</para>
<programlisting language="xml"><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow
http://www.springframework.org/schema/webflow/spring-webflow-2.0.xsd">
<persistence-context />
</flow>
]]></programlisting>
<para>
Then configure the correct <code>FlowExecutionListener</code> to apply this pattern to your flow.
If using Hibernate, register the <code>HibernateFlowExecutionListener</code>. If using JPA, register the <code>JpaFlowExecutionListener</code>.
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-executor id="flowExecutor" flow-registry="flowRegistry">
<webflow:flow-execution-listeners>
<webflow:listener ref="jpaFlowExecutionListener" />
</webflow:flow-execution-listeners>
</webflow:flow-executor>
<bean id="jpaFlowExecutionListener"
class="org.springframework.webflow.persistence.JpaFlowExecutionListener">
<constructor-arg ref="entityManagerFactory" />
<constructor-arg ref="transactionManager" />
</bean>
]]></programlisting>
<para>
To trigger a commit at the end, annotate your end-state with the commit attribute:
</para>
<para>
<programlisting language="xml"><![CDATA[
<end-state id="bookingConfirmed" commit="true" />
]]></programlisting>
</para>
<para>
That is it. When your flow starts, the listener will handle allocating a new <code>EntityManager</code> in <code>flowScope</code>.
Reference this EntityManager at anytime from within your flow by using the special <code>persistenceContext</code> variable.
In addition, any data access that occurs using a Spring managed data access object will use this EntityManager automatically.
Such data access operations should always execute non transactionally or in read-only transactions to maintain isolation of intermediate edits.
</para>
</sect1>
<sect1 id="flow-managed-persistence-propagation">
<title>Flow Managed Persistence And Sub-Flows</title>
<para>
A flow managed <code>PersistenceContext</code> is automatically extended
(propagated) to subflows assuming the subflow also has the <code>&lt;perstistence-context/&gt;</code>
variable. When a subflow re-uses the <code>PersistenceContext</code> started by its parent it ignores
commit flags when an end state is reached thereby deferring the final decision (to commit or not) to
its parent.
</para>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="flow-security">
<title>Securing Flows</title>
<sect1 id="flow-security-introduction">
<title>Introduction</title>
<para>
Security is an important concept for any application.
End users should not be able to access any portion of a site simply by guessing the URL.
Areas of a site that are sensitive must ensure that only authorized requests are processed.
Spring Security is a proven security platform that can integrate with your application at multiple levels.
This section will focus on securing flow execution.
</para>
</sect1>
<sect1 id="flow-security-how-to">
<title>How do I secure a flow?</title>
<para>
Securing flow execution is a three step process:
<itemizedlist>
<listitem><para>Configure Spring Security with authentication and authorization rules</para></listitem>
<listitem><para>Annotate the flow definition with the secured element to define the security rules</para></listitem>
<listitem><para>Add the SecurityFlowExecutionListener to process the security rules.</para></listitem>
</itemizedlist>
</para>
<para>
Each of these steps must be completed or else flow security rules will not be applied.
</para>
</sect1>
<sect1 id="flow-security-secured-element">
<title>The secured element</title>
<para>
The secured element designates that its containing element should apply the authorization check before fully entering.
This may not occur more then once per stage of the flow execution that is secured.
</para>
<para>
Three phases of flow execution can be secured: flows, states and transitions.
In each case the syntax for the secured element is identical.
The secured element is located inside the element it is securing.
For example, to secure a state the secured element occurs directly inside that state:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="secured-view">
<secured attributes="ROLE_USER" />
...
</view-state>]]>
</programlisting>
<sect2 id="flow-security-secured-element-attributes">
<title>Security attributes</title>
<para>
The <code>attributes</code> attribute is a comma separated list of Spring Security authorization attributes.
Often, these are specific security roles.
The attributes are compared against the user's granted attributes by a Spring Security access decision manager.
</para>
<programlisting language="xml"><![CDATA[
<secured attributes="ROLE_USER" />]]>
</programlisting>
<para>
By default, a role based access decision manager is used to determine if the user is allowed access.
This will need to be overridden if your application is not using authorization roles.
</para>
</sect2>
<sect2 id="flow-security-secured-element-match">
<title>Matching type</title>
<para>
There are two types of matching available: <code>any</code> and <code>all</code>.
Any, allows access if at least one of the required security attributes is granted to the user.
All, allows access only if each of the required security attributes are granted to the user.
</para>
<programlisting language="xml"><![CDATA[
<secured attributes="ROLE_USER, ROLE_ANONYMOUS" match="any" />]]>
</programlisting>
<para>
This attribute is optional.
If not defined, the default value is <code>any</code>.
</para>
<para>
The <code>match</code> attribute will only be respected if the default access decision manager is used.
</para>
</sect2>
</sect1>
<sect1 id="flow-security-listener">
<title>The SecurityFlowExecutionListener</title>
<para>
Defining security rules in the flow by themselves will not protect the flow execution.
A <code>SecurityFlowExecutionListener</code> must also be defined in the webflow configuration and applied to the flow executor.
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-executor id="flowExecutor" flow-registry="flowRegistry">
<webflow:flow-execution-listeners>
<webflow:listener ref="securityFlowExecutionListener" />
</webflow:flow-execution-listeners>
</webflow:flow-executor>
<bean id="securityFlowExecutionListener"
class="org.springframework.webflow.security.SecurityFlowExecutionListener" />
]]></programlisting>
<para>
If access is denied to a portion of the application an <code>AccessDeniedException</code> will be thrown.
This exception will later be caught by Spring Security and used to prompt the user to authenticate.
It is important that this exception be allowed to travel up the execution stack uninhibited, otherwise the end user may not be prompted to authenticate.
</para>
<sect2 id="flow-security-listener-adm">
<title>Custom Access Decision Managers</title>
<para>
If your application is using authorities that are not role based, you will need to configure a custom <code>AccessDecisionManager</code>.
You can override the default decision manager by setting the <code>accessDecisionManager</code> property on the security listener.
Please consult the <ulink url="http://static.springframework.org/spring-security/site/reference.html">Spring Security reference documentation</ulink> to learn more about decision managers.
</para>
<programlisting language="xml"><![CDATA[
<bean id="securityFlowExecutionListener"
class="org.springframework.webflow.security.SecurityFlowExecutionListener">
<property name="accessDecisionManager" ref="myCustomAccessDecisionManager" />
</bean>
]]></programlisting>
</sect2>
</sect1>
<sect1 id="flow-security-configuration">
<title>Configuring Spring Security</title>
<para>
Spring Security has robust configuration options available.
As every application and environment has its own security requirements, the <ulink url="http://static.springframework.org/spring-security/site/reference.html">Spring Security reference documentation</ulink> is the best place to learn the available options.
</para>
<para>
Both the <code>booking-faces</code> and <code>booking-mvc</code> sample applications are configured to use Spring Security.
Configuration is needed at both the Spring and web.xml levels.
</para>
<sect2 id="flow-security-configuration-spring">
<title>Spring configuration</title>
<para>
The Spring configuration defines <code>http</code> specifics (such as protected URLs and login/logout mechanics) and the <code>authentication-provider</code>.
For the sample applications, a local authentication provider is configured.
</para>
<programlisting language="xml"><![CDATA[
<security:http auto-config="true">
<security:form-login login-page="/spring/login"
login-processing-url="/spring/loginProcess"
default-target-url="/spring/main"
authentication-failure-url="/spring/login?login_error=1" />
<security:logout logout-url="/spring/logout" logout-success-url="/spring/logout-success" />
</security:http>
<security:authentication-provider>
<security:password-encoder hash="md5" />
<security:user-service>
<security:user name="keith" password="417c7382b16c395bc25b5da1398cf076"
authorities="ROLE_USER,ROLE_SUPERVISOR" />
<security:user name="erwin" password="12430911a8af075c6f41c6976af22b09"
authorities="ROLE_USER,ROLE_SUPERVISOR" />
<security:user name="jeremy" password="57c6cbff0d421449be820763f03139eb"
authorities="ROLE_USER" />
<security:user name="scott" password="942f2339bf50796de535a384f0d1af3e"
authorities="ROLE_USER" />
</security:user-service>
</security:authentication-provider>]]>
</programlisting>
</sect2>
<sect2 id="flow-security-configuration-web">
<title>web.xml Configuration</title>
<para>
In the <code>web.xml</code> file, a <code>filter</code> is defined to intercept all requests.
This filter will listen for login/logout requests and process them accordingly.
It will also catch <code>AccesDeniedException</code>s and redirect the user to the login page.
</para>
<programlisting language="xml"><![CDATA[
<filter>
<filter-name>springSecurityFilterChain</filter-name>
<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
</filter>
<filter-mapping>
<filter-name>springSecurityFilterChain</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>]]>
</programlisting>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<book xmlns="http://docbook.org/ns/docbook" version="5.0"
xml:id="spring-webflow-reference"
xmlns:xi="http://www.w3.org/2001/XInclude"
xmlns:xlink="http://www.w3.org/1999/xlink">
<bookinfo>
<title>Spring Web Flow Reference Guide</title>
<titleabbrev>Spring Web Flow</titleabbrev>
<productname>Spring Web Flow</productname>
<releaseinfo>Version 2.4.0</releaseinfo>
<pubdate></pubdate>
<authorgroup>
<author>
<firstname>Keith</firstname>
<surname>Donald</surname>
</author>
<author>
<firstname>Erwin</firstname>
<surname>Vervaet</surname>
</author>
<author>
<firstname>Jeremy</firstname>
<surname>Grelle</surname>
</author>
<author>
<firstname>Scott</firstname>
<surname>Andrews</surname>
</author>
<author>
<firstname>Rossen</firstname>
<surname>Stoyanchev</surname>
</author>
</authorgroup>
<legalnotice>
<para>
Copies of this document may be made for your own use and for
distribution to others, provided that you do not charge any
fee for such copies and further provided that each copy
contains this Copyright Notice, whether distributed in print
or electronically.
</para>
</legalnotice>
</bookinfo>
<toc />
<preface id="preface">
<title>Preface</title>
<para>
Many web applications require the same sequence of steps to execute in different contexts.
Often these sequences are merely components of a larger task the user is trying to accomplish.
Such a reusable sequence is called a flow.
</para>
<para>
Consider a typical shopping cart application.
User registration, login, and cart checkout are all examples of flows that can be invoked from several places in this type of application.
</para>
<para>
Spring Web Flow is the module of Spring for implementing flows.
The Web Flow engine plugs into the Spring Web MVC platform and provides declarative flow definition language.
This reference guide shows you how to use and extend Spring Web Flow.
</para>
</preface>
<xi:include href="overview.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="whatsnew.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="defining-flows.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="el.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="views.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="actions.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="flow-managed-persistence.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="flow-security.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="flow-inheritance.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="system-setup.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="spring-mvc.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="spring-js.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="spring-faces.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="portlet.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="testing.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="upgrade-guide.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
<xi:include href="flow-definition-field-mappings.xml" xmlns:xi="http://www.w3.org/2001/XInclude" />
</book>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="introduction">
<title>Introduction</title>
<sect1 id="manual-overview">
<title>What this guide covers</title>
<para>
This guide covers all aspects of Spring Web Flow.
It covers implementing flows in end-user applications and working with the feature set.
It also covers extending the framework and the overall architectural model.
</para>
</sect1>
<sect1 id="system-requirements">
<title>What Web Flow requires to run</title>
<para>
Java 1.5 or higher
</para>
<para>
Spring 3.0 or higher
</para>
</sect1>
<sect1 id="support">
<title>Where to get support</title>
<para>
Professional from-the-source support on Spring Web Flow is available from
<ulink url="http://www.springsource.com">SpringSource</ulink>, the company behind Spring, and
<ulink url="http://www.ervacon.com">Ervacon</ulink>, operated by Web Flow project co-founder Erwin Vervaet
</para>
</sect1>
<sect1 id="development">
<title>Where to follow development</title>
<para>
You can help make Web Flow best serve the needs of the Spring community by interacting with developers
at the <ulink url="http://forum.springframework.org">Spring Community Forums</ulink>.
</para>
<para>
Report bugs and influence the Web Flow project roadmap using the <ulink url="http://jira.springframework.org">Spring Issue Tracker</ulink>.
</para>
<para>
Subscribe to the <ulink url="http://www.springframework.org">Spring Community Portal</ulink> for the latest Spring news and announcements.
</para>
<para>
Visit the <ulink url="http://www.springframework.org/webflow">Web Flow Project Home</ulink> for more resources on the project.
</para>
</sect1>
<sect1 id="jars-mvn-central">
<title>How to access Web Flow artifacts from Maven Central</title>
<para>
Each jar in the Web Flow distribution is available in the <ulink url="http://search.maven.org">Maven Central Repository</ulink>.
This allows you to easily integrate Web Flow into your application if you are already using Maven as the build system for your web development project.
</para>
<para>
To access Web Flow jars from Maven Central, declare the following dependency in your pom (includes transitive dependencies "spring-binding" and "spring-js"):
</para>
<programlisting language="xml"><![CDATA[
<dependency>
<groupId>org.springframework.webflow</groupId>
<artifactId>spring-webflow</artifactId>
<version>x.y.z.RELEASE</version>
</dependency>
]]>
</programlisting>
<para>
If using JavaServer Faces, declare the following dependency in your pom (includes transitive dependencies "spring-binding", "spring-webflow" and "spring-js"):
</para>
<programlisting language="xml"><![CDATA[
<dependency>
<groupId>org.springframework.webflow</groupId>
<artifactId>spring-faces</artifactId>
<version>x.y.z.RELEASE</version>
</dependency>
]]>
</programlisting>
</sect1>
<sect1 id="jars-ivy">
<title>How to access Web Flow artifacts with Ivy</title>
<para>
To access Spring Web Flow jars with Ivy, add the following repositories to your Ivy config:
</para>
<programlisting language="xml"><![CDATA[
<url name="com.springsource.repository.bundles.release">
<ivy pattern="http://repository.springsource.com/ivy/bundles/release/
[organisation]/[module]/[revision]/[artifact]-[revision].[ext]" />
<artifact pattern="http://repository.springsource.com/ivy/bundles/release/
[organisation]/[module]/[revision]/[artifact]-[revision].[ext]" />
</url>
<url name="com.springsource.repository.bundles.external">
<ivy pattern="http://repository.springsource.com/ivy/bundles/external/
[organisation]/[module]/[revision]/[artifact]-[revision].[ext]" />
<artifact pattern="http://repository.springsource.com/ivy/bundles/external/
[organisation]/[module]/[revision]/[artifact]-[revision].[ext]" />
</url>]]>
</programlisting>
<para>
To access Spring Web Flow jars as well as 3rd party dependencies with Ivy, add the following repository to your Ivy config:
</para>
<programlisting language="xml"><![CDATA[
<url name="springsource-repository">
<ivy pattern="http://repo.springsource.org/libs-release/[organization]/[module]/[revision]/[type]s/ivy-[revision].xml" />
<artifact pattern="http://repo.springsource.org/libs-release/[organization]/[module]/[revision]/[type]s/[module](-[classifier])-[revision].[ext]" />
</url>]]>
</programlisting>
<para>
Then declare the following dependencies in your ivy.xml:
</para>
<programlisting language="xml"><![CDATA[
<dependency org="org.springframework.webflow" name="org.springframework.binding"
rev="x.y.z.RELEASE" conf="compile->runtime" />
<dependency org="org.springframework.webflow" name="org.springframework.js"
rev="x.y.z.RELEASE" conf="compile->runtime" />
<dependency org="org.springframework.webflow" name="org.springframework.webflow"
rev="x.y.z.RELEASE" conf="compile->runtime" />]]>
</programlisting>
<para>
If using JavaServer Faces, declare the following dependency in your pom (also adds the above dependencies):
</para>
<programlisting language="xml"><![CDATA[
<dependency org="org.springframework.webflow" name="org.springframework.faces"
rev="x.y.z.RELEASE" conf="compile->runtime" />]]>
</programlisting>
</sect1>
<sect1>
<title>How to access nightly builds and milestone releases</title>
<para>
Nightly snapshots of Web Flow development branches are available using Maven.
These snapshot builds are useful for testing out fixes you depend on in advance of the next release, and provide a convenient way for you to provide feedback about whether a fix meets your needs.
</para>
<sect2>
<title>Accessing snapshots and milestones with Maven</title>
<para>
For milestones and snapshots you'll need to use the SpringSource repository.
Add the following repository to your Maven pom.xml:
</para>
<programlisting language="xml"><![CDATA[
<repository>
<id>springsource-repository</id>
<name>Spring project snapshots, milestones, and releases</name>
<url>http://repo.springsource.org/snapshot</url>
</repository>]]>
</programlisting>
<para>
Then declare the following dependencies:
</para>
<programlisting language="xml"><![CDATA[
<dependency>
<groupId>org.springframework.webflow</groupId>
<artifactId>spring-binding</artifactId>
<version>x.y.z.BUILD-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>org.springframework.webflow</groupId>
<artifactId>spring-js</artifactId>
<version>x.y.z.BUILD-SNAPSHOT</version>
</dependency>
<dependency>
<groupId>org.springframework.webflow</groupId>
<artifactId>spring-webflow</artifactId>
<version>x.y.z.BUILD-SNAPSHOT</version>
</dependency>]]>
</programlisting>
<para>
And if using JavaServerFaces:
</para>
<programlisting language="xml"><![CDATA[
<dependency>
<groupId>org.springframework.webflow</groupId>
<artifactId>spring-faces</artifactId>
<version>x.y.z.BUILD-SNAPSHOT</version>
</dependency>]]>
</programlisting>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="portlet">
<title>Portlet Integration</title>
<sect1 id="portlet-introduction">
<title>Introduction</title>
<para>
This chapter shows how to use Web Flow in a Portlet environment.
Spring Web Flow requires Portlet API 2.0 to run with.
The <code>booking-portlet-mvc</code> sample application is a good reference for using Web Flow within a portlet.
This application is a simplified travel site that allows users to search for and book hotel rooms.
</para>
</sect1>
<sect1 id="portlet-config-core">
<title>Configuring web.xml and portlet.xml</title>
<para>
The configuration for a portlet depends on the portlet container used.
The sample applications, included with Web Flow, are both configured to use <ulink url="http://portals.apache.org/pluto/">Apache Pluto</ulink>.
</para>
<para>
In general, the configuration requires adding a servlet mapping in the <code>web.xml</code> file to dispatch request to the portlet container.
</para>
<programlisting language="xml"><![CDATA[
<servlet>
<servlet-name>swf-booking-mvc</servlet-name>
<servlet-class>org.apache.pluto.core.PortletServlet</servlet-class>
<init-param>
<param-name>portlet-name</param-name>
<param-value>swf-booking-mvc</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>swf-booking-mvc</servlet-name>
<url-pattern>/PlutoInvoker/swf-booking-mvc</url-pattern>
</servlet-mapping>
]]></programlisting>
<para>
The <code>portlet.xml</code> configuration is a standard portlet configuration.
The <code>portlet-class</code> needs to be set along with a pair of <code>init-param</code>s.
Setting the <code>expiration-cache</code> to <code>0</code> is recommended to force Web Flow to always render a fresh view.
</para>
<programlisting language="xml"><![CDATA[
<portlet>
...
<portlet-class>org.springframework.web.portlet.DispatcherPortlet</portlet-class>
<init-param>
<name>contextConfigLocation</name>
<value>/WEB-INF/web-application-config.xml</value>
</init-param>
<init-param>
<name>viewRendererUrl</name>
<value>/WEB-INF/servlet/view</value>
</init-param>
<expiration-cache>0</expiration-cache>
...
</portlet>
]]></programlisting>
</sect1>
<sect1 id="portlet-config-spring">
<title>Configuring Spring</title>
<sect2 id="portlet-config-spring-handler">
<title>Flow Handlers</title>
<para>
The only supported mechanism for bridging a portlet request to Web Flow is a <code>FlowHandler</code>.
The <code>PortletFlowController</code> used in Web Flow 1.0 is no longer supported.
</para>
<para>
The flow handler, similar to the servlet flow handler, provides hooks that can:
<itemizedlist>
<listitem>
<para>select the flow to execute</para>
</listitem>
<listitem>
<para>pass input parameters to the flow on initialization</para>
</listitem>
<listitem>
<para>handle the flow execution outcome</para>
</listitem>
<listitem>
<para>handle exceptions</para>
</listitem>
</itemizedlist>
</para>
<para>
The <code>AbstractFlowHandler</code> class is an implementation of <code>FlowHandler</code> that provides default implementations for these hooks.
</para>
<para>
In a portlet environment the targeted flow id can not be inferred from the URL and must be defined explicitly in the handler.
</para>
<programlisting language="java"><![CDATA[
public class ViewFlowHandler extends AbstractFlowHandler {
public String getFlowId() {
return "view";
}
}
]]></programlisting>
</sect2>
<sect2 id="portlet-config-spring-mappings">
<title>Handler Mappings</title>
<para>
Spring Portlet MVC provides a rich set of methods to map portlet requests.
Complete documentation is available in the <ulink url="http://static.springframework.org/spring/docs/current/reference/portlet.html#portlet-handlermapping">Spring Reference Documentation</ulink>.
</para>
<para>
The <code>booking-portlet-mvc</code> sample application uses a <code>PortletModeHandlerMapping</code> to map portlet requests.
The sample application only supports <code>view</code> mode, but support for other portlet modes is available.
Other modes can be added and point to the same flow as <code>view</code> mode, or any other flow.
</para>
<programlisting language="xml"><![CDATA[
<bean id="portletModeHandlerMapping"
class="org.springframework.web.portlet.handler.PortletModeHandlerMapping">
<property name="portletModeMap">
<map>
<entry key="view">
<bean class="org.springframework.webflow.samples.booking.ViewFlowHandler" />
</entry>
</map>
</property>
</bean>
]]></programlisting>
</sect2>
<sect2 id="portlet-config-spring-handler-adapter">
<title>Flow Handler Adapter</title>
<para>
A <code>FlowHandlerAdapter</code> converts the handler mappings to the flow handlers.
The flow executor is required as a constructor argument.
</para>
<programlisting language="xml"><![CDATA[
<bean id="flowHandlerAdapter"
class="org.springframework.webflow.mvc.portlet.FlowHandlerAdapter">
<constructor-arg ref="flowExecutor" />
</bean>
]]></programlisting>
</sect2>
</sect1>
<sect1 id="portlet-views">
<title>Portlet Views</title>
<para>
In order to facilitate view rendering, a <code>ViewRendererServlet</code> must be added to the <code>web.xml</code> file.
This servlet is not invoked directly, but it used by Web Flow to render views in a portlet environment.
</para>
<programlisting language="xml"><![CDATA[
<servlet>
<servlet-name>ViewRendererServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.ViewRendererServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ViewRendererServlet</servlet-name>
<url-pattern>/WEB-INF/servlet/view</url-pattern>
</servlet-mapping>
]]></programlisting>
</sect1>
<sect1 id="portlet-modes">
<title>Portlet Modes and Window States</title>
<sect2 id="portlet-modes-state">
<title>Window State</title>
<para>
The Portlet API defined three window states: normal, minimized and maximized.
The portlet implementation must decide what to render for each of these window states.
Web Flow exposes the string value of the window state under <code>portletWindowState</code> via the request map on the external context.
</para>
<programlisting language="java"><![CDATA[
requestContext.getExternalContext().getRequestMap().get("portletWindowState");
]]></programlisting>
<programlisting><![CDATA[
externalContext.requestMap.portletWindowState
]]></programlisting>
</sect2>
<sect2 id="portlet-modes-mode">
<title>Portlet Mode</title>
<para>
The Portlet API defined three portlet modes: view, edit and help.
The portlet implementation must decide what to render for each of these modes.
Web Flow exposes the string value of the portlet mode under <code>portletMode</code> via the request map on the external context.
</para>
<programlisting language="java"><![CDATA[
requestContext.getExternalContext().getRequestMap().get("portletMode");
]]></programlisting>
<programlisting><![CDATA[
externalContext.requestMap.portletMode
]]></programlisting>
</sect2>
</sect1>
<sect1 id="portlet-jsf">
<title>Using Portlets with JSF</title>
<sect2 id="portlet-jsf-using-portlet-jsf">
<para>
Prior to version 2.1 of Spring Web Flow, support for JSF Portlets was considered
experimental and relied on a Portlet Bridge for JSF implementation.
Furthermore JSR-329 (the latest specification in this area), which targets
Portlet API 2.0 and JSF 1.2 environments at the time of writing is not yet
final causing portlet bridge implementations to also remain incomplete.
</para>
<para>
A closer comparison of Spring Web Flow and a Portlet Bridge for JSF shows
the two have significant overlap. They both drive the
JSF lifecycle and they both shield JSF from knowledge about Portlet action
and render requests.
</para>
<para>
Considering all of the above, starting with version 2.2, Spring Web Flow
provides support for JSF Portlets using its own internal Portlet integration rather
than a Portlet Bridge for JSF. We believe this will provide value for Web Flow users
by reducing the number of dependencies in what is already a fairly complex
combination of technologies with specifications lagging behind.
</para>
<para>
What this practically means is the configuration required for JSF Portlets is
very similar to what is alread documented in the rest of this chapter
with the exception of <xref linkend="portlet-views"/>, which is not necessary
with JSF.
</para>
<para>
Review the <code>swf-booking-portlet-faces</code> sample in the Web Flow distribution
for a working JSF Portlets example with complete configuration details. The main thing
you'll need to notice in addition to what has already been described in this
chapter is the <code>faces-config.xml</code> configuration:
</para>
<programlisting language="java"><![CDATA[<?xml version="1.0"?>
<!DOCTYPE faces-config PUBLIC
"-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.0//EN"
"http://java.sun.com/dtd/web-facesconfig_1_0.dtd">
<faces-config>
<application>
<view-handler>
org.springframework.faces.webflow.application.portlet.PortletFaceletViewHandler
</view-handler>
</application>
</faces-config>
]]></programlisting>
</sect2>
</sect1>
<sect1 id="portlet-issues">
<title>Issues in a Portlet Environment</title>
<sect2 id="portlet-issues-redirects">
<title>Redirects</title>
<para>
The Portlet API only allows redirects to be requested from an action request.
Because views are rendered on the render request, views and <code>view-state</code>s cannot trigger a redirect.
</para>
<para>
The <code>externalRedirect:</code> view prefix is a convenience for Servlet based flows.
An <code>IllegalStateException</code> is thrown if a redirect is requested from a render request.
</para>
<para>
<code>end-state</code> redirects can be achieved by implementing <code>FlowHandler.handleExecutionOutcome</code>.
This callback provides the <code>ActionResponse</code> object which supports redirects.
</para>
</sect2>
<sect2 id="portlet-issues-modes">
<title>Switching Portlet Modes</title>
<para>
The portlet container passes the execution key from the previous flow when switching to a new mode.
Even if the mode is mapped to a different <code>FlowHandler</code> the flow execution will resume the previous execution.
You may switch the mode programatically in your FlowHandler after ending a flow in an ActionRequest.
</para>
<para>
One way to start a new flow is to create a URL targeting the mode without the execution key.
</para>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="spring-js">
<title>Spring JavaScript Quick Reference</title>
<sect1 id="spring-js-introduction">
<title>Introduction</title>
<para>
Spring Javascript (spring-js) is a lightweight abstraction over common JavaScript toolkits such as Dojo.
It aims to provide a common client-side programming model for progressively enhancing a web page with rich widget behavior and Ajax remoting.
</para>
<para>
Use of the Spring JS API is demonstrated in the the Spring MVC + Web Flow version of the Spring Travel reference application.
In addition, the JSF components provided as part of the Spring Faces library build on Spring.js.
</para>
</sect1>
<sect1 id="spring-js-resource-servlet">
<title>Serving Javascript Resources</title>
<para>
Spring JS provides a generic <code>ResourceServlet</code> to serve web resources such as JavaScript and CSS files from jar files,
as well as the webapp root directory.
This servlet provides a convenient way to serve Spring.js files to your pages.
To deploy this servlet, declare the following in <code>web.xml</code>:
</para>
<programlisting language="xml"><![CDATA[
<!-- Serves static resource content from .jar files such as spring-js.jar -->
<servlet>
<servlet-name>Resource Servlet</servlet-name>
<servlet-class>org.springframework.js.resource.ResourceServlet</servlet-class>
</servlet>
<!-- Map all /resources requests to the Resource Servlet for handling -->
<servlet-mapping>
<servlet-name>Resource Servlet</servlet-name>
<url-pattern>/resources/*</url-pattern>
</servlet-mapping>]]>
</programlisting>
<para>
Note that starting with version 3.0.4, the Spring Framework includes
a replacement for the <code>ResourceServlet</code> (see the
<ulink url="http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/mvc.html#mvc-static-resources">Spring Framework documentation</ulink>).
With the new &lt;mvc:resources&gt; element resource requests (.js, .css) are handled by the
<code>DispatcherSevlet</code> without the need for a separate <code>ResourceServlet</code>.
Here is the relevant portion of the Spring MVC configuration in
the mvc-booking sample:
</para>
<programlisting language="xml"><![CDATA[
<?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:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<mvc:annotation-driven/>
<mvc:resources mapping="/resources/**" location="/, classpath:/META-INF/web-resources/" />
...
</beans>
]]>
</programlisting>
<para>
This incoming maps requests for <code>/resources</code> to resources found under
<code>/META-INF/web-resources</code> on the classpath. That's where Spring JavaScript resources
are bundled. However, you can modify the location attribute in the above configuration in order
to serve resources from any classpath or web application relative location.
</para>
<para>
Note that the full resource URL depends on how your DispatcherServlet is mapped.
In the mvc-booking sample we've chosen to map it with the default servlet mapping '/':
</para>
<programlisting language="xml"><![CDATA[
<servlet>
<servlet-name>Spring MVC Dispatcher Servlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Spring MVC Dispatcher Servlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
]]>
</programlisting>
<para>
That means the full URL to load <code>Spring.js</code> is <code>/myapp/resources/spring/Spring.js</code>.
If your <code>DispatcherServlet</code> was instead mapped to <code>/main/*</code> then the full
URL would be <code>/myapp/main/resources/spring/Spring.js</code>.
</para>
<para>
When using of the default servlet mapping it is also recommended to add this to your Spring MVC
configuration, which ensures that any resource requests not handled by your Spring MVC mappings
will be delegated back to the Servlet container.
</para>
<programlisting language="xml"><![CDATA[
<?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:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
...
<mvc:default-servlet-handler />
</beans>
]]>
</programlisting>
</sect1>
<sect1 id="spring-js-includes">
<title>Including Spring Javascript in a Page</title>
<para>
Spring JS is designed such that an implementation of its API can be built for any of the popular Javascript toolkits.
The initial implementation of Spring.js builds on the Dojo toolkit.
</para>
<para>
Using Spring Javascript in a page requires including the underlying toolkit as normal,
the <code>Spring.js</code> base interface file, and the <code>Spring-(library implementation).js</code> file for the underlying toolkit.
As an example, the following includes obtain the Dojo implementation of Spring.js using the <code>ResourceServlet</code>:
</para>
<programlisting language="xml"><![CDATA[
<script type="text/javascript" src="<c:url value="/resources/dojo/dojo.js" />"> </script>
<script type="text/javascript" src="<c:url value="/resources/spring/Spring.js" />"> </script>
<script type="text/javascript" src="<c:url value="/resources/spring/Spring-Dojo.js" />"> </script>]]>
</programlisting>
<para>
When using the widget system of an underlying library, typically you must also include some CSS resources to obtain the desired look and feel.
For the booking-mvc reference application, Dojo's <code>tundra.css</code> is included:
</para>
<programlisting language="xml"><![CDATA[
<link type="text/css" rel="stylesheet" href="<c:url value="/resources/dijit/themes/tundra/tundra.css" />" />]]>
</programlisting>
</sect1>
<sect1 id="spring-js-decorations">
<title>Spring Javascript Decorations</title>
<para>
A central concept in Spring Javascript is the notion of applying decorations to existing DOM nodes.
This technique is used to progressively enhance a web page such that the page will still be functional in a less capable browser.
The <code>addDecoration</code> method is used to apply decorations.
</para>
<para>
The following example illustrates enhancing a Spring MVC <code>&lt;form:input&gt;</code> tag with rich suggestion behavior:
</para>
<programlisting language="xml"><![CDATA[
<form:input id="searchString" path="searchString"/>
<script type="text/javascript">
Spring.addDecoration(new Spring.ElementDecoration({
elementId: "searchString",
widgetType: "dijit.form.ValidationTextBox",
widgetAttrs: { promptMessage : "Search hotels by name, address, city, or zip." }}));
</script>]]>
</programlisting>
<para>
The <code>ElementDecoration</code> is used to apply rich widget behavior to an existing DOM node.
This decoration type does not aim to completely hide the underlying toolkit, so the toolkit's native widget type and attributes are used directly.
This approach allows you to use a common decoration model to integrate any widget from the underlying toolkit in a consistent manner.
See the <code>booking-mvc</code> reference application for more examples of applying decorations to do things from suggestions to client-side validation.
</para>
<para>
When using the <code>ElementDecoration</code> to apply widgets that have rich validation behavior, a common need is to prevent the form from being submitted to the server until validation passes.
This can be done with the <code>ValidateAllDecoration</code>:
</para>
<programlisting language="xml"><![CDATA[
<input type="submit" id="proceed" name="_eventId_proceed" value="Proceed" />
<script type="text/javascript">
Spring.addDecoration(new Spring.ValidateAllDecoration({ elementId:'proceed', event:'onclick' }));
</script>]]>
</programlisting>
<para>
This decorates the "Proceed" button with a special onclick event handler that fires the client side validators and does not allow the form to submit until they pass successfully.
</para>
<para>
An <code>AjaxEventDecoration</code> applies a client-side event listener that fires a remote Ajax request to the server. It also auto-registers a callback function to link in the response:
</para>
<programlisting language="xml"><![CDATA[
<a id="prevLink" href="search?searchString=${criteria.searchString}&page=${criteria.page - 1}">Previous</a>
<script type="text/javascript">
Spring.addDecoration(new Spring.AjaxEventDecoration({
elementId: "prevLink",
event: "onclick",
params: { fragments: "body" }
}));
</script>]]>
</programlisting>
<para>
This decorates the onclick event of the "Previous Results" link with an Ajax call, passing along a special parameter that specifies the fragment to be re-rendered in the response.
Note that this link would still be fully functional if Javascript was unavailable in the client.
(See <xref linkend="spring-js-ajax"/> for details on how this request is handled on the server.)
</para>
<para>
It is also possible to apply more than one decoration to an element.
The following example shows a button being decorated with Ajax and validate-all submit suppression:
</para>
<programlisting language="xml"><![CDATA[
<input type="submit" id="proceed" name="_eventId_proceed" value="Proceed" />
<script type="text/javascript">
Spring.addDecoration(new Spring.ValidateAllDecoration({elementId:'proceed', event:'onclick'}));
Spring.addDecoration(new Spring.AjaxEventDecoration({elementId:'proceed', event:'onclick',formId:'booking', params:{fragments:'messages'}}));
</script>]]>
</programlisting>
<para>
It is also possible to apply a decoration to multiple elements in a single statement using Dojo's query API.
The following example decorates a set of checkbox elements as Dojo Checkbox widgets:
</para>
<programlisting language="xml"><![CDATA[
<div id="amenities">
<form:checkbox path="amenities" value="OCEAN_VIEW" label="Ocean View" /></li>
<form:checkbox path="amenities" value="LATE_CHECKOUT" label="Late Checkout" /></li>
<form:checkbox path="amenities" value="MINIBAR" label="Minibar" /></li>
<script type="text/javascript">
dojo.query("#amenities input[type='checkbox']").forEach(function(element) {
Spring.addDecoration(new Spring.ElementDecoration({
elementId: element.id,
widgetType : "dijit.form.CheckBox",
widgetAttrs : { checked : element.checked }
}));
});
</script>
</div>]]>
</programlisting>
</sect1>
<sect1 id="spring-js-ajax">
<title>Handling Ajax Requests</title>
<para>
Spring Javascript's client-side Ajax response handling is built upon the notion of receiving "fragments" back from the server.
These fragments are just standard HTML that is meant to replace portions of the existing page.
The key piece needed on the server is a way to determine which pieces of a full response need to be pulled out for partial rendering.
</para>
<para>
In order to be able to render partial fragments of a full response, the full response must be built using a
templating technology that allows the use of composition for constructing the response, and for the member
parts of the composition to be referenced and rendered individually.
Spring Javascript provides some simple Spring MVC extensions that make use of Tiles to achieve this.
The same technique could theoretically be used with any templating system supporting composition.
</para>
<para>
Spring Javascript's Ajax remoting functionality is built upon the notion that the core handling code for an
Ajax request should not differ from a standard browser request, thus no special knowledge of an Ajax request
is needed directly in the code and the same hanlder can be used for both styles of request.
</para>
<sect2 id="custom-ajax-handler">
<title>Providing a Library-Specific AjaxHandler</title>
<para>
The key interface for integrating various Ajax libraries with the Ajax-aware behavior of Web Flow (such as not redirecting for a
partial page update) is <code>org.springframework.js.AjaxHandler</code>. A <code>SpringJavascriptAjaxHandler</code> is configured by default that is able to
detect an Ajax request submitted via the Spring JS client-side API and can respond appropriately in the case where a redirect is required. In
order to integrate a different Ajax library (be it a pure JavaScript library, or a higher-level abstraction such as an Ajax-capable JSF
component library), a custom <code>AjaxHandler</code> can be injected into the <code>FlowHandlerAdapter</code> or <code>FlowController</code>.
</para>
</sect2>
<sect2 id="spring-js-ajax-mvc">
<title>Handling Ajax Requests with Spring MVC Controllers</title>
<para>
In order to handle Ajax requests with Spring MVC controllers, all that is needed is the configuration of
the provided Spring MVC extensions in your Spring application context for rendering the partial response
(note that these extensions require the use of Tiles for templating):
</para>
<programlisting language="xml"><![CDATA[
<bean id="tilesViewResolver" class="org.springframework.js.ajax.AjaxUrlBasedViewResolver">
<property name="viewClass" value="org.springframework.webflow.mvc.view.FlowAjaxTilesView"/>
</bean>]]>
</programlisting>
<para>
This configures the <code>AjaxUrlBasedViewResolver</code> which in turn interprets Ajax requests and creates <code>FlowAjaxTilesView</code> objects to handle rendering of the appropriate fragments.
Note that <code>FlowAjaxTilesView</code> is capable of handling the rendering for both Web Flow and pure Spring MVC requests.
The fragments correspond to individual attributes of a Tiles view definition. For example, take the following Tiles view definition:
</para>
<programlisting language="xml"><![CDATA[
<definition name="hotels/index" extends="standardLayout">
<put-attribute name="body" value="index.body" />
</definition>
<definition name="index.body" template="/WEB-INF/hotels/index.jsp">
<put-attribute name="hotelSearchForm" value="/WEB-INF/hotels/hotelSearchForm.jsp" />
<put-attribute name="bookingsTable" value="/WEB-INF/hotels/bookingsTable.jsp" />
</definition>]]>
</programlisting>
<para>
An Ajax request could specify the "body", "hotelSearchForm" or "bookingsTable" to be rendered as fragments in the request.
</para>
</sect2>
<sect2 id="spring-js-ajax-mvc-webflow">
<title>Handling Ajax Requests with Spring MVC + Spring Web Flow</title>
<para>
Spring Web Flow handles the optional rendering of fragments directly in the flow definition language through use of the <code>render</code> element.
The benefit of this approach is that the selection of fragments is completely decoupled from client-side code, such that no special parameters need to be passed with the request the way they
currently must be with the pure Spring MVC controller approach.
For example, if you wanted to render the "hotelSearchForm" fragment from the previous example Tiles view into a rich Javascript popup:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="changeSearchCriteria" view="enterSearchCriteria.xhtml" popup="true">
<on-entry>
<render fragments="hotelSearchForm" />
</on-entry>
<transition on="search" to="reviewHotels">
<evaluate expression="searchCriteria.resetPage()"/>
</transition>
</view-state>]]>
</programlisting>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="spring-mvc">
<title>Spring MVC Integration</title>
<sect1 id="spring-mvc-introduction">
<title>Introduction</title>
<para>This chapter shows how to integrate Web Flow into a Spring MVC web
application. The <code>booking-mvc</code> sample application is a good
reference for Spring MVC with Web Flow. This application is a simplified
travel site that allows users to search for and book hotel rooms.</para>
</sect1>
<sect1 id="spring-mvc-config-web.xml">
<title>Configuring web.xml</title>
<para>The first step to using Spring MVC is to configure the
<code>DispatcherServlet</code> in <code>web.xml</code>. You typically do
this once per web application.</para>
<para>The example below maps all requests that begin with
<code>/spring/</code> to the DispatcherServlet. An <code>init-param</code>
is used to provide the <code>contextConfigLocation</code>. This is the
configuration file for the web application.</para>
<programlisting language="xml">
&lt;servlet&gt;
&lt;servlet-name&gt;Spring MVC Dispatcher Servlet&lt;/servlet-name&gt;
&lt;servlet-class&gt;org.springframework.web.servlet.DispatcherServlet&lt;/servlet-class&gt;
&lt;init-param&gt;
&lt;param-name&gt;contextConfigLocation&lt;/param-name&gt;
&lt;param-value&gt;/WEB-INF/web-application-config.xml&lt;/param-value&gt;
&lt;/init-param&gt;
&lt;/servlet&gt;
&lt;servlet-mapping&gt;
&lt;servlet-name&gt;Spring MVC Dispatcher Servlet&lt;/servlet-name&gt;
&lt;url-pattern&gt;/spring/*&lt;/url-pattern&gt;
&lt;/servlet-mapping&gt;</programlisting>
</sect1>
<sect1 id="spring-mvc-config-spring-url-mapping">
<title>Dispatching to flows</title>
<para>The <code>DispatcherServlet</code> maps requests for application
resources to handlers. A flow is one type of handler.</para>
<sect2>
<title>Registering the FlowHandlerAdapter</title>
<para>The first step to dispatching requests to flows is to enable flow
handling within Spring MVC. To this, install the
<code>FlowHandlerAdapter</code>:</para>
<programlisting language="xml">
&lt;!-- Enables FlowHandler URL mapping --&gt;
&lt;bean class="org.springframework.webflow.mvc.servlet.FlowHandlerAdapter"&gt;
&lt;property name="flowExecutor" ref="flowExecutor" /&gt;
&lt;/bean&gt;
</programlisting>
</sect2>
<sect2>
<title>Defining flow mappings</title>
<para>Once flow handling is enabled, the next step is to map specific
application resources to your flows. The simplest way to do this is to
define a <code>FlowHandlerMapping</code>:</para>
<programlisting language="xml">
&lt;!-- Maps request paths to flows in the flowRegistry;
e.g. a path of /hotels/booking looks for a flow with id "hotels/booking" --&gt;
&lt;bean class="org.springframework.webflow.mvc.servlet.FlowHandlerMapping"&gt;
&lt;property name="flowRegistry" ref="flowRegistry"/&gt;
&lt;property name="order" value="0"/&gt;
&lt;/bean&gt;
</programlisting>
<para>Configuring this mapping allows the Dispatcher to map application
resource paths to flows in a flow registry. For example, accessing the
resource path <code>/hotels/booking</code> would result in a registry
query for the flow with id <code>hotels/booking</code>. If a flow is
found with that id, that flow will handle the request. If no flow is
found, the next handler mapping in the Dispatcher's ordered chain will
be queried or a "noHandlerFound" response will be returned.</para>
</sect2>
<sect2>
<title>Flow handling workflow</title>
<para>When a valid flow mapping is found, the
<code>FlowHandlerAdapter</code> figures out whether to start a new
execution of that flow or resume an existing execution based on
information present the HTTP request. There are a number of defaults
related to starting and resuming flow executions the adapter
employs:</para>
<itemizedlist>
<listitem>
<para>HTTP request parameters are made available in the input map of
all starting flow executions.</para>
</listitem>
<listitem>
<para>When a flow execution ends without sending a final response,
the default handler will attempt to start a new execution in the
same request.</para>
</listitem>
<listitem>
<para>Unhandled exceptions are propagated to the Dispatcher unless
the exception is a NoSuchFlowExecutionException. The default handler
will attempt to recover from a NoSuchFlowExecutionException by
starting over a new execution.</para>
</listitem>
</itemizedlist>
<para>Consult the API documentation for <code>FlowHandlerAdapter</code>
for more information. You may override these defaults by subclassing or
by implementing your own FlowHandler, discussed in the next
section.</para>
</sect2>
</sect1>
<sect1 id="spring-mvc-config-flow-handlers">
<title>Implementing custom FlowHandlers</title>
<para><code>FlowHandler</code> is the extension point that can be used to
customize how flows are executed in a HTTP servlet environment. A
<code>FlowHandler</code> is used by the <code>FlowHandlerAdapter</code>
and is responsible for:</para>
<itemizedlist>
<listitem>
<para>Returning the <code>id</code> of a flow definition to
execute</para>
</listitem>
<listitem>
<para>Creating the input to pass new executions of that flow as they
are started</para>
</listitem>
<listitem>
<para>Handling outcomes returned by executions of that flow as they
end</para>
</listitem>
<listitem>
<para>Handling any exceptions thrown by executions of that flow as
they occur</para>
</listitem>
</itemizedlist>
<para>These responsibilities are illustrated in the definition of the
<code>org.springframework.mvc.servlet.FlowHandler</code> interface:</para>
<programlisting language="java">
public interface FlowHandler {
public String getFlowId();
public MutableAttributeMap createExecutionInputMap(HttpServletRequest request);
public String handleExecutionOutcome(FlowExecutionOutcome outcome,
HttpServletRequest request, HttpServletResponse response);
public String handleException(FlowException e,
HttpServletRequest request, HttpServletResponse response);
}
</programlisting>
<para>To implement a FlowHandler, subclass
<code>AbstractFlowHandler</code>. All these operations are optional, and
if not implemented the defaults will apply. You only need to override the
methods that you need. Specifically:</para>
<itemizedlist>
<listitem>
<para>Override <code>getFlowId(HttpServletRequest)</code> when the id
of your flow cannot be directly derived from the HTTP request. By
default, the id of the flow to execute is derived from the pathInfo
portion of the request URI. For example,
<code>http://localhost/app/hotels/booking?hotelId=1</code> results in
a flow id of <code>hotels/booking</code> by default.</para>
</listitem>
<listitem>
<para>Override
<code>createExecutionInputMap(HttpServletRequest)</code> when you need
fine-grained control over extracting flow input parameters from the
HttpServletRequest. By default, all request parameters are treated as
flow input parameters.</para>
</listitem>
<listitem>
<para>Override <code>handleExecutionOutcome</code> when you need to
handle specific flow execution outcomes in a custom manner. The
default behavior sends a redirect to the ended flow's URL to restart a
new execution of the flow.</para>
</listitem>
<listitem>
<para>Override <code>handleException</code> when you need fine-grained
control over unhandled flow exceptions. The default behavior attempts
to restart the flow when a client attempts to access an ended or
expired flow execution. Any other exception is rethrown to the Spring
MVC ExceptionResolver infrastructure by default.</para>
</listitem>
</itemizedlist>
<sect2 id="spring-mvc-flow-handler-example">
<title>Example FlowHandler</title>
<para>A common interaction pattern between Spring MVC And Web Flow is
for a Flow to redirect to a @Controller when it ends. FlowHandlers allow
this to be done without coupling the flow definition itself with a
specific controller URL. An example FlowHandler that redirects to a
Spring MVC Controller is shown below:</para>
<programlisting language="java">
public class BookingFlowHandler extends AbstractFlowHandler {
public String handleExecutionOutcome(FlowExecutionOutcome outcome,
HttpServletRequest request, HttpServletResponse response) {
if (outcome.getId().equals("bookingConfirmed")) {
return "/booking/show?bookingId=" + outcome.getOutput().get("bookingId");
} else {
return "/hotels/index";
}
}
}
</programlisting>
<para>Since this handler only needs to handle flow execution outcomes in
a custom manner, nothing else is overridden. The
<code>bookingConfirmed</code> outcome will result in a redirect to show
the new booking. Any other outcome will redirect back to the hotels
index page.</para>
</sect2>
<sect2>
<title>Deploying a custom FlowHandler</title>
<para>To install a custom FlowHandler, simply deploy it as a bean. The
bean name must match the id of the flow the handler should apply
to.</para>
<programlisting language="xml">
&lt;bean name="hotels/booking" class="org.springframework.webflow.samples.booking.BookingFlowHandler" /&gt;
</programlisting>
<para>With this configuration, accessing the resource
<code>/hotels/booking</code> will launch the <code>hotels/booking</code>
flow using the custom BookingFlowHandler. When the booking flow ends,
the FlowHandler will process the flow execution outcome and redirect to
the appropriate controller.</para>
</sect2>
<sect2 id="spring-mvc-flow-handler-redirects">
<title>FlowHandler Redirects</title>
<para>A FlowHandler handling a FlowExecutionOutcome or FlowException
returns a <code>String</code> to indicate the resource to redirect to
after handling. In the previous example, the
<code>BookingFlowHandler</code> redirects to the
<code>booking/show</code> resource URI for <code>bookingConfirmed</code>
outcomes, and the <code>hotels/index</code> resource URI for all other
outcomes.</para>
<para>By default, returned resource locations are relative to the
current servlet mapping. This allows for a flow handler to redirect to
other Controllers in the application using relative paths. In addition,
explicit redirect prefixes are supported for cases where more control is
needed.</para>
<para>The explicit redirect prefixes supported are:</para>
<itemizedlist>
<listitem>
<para><code>servletRelative:</code> - redirect to a resource
relative to the current servlet</para>
</listitem>
<listitem>
<para><code>contextRelative:</code> - redirect to a resource
relative to the current web application context path</para>
</listitem>
<listitem>
<para><code>serverRelative:</code> - redirect to a resource relative
to the server root</para>
</listitem>
<listitem>
<para><code>http://</code> or <code>https://</code> - redirect to a
fully-qualified resource URI</para>
</listitem>
</itemizedlist>
<para>These same redirect prefixes are also supported within a flow
definition when using the <code>externalRedirect:</code> directive in
conjunction with a view-state or end-state; for example,
<code>view="externalRedirect:http://springframework.org"</code></para>
</sect2>
</sect1>
<sect1 id="spring-mvc-config-spring-view-resolution">
<title>View Resolution</title>
<para>Web Flow 2 maps selected view identifiers to files located within
the flow's working directory unless otherwise specified. For existing
Spring MVC + Web Flow applications, an external <code>ViewResolver</code>
is likely already handling this mapping for you. Therefore, to continue
using that resolver and to avoid having to change how your existing flow
views are packaged, configure Web Flow as follows:</para>
<programlisting language="xml">
&lt;webflow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices"&gt;
&lt;webflow:location path="/WEB-INF/hotels/booking/booking.xml" /&gt;
&lt;/webflow:flow-registry&gt;
&lt;webflow:flow-builder-services id="flowBuilderServices" view-factory-creator="mvcViewFactoryCreator"/&gt;
&lt;bean id="mvcViewFactoryCreator" class="org.springframework.webflow.mvc.builder.MvcViewFactoryCreator"&gt;
&lt;property name="viewResolvers" ref="myExistingViewResolverToUseForFlows"/&gt;
&lt;/bean&gt;
</programlisting>
<para>The MvcViewFactoryCreator is the factory that allows you to
configure how the Spring MVC view system is used inside Spring Web Flow.
Use it to configure existing ViewResolvers, as well as other services such
as a custom MessageCodesResolver. You may also enable data binding use
Spring MVC's native BeanWrapper by setting the
<code>useSpringBinding</code> flag to true. This is an alternative to
using OGNL or the Unified EL for view-to-model data binding. See the
JavaDoc API of this class for more information.</para>
</sect1>
<sect1 id="spring-mvc-resuming-on-event">
<title>Signaling an event from a View</title>
<para>When a flow enters a view-state it pauses, redirects the user to its
execution URL, and waits for a user event to resume. Events are generally
signaled by activating buttons, links, or other user interface commands.
How events are decoded server-side is specific to the view technology in
use. This section shows how to trigger events from HTML-based views
generated by templating engines such as JSP, Velocity, or
Freemarker.</para>
<sect2 id="webflow-event-named-html-button">
<title>Using a named HTML button to signal an event</title>
<para>The example below shows two buttons on the same form that signal
<code>proceed</code> and <code>cancel</code> events when clicked,
respectively.</para>
<programlisting language="xml">
&lt;input type="submit" name="_eventId_proceed" value="Proceed" /&gt;
&lt;input type="submit" name="_eventId_cancel" value="Cancel" /&gt;
</programlisting>
<para>When a button is pressed Web Flow finds a request parameter name
beginning with <code>_eventId_</code> and treats the remaining substring
as the event id. So in this example, submitting
<code>_eventId_proceed</code> becomes <code>proceed</code>. This style
should be considered when there are several different events that can be
signaled from the same form.</para>
</sect2>
<sect2 id="webflow-event-hidden-parameter">
<title>Using a hidden HTML form parameter to signal an event</title>
<para>The example below shows a form that signals the
<code>proceed</code> event when submitted:</para>
<programlisting language="xml">
&lt;input type="submit" value="Proceed" /&gt;
&lt;input type="hidden" name="_eventId" value="proceed" /&gt;
</programlisting>
<para>Here, Web Flow simply detects the special <code>_eventId</code>
parameter and uses its value as the event id. This style should only be
considered when there is one event that can be signaled on the
form.</para>
</sect2>
<sect2 id="webflow-event-link">
<title>Using a HTML link to signal an event</title>
<para>The example below shows a link that signals the
<code>cancel</code> event when activated:</para>
<programlisting language="xml">
&lt;a href="${flowExecutionUrl}&amp;_eventId=cancel"&gt;Cancel&lt;/a&gt;
</programlisting>
<para>Firing an event results in a HTTP request being sent back to the
server. On the server-side, the flow handles decoding the event from
within its current view-state. How this decoding process works is
specific to the view implementation. Recall a Spring MVC view
implementation simply looks for a request parameter named
<code>_eventId</code>. If no <code>_eventId</code> parameter is found,
the view will look for a parameter that starts with
<code>_eventId_</code> and will use the remaining substring as the event
id. If neither cases exist, no flow event is triggered.</para>
</sect2>
</sect1>
<sect1 id="spring-mvc-embedded-flow">
<title>Embedding A Flow On A Page</title>
<para>By default when a flow enters a view state, it executes a
client-side redirect before rendering the view. This approach is known as
POST-REDIRECT-GET. It has the advantage of separating the form processing
for one view from the rendering of the next view. As a result the browser
Back and Refresh buttons work seamlessly without causing any browser
warnings.</para>
<para>Normally the client-side redirect is transparent from a user's
perspective. However, there are situations where POST-REDIRECT-GET may not
bring the same benefits. For example a flow may be embedded on a page and driven via
Ajax requests refreshing only the area of the page that belongs to the flow.
Not only is it unnecessary to use client-side redirects in this case, it
is also not the desired behavior with regards to keeping the surrounding
content of the page intact.</para>
<para>The <xref linkend="spring-js-ajax" /> explains how to do
partial rendering during Ajax requests. The focus of this section is to
explain how to control flow execution redirect behavior during
Ajax requests. To indicate a flow should execute in "page embedded" mode all
you need to do is append an extra parameter when launching the
flow:</para>
<programlisting language="xml">/hotels/booking?mode=embedded</programlisting>
<para>When launched in "page embedded" mode a flow will not issue
flow execution redirects during Ajax requests. The mode=embedded parameter
only needs to be passed when launching the flow. Your only other concern is
to use Ajax requests and to render only the content required to update
the portion of the page displaying the flow.</para>
<sect2 id="spring-mvc-embedded-flow-alternatives">
<title>Embedded Mode Vs Default Redirect Behavior</title>
<para>
By default Web Flow does a client-side redirect upon entering every view state.
However if you remain in the same view state -- for example a transition without a "to" attribute -- during an Ajax request there will not be a client-side redirect.
This behavior should be quite familiar to Spring Web Flow 2 users.
It is appropriate for a top-level flow that supports the browser back button while still taking advantage of Ajax and partial rendering for use cases where you remain in the same view such as form validation, paging trough search results, and others.
However transitions to a new view state are always followed with a client-side redirect.
That makes it impossible to embed a flow on a page or within a modal dialog and execute more than one view state without causing a full-page refresh.
Hence if your use case requires embedding a flow you can launch it in "embedded" mode.
</para>
</sect2>
<sect2 id="spring-mvc-embedded-flow-examples">
<title>Embedded Flow Examples</title>
<para>If you'd like to see examples of a flow embedded on a page and within
a modal dialog please refer to the webflow-showcase project. You can check out
the source code locally, build it as you would a Maven project, and import
it into Eclipse:</para>
<para><programlisting language="xml">cd some-directory
svn co https://src.springframework.org/svn/spring-samples/webflow-showcase
cd webflow-showcase
mvn package
# import into Eclipse</programlisting>
</para>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="system-setup">
<title>System Setup</title>
<sect1 id="system-setup-introduction">
<title>Introduction</title>
<para>
This chapter shows you how to setup the Web Flow system for use in any web environment.
</para>
</sect1>
<sect1 id="system-config-schema">
<title>webflow-config.xsd</title>
<para>
Web Flow provides a Spring schema that allows you to configure the system.
To use this schema, include it in one of your infrastructure-layer beans files:
</para>
<programlisting language="xml"><![CDATA[
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:webflow="http://www.springframework.org/schema/webflow-config"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/webflow-config
http://www.springframework.org/schema/webflow-config/spring-webflow-config-2.3.xsd">
<!-- Setup Web Flow here -->
</beans>]]>
</programlisting>
</sect1>
<sect1 id="system-config-basic">
<title>Basic system configuration</title>
<para>
The next section shows the minimal configuration required to set up the Web Flow system in your application.
</para>
<sect2 id="basic-setup-flow-registry">
<title>FlowRegistry</title>
<para>
Register your flows in a <code>FlowRegistry</code>:
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-registry id="flowRegistry">
<webflow:flow-location path="/WEB-INF/flows/booking/booking.xml" />
</webflow:flow-registry>]]>
</programlisting>
</sect2>
<sect2 id="basic-setup-flow-executor">
<title>FlowExecutor</title>
<para>
Deploy a FlowExecutor, the central service for executing flows:
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-executor id="flowExecutor" />]]>
</programlisting>
<para>
See the Spring MVC and Spring Faces sections of this guide on how to integrate the Web Flow system with the MVC and JSF environment, respectively.
</para>
</sect2>
</sect1>
<sect1 id="flow-registry">
<title>flow-registry options</title>
<para>
This section explores flow-registry configuration options.
</para>
<sect2 id="flow-registry-location">
<title>Specifying flow locations</title>
<para>
Use the <code>location</code> element to specify paths to flow definitions to register.
By default, flows will be assigned registry identifiers equal to their filenames minus the file extension, unless a registry bath path is defined.
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-location path="/WEB-INF/flows/booking/booking.xml" />]]>
</programlisting>
</sect2>
<sect2 id="flow-registry-location-id">
<title>Assigning custom flow identifiers</title>
<para>
Specify an id to assign a custom registry identifier to a flow:
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-location path="/WEB-INF/flows/booking/booking.xml" id="bookHotel" />]]>
</programlisting>
</sect2>
<sect2 id="flow-registry-location-attributes">
<title>Assigning flow meta-attributes</title>
<para>
Use the <code>flow-definition-attributes</code> element to assign custom meta-attributes to a registered flow:
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-location path="/WEB-INF/flows/booking/booking.xml">
<webflow:flow-definition-attributes>
<webflow:attribute name="caption" value="Books a hotel" />
</webflow:flow-definition-attributes>
</webflow:flow-location>]]>
</programlisting>
</sect2>
<sect2 id="flow-registry-patterns">
<title>Registering flows using a location pattern</title>
<para>
Use the <code>flow-location-patterns</code> element to register flows that match a specific resource location pattern:
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-location-pattern value="/WEB-INF/flows/**/*-flow.xml" />]]>
</programlisting>
</sect2>
<sect2 id="flow-registry-base-path">
<title>Flow location base path</title>
<para>
Use the <code>base-path</code> attribute to define a base location for all flows in the application.
All flow locations are then relative to the base path.
The base path can be a resource path such as '/WEB-INF' or a location on the classpath like 'classpath:org/springframework/webflow/samples'.
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-registry id="flowRegistry" base-path="/WEB-INF">
<webflow:flow-location path="/hotels/booking/booking.xml" />
</webflow:flow-registry>]]>
</programlisting>
<para>
With a base path defined, the algorithm that assigns flow identifiers changes slightly.
Flows will now be assigned registry identifiers equal to the the path segment between their base path and file name.
For example, if a flow definition is located at '/WEB-INF/hotels/booking/booking-flow.xml' and the base path is '/WEB-INF' the remaining path to this flow is 'hotels/booking' which becomes the flow id.
</para>
<tip>
<title>Directory per flow definition</title>
<para>
Recall it is a best practice to package each flow definition in a unique directory.
This improves modularity, allowing dependent resources to be packaged with the flow definition.
It also prevents two flows from having the same identifiers when using the convention.
</para>
</tip>
<para>
If no base path is not specified or if the flow definition is directly on the base path, flow id assignment from the filename (minus the extension) is used.
For example, if a flow definition file is 'booking.xml', the flow identifier is simply 'booking'.
</para>
<para>
Location patterns are particularly powerful when combined with a registry base path.
Instead of the flow identifiers becoming '*-flow', they will be based on the directory path.
For example:
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-registry id="flowRegistry" base-path="/WEB-INF">
<webflow:flow-location-pattern value="/**/*-flow.xml" />
</webflow:flow-registry>]]>
</programlisting>
<para>
In the above example, suppose you had flows located in <code>/user/login</code>, <code>/user/registration</code>, <code>/hotels/booking</code>, and <code>/flights/booking</code> directories within <code>WEB-INF</code>,
you'd end up with flow ids of <code>user/login</code>, <code>user/registration</code>, <code>hotels/booking</code>, and <code>flights/booking</code>, respectively.
</para>
</sect2>
<sect2 id="flow-registry-parent">
<title>Configuring FlowRegistry hierarchies</title>
<para>
Use the <code>parent</code> attribute to link two flow registries together in a hierarchy.
When the child registry is queried, if it cannot find the requested flow it will delegate to its parent.
</para>
<programlisting language="xml"><![CDATA[
<!-- my-system-config.xml -->
<webflow:flow-registry id="flowRegistry" parent="sharedFlowRegistry">
<webflow:flow-location path="/WEB-INF/flows/booking/booking.xml" />
</webflow:flow-registry>
<!-- shared-config.xml -->
<webflow:flow-registry id="sharedFlowRegistry">
<!-- Global flows shared by several applications -->
</webflow:flow-registry>]]>
</programlisting>
</sect2>
<sect2 id="flow-registry-builder-services">
<title>Configuring custom FlowBuilder services</title>
<para>
Use the <code>flow-builder-services</code> attribute to customize the services and settings used to build flows in a flow-registry.
If no flow-builder-services tag is specified, the default service implementations are used.
When the tag is defined, you only need to reference the services you want to customize.
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices">
<webflow:flow-location path="/WEB-INF/flows/booking/booking.xml" />
</webflow:flow-registry>
<webflow:flow-builder-services id="flowBuilderServices" />]]>
</programlisting>
<para>
The configurable services are the <code>conversion-service</code>, <code>expression-parser</code>, and <code>view-factory-creator</code>.
These services are configured by referencing custom beans you define. For example:
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-builder-services id="flowBuilderServices"
conversion-service="conversionService"
expression-parser="expressionParser"
view-factory-creator="viewFactoryCreator" />
<bean id="conversionService" class="..." />
<bean id="expressionParser" class="..." />
<bean id="viewFactoryCreator" class="..." />]]>
</programlisting>
<sect3 id="builder-service-conversion">
<title>conversion-service</title>
<para>
Use the <code>conversion-service</code> attribute to customize the <code>ConversionService</code> used by the Web Flow system.
Type conversion is used to convert from one type to another when required during flow execution such as when processing request parameters, invoking actions, and so on.
Many common object types such as numbers, classes, and enums are supported.
However you'll probably need to provide your own type conversion and formatting logic for custom data types.
Please read <xref linkend="view-type-conversion"/> for important information on how to provide custom type conversion logic.
</para>
</sect3>
<sect3 id="builder-service-expression-parser">
<title>expression-parser</title>
<para>
Use the <code>expression-parser</code> attribute to customize the <code>ExpressionParser</code> used by the Web Flow system.
The default ExpressionParser uses the Unified EL if available on the classpath, otherwise OGNL is used.
</para>
</sect3>
<sect3 id="builder-service-view-factory-creator">
<title>view-factory-creator</title>
<para>
Use the <code>view-factory-creator</code> attribute to customize the <code>ViewFactoryCreator</code> used by the Web Flow system.
The default ViewFactoryCreator produces Spring MVC ViewFactories capable of rendering JSP, Velocity, and Freemarker views.
</para>
<para>
The configurable settings are <code>development</code>.
These settings are global configuration attributes that can be applied during the flow construction process.
</para>
</sect3>
<sect3 id="builder-development">
<title>development</title>
<para>
Set this to <code>true</code> to switch on flow <emphasis>development mode</emphasis>.
Development mode switches on hot-reloading of flow definition changes, including changes to dependent flow resources such as message bundles.
</para>
</sect3>
</sect2>
</sect1>
<sect1 id="flow-executor">
<title>flow-executor options</title>
<para>
This section explores flow-executor configuration options.
</para>
<sect2 id="flow-executor-execution-listeners">
<title>Attaching flow execution listeners</title>
<para>
Use the <code>flow-execution-listeners</code> element to register listeners that observe the lifecycle of flow executions:
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-execution-listeners>
<webflow:listener ref="securityListener"/>
<webflow:listener ref="persistenceListener"/>
</webflow:flow-execution-listeners>]]>
</programlisting>
<para>
You may also configure a listener to observe only certain flows:
</para>
<programlisting language="xml"><![CDATA[
<webflow:listener ref="securityListener" criteria="securedFlow1,securedFlow2"/>]]>
</programlisting>
</sect2>
<sect2 id="tuning-flow-execution-repository">
<title>Tuning FlowExecution persistence</title>
<para>
Use the <code>flow-execution-repository</code> element to tune flow execution persistence settings:
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-executor id="flowExecutor" flow-registry="flowRegistry">
<webflow:flow-execution-repository max-executions="5" max-execution-snapshots="30" />
</webflow:flow-executor>]]>
</programlisting>
<sect3 id="repository-max-executions">
<title>max-executions</title>
<para>
Tune the <code>max-executions</code> attribute to place a cap on the number of flow executions that can be created per user session.
When the maximum number of executions is exceeded, the oldest execution is removed.
<note>
<para>
The <code>max-executions</code> attribute is per user session, i.e. it works across instances of any flow definition.
</para>
</note>
</para>
</sect3>
<sect3 id="repository-max-snapshots">
<title>max-execution-snapshots</title>
<para>
Tune the <code>max-execution-snapshots</code> attribute to place a cap on the number of history snapshots that can be taken per flow execution.
To disable snapshotting, set this value to 0. To enable an unlimited number of snapshots, set this value to -1.
<note>
<para>
History snapshots enable browser back button support.
When snapshotting is disabled pressing the browser back button will not work.
It will result in using an execution key that points to a snapshot that has not be recorded.
</para>
</note>
</para>
</sect3>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="testing">
<title>Testing flows</title>
<sect1 id="testing-introduction">
<title>Introduction</title>
<para>
This chapter shows you how to test flows.
</para>
</sect1>
<sect1 id="extending-abstractflowexecutiontest">
<title>Extending AbstractXmlFlowExecutionTests</title>
<para>
To test the execution of a XML-based flow definition, extend <code>AbstractXmlFlowExecutionTests</code>:
</para>
<programlisting language="java"><![CDATA[
public class BookingFlowExecutionTests extends AbstractXmlFlowExecutionTests {
}]]>
</programlisting>
</sect1>
<sect1 id="override-getResource">
<title>Specifying the path to the flow to test</title>
<para>
At a minimum, you must override <code>getResource(FlowDefinitionResourceFactory)</code> to return the path to the flow you wish to test:
</para>
<programlisting language="java"><![CDATA[
@Override
protected FlowDefinitionResource getResource(FlowDefinitionResourceFactory resourceFactory) {
return resourceFactory.createFileResource("src/main/webapp/WEB-INF/hotels/booking/booking.xml");
}]]>
</programlisting>
</sect1>
<sect1 id="override-configureFlowBuilderContext">
<title>Registering flow dependencies</title>
<para>
If your flow has dependencies on externally managed services,
also override <code>configureFlowBuilderContext(MockFlowBuilderContext)</code> to register stubs or mocks of those services:
</para>
<programlisting language="java"><![CDATA[
@Override
protected void configureFlowBuilderContext(MockFlowBuilderContext builderContext) {
builderContext.registerBean("bookingService", new StubBookingService());
}]]>
</programlisting>
<para>
If your flow extends from another flow, or has states that extend other states,
also override <code>getModelResources(FlowDefinitionResourceFactory)</code> to return the path to the parent flows.
</para>
<programlisting language="java"><![CDATA[
@Override
protected FlowDefinitionResource[] getModelResources(FlowDefinitionResourceFactory resourceFactory) {
return new FlowDefinitionResource[] {
resourceFactory.createFileResource("src/main/webapp/WEB-INF/common/common.xml")
};
}]]>
</programlisting>
</sect1>
<sect1 id="testing-flowstartup">
<title>Testing flow startup</title>
<para>
Have your first test exercise the startup of your flow:
</para>
<programlisting language="java"><![CDATA[
public void testStartBookingFlow() {
Booking booking = createTestBooking();
MutableAttributeMap input = new LocalAttributeMap();
input.put("hotelId", "1");
MockExternalContext context = new MockExternalContext();
context.setCurrentUser("keith");
startFlow(input, context);
assertCurrentStateEquals("enterBookingDetails");
assertTrue(getRequiredFlowAttribute("booking") instanceof Booking);
}]]>
</programlisting>
<para>
Assertions generally verify the flow is in the correct state you expect.
</para>
</sect1>
<sect1 id="testing-flowevents">
<title>Testing flow event handling</title>
<para>
Define additional tests to exercise flow event handling behavior.
You goal should be to exercise all paths through the flow.
You can use the convenient <code>setCurrentState(String)</code> method to jump to the flow state where you wish to begin your test.
</para>
<programlisting language="java"><![CDATA[
public void testEnterBookingDetails_Proceed() {
setCurrentState("enterBookingDetails");
getFlowScope().put("booking", createTestBooking());
MockExternalContext context = new MockExternalContext();
context.setEventId("proceed");
resumeFlow(context);
assertCurrentStateEquals("reviewBooking");
}]]>
</programlisting>
</sect1>
<sect1 id="testing-mockingsubflows">
<title>Mocking a subflow</title>
<para>
To test calling a subflow, register a mock implementation of the subflow that asserts input was passed in correctly and
returns the correct outcome for your test scenario.
</para>
<programlisting language="java"><![CDATA[
public void testBookHotel() {
setCurrentState("reviewHotel");
Hotel hotel = new Hotel();
hotel.setId(1L);
hotel.setName("Jameson Inn");
getFlowScope().put("hotel", hotel);
getFlowDefinitionRegistry().registerFlowDefinition(createMockBookingSubflow());
MockExternalContext context = new MockExternalContext();
context.setEventId("book");
resumeFlow(context);
// verify flow ends on 'bookingConfirmed'
assertFlowExecutionEnded();
assertFlowExecutionOutcomeEquals("finish");
}
public Flow createMockBookingSubflow() {
Flow mockBookingFlow = new Flow("booking");
mockBookingFlow.setInputMapper(new Mapper() {
public MappingResults map(Object source, Object target) {
// assert that 1L was passed in as input
assertEquals(1L, ((AttributeMap) source).get("hotelId"));
return null;
}
});
// immediately return the bookingConfirmed outcome so the caller can respond
new EndState(mockBookingFlow, "bookingConfirmed");
return mockBookingFlow;
}]]>
</programlisting>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="upgrade-guide">
<title>Upgrading from 1.0</title>
<sect1 id="upgrade-guide-introduction">
<title>Introduction</title>
<para>
This chapter shows you how to upgrade existing Web Flow 1 application to Web Flow 2.
</para>
</sect1>
<sect1 id="upgrade-guide-definition-language">
<title>Flow Definition Language</title>
<para>
The core concepts behind the flow definition language have not changed between Web Flow 1 and 2.
However, some of the element and attribute names have changed.
These changes allow for the language to be both more concise and expressive.
A complete list of <link linkend="field-mappings">mapping changes</link> is available as an appendix.
</para>
<sect2 id="upgrade-guide-definition-language-tool">
<title>Flow Definition Updater Tool</title>
<para>
An automated tool is available to aid in the conversion of existing 1.x flows to the new 2.x style.
The tool will convert all the old tag names to their new equivalents, if needed.
While the tool will make a best effort attempt at conversion, there is not a one-to-one mapping for all version 1 concepts.
If the tool was unable to convert a portion of the flow, it will be marked with a <code>WARNING</code> comment in the resulting flow.
</para>
<para>
The conversion tool requires spring-webflow.jar, spring-core.jar and an XSLT 1.0 engine.
<ulink url="http://saxon.sourceforge.net/">Saxon 6.5.5</ulink> is recommended.
</para>
<para>
The tool can be run from the command line with the following command.
Required libraries must be available on the classpath.
The source must be a single flow to convert.
The resulting converted flow will be sent to standard output.
</para>
<programlisting>
java org.springframework.webflow.upgrade.WebFlowUpgrader flow-to-upgrade.xml
</programlisting>
<sect3 id="upgrade-guide-definition-language-tool-warnings">
<title>Flow Definition Updater Tool Warnings</title>
<sect4 id="upgrade-guide-definition-language-tool-warnings-argument-parameter-type">
<title>argument parameter-type no longer supported</title>
<para>
Bean actions have been deprecated in favor of EL based evaluate expressions.
The EL expression is able to accept method parameters directly, so there is no longer a need for the argument tag.
A side effect of this change is that method arguments must be of the correct type before invoking the action.
</para>
</sect4>
<sect4 id="upgrade-guide-definition-language-tool-warnings-inline-flow">
<title>inline-flow is no longer supported</title>
<para>
Inline flows are no longer supported.
The contents of the inline flow must be moved into a new top-level flow.
The inline flow's content has been converted for your convenience.
</para>
</sect4>
<sect4 id="upgrade-guide-definition-language-tool-warnings-mapping-target-collection">
<title>mapping target-collection is no longer supported</title>
<para>
Output mappings can no longer add an item to a collection.
Only assignment is supported.
</para>
</sect4>
<sect4 id="upgrade-guide-definition-language-tool-warnings-var-bean">
<title>var bean is no longer supported</title>
<para>
The var bean attribute is no longer needed.
All spring beans can be resolved via EL.
</para>
</sect4>
<sect4 id="upgrade-guide-definition-language-tool-warnings-var-scope">
<title>var scope is no longer supported</title>
<para>
The var element will place all variable into flow scope.
Conversation scope was previously allowed.
</para>
</sect4>
</sect3>
</sect2>
<sect2 id="upgrade-guide-definition-language-el">
<title>EL Expressions</title>
<para>
EL expressions are used heavily throughout the flow definition language.
Many of the attributes that appear to be plain text are actually interpreted as EL.
The standard EL delimiters (either ${} or #{} in Web Flow 2.0 or just #{} in Web Flow 2.1) are not necessary and will often cause an exception if they are included.
</para>
<para>
EL delimiters should be removed where necessary by the updater tool.
</para>
</sect2>
</sect1>
<sect1 id="upgrade-guide-webflow-config">
<title>Web Flow Configuration</title>
<para>
In Web Flow 1 there were two options available for configuring Web Flow, one using standard spring bean XML and the other using the <code>webflow-config-1.0</code> schema.
The schema configuration option simplifies the configuration process by keeping long internal class names hidden and enabling contextual auto-complete.
The schema configuration option is the only way to configure Web Flow 2.
</para>
<sect2 id="upgrade-guide-webflow-config-beans">
<title>Web Flow Bean Configuration</title>
<para>
The <code>FactoryBean</code> bean XML configuration method used in Web Flow 1 is no longer supported.
The schema configuration method should be used instead.
In particular beans defining <code>FlowExecutorFactoryBean</code> and <code>XmlFlowRegistryFactoryBean</code> should be updated.
Continue reading Web Flow Schema Configuration for details.
</para>
</sect2>
<sect2 id="upgrade-guide-webflow-config-schema">
<title>Web Flow Schema Configuration</title>
<para>
The <code>webflow-config</code> configuration schema has also changed slightly from version 1 to 2.
The simplest way to update your application is modify the version of the schema to 2.0 then fix any errors in a schema aware XML editor.
The most common change is add 'flow-' to the beginning of the elements defined by the schema.
</para>
<programlisting language="xml"><![CDATA[
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:webflow="http://www.springframework.org/schema/webflow-config"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/webflow-config
http://www.springframework.org/schema/webflow-config/spring-webflow-config-2.3.xsd">
]]></programlisting>
<sect3 id="upgrade-guide-webflow-config-schema-executor">
<title>flow-executor</title>
<para>
The flow executor is the core Web Flow configuration element.
This element replaces previous <code>FlowExecutorFactoryBean</code> bean definitions.
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-executor id="flowExecutor" />
]]></programlisting>
</sect3>
<sect3 id="upgrade-guide-webflow-config-schema-listeners">
<title>flow-execution-listeners</title>
<para>
Flow execution listeners are also defined in the flow executor.
Listeners are defined using standard bean definitions and added by reference.
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-executor id="flowExecutor" flow-registry="flowRegistry">
<webflow:flow-execution-listeners>
<webflow:listener ref="securityFlowExecutionListener"/>
</webflow:flow-execution-listeners>
</webflow:flow-executor>
<bean id="securityFlowExecutionListener"
class="org.springframework.webflow.security.SecurityFlowExecutionListener" />
]]></programlisting>
</sect3>
<sect3 id="upgrade-guide-webflow-config-schema-registry">
<title>flow-registry</title>
<para>
The <code>flow-registry</code> contains a set of <code>flow-location</code>s.
Every flow definition used by Web Flow must be added to the registry.
This element replaces previous <code>XmlFlowRegistryFactoryBean</code> bean definitions.
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-registry id="flowRegistry">
<webflow:flow-location path="/WEB-INF/hotels/booking/booking.xml" />
</webflow:flow-registry>
]]></programlisting>
</sect3>
</sect2>
<sect2 id="upgrade-guide-java-controller">
<title>Flow Controller</title>
<para>
The package name for flow controllers has changed from <code>org.springframework.webflow.executor.mvc.FlowController</code> and is now <code>org.springframework.webflow.mvc.servlet.FlowController</code> for Servlet MVC requests.
The portlet flow controller <code>org.springframework.webflow.executor.mvc.PortletFlowController</code> has been replaced by a flow handler adapter available at <code>org.springframework.webflow.mvc.portlet.FlowHandlerAdapter</code>.
They will need to be updated in the bean definitions.
</para>
</sect2>
<sect2 id="upgrade-guide-java-url-handler">
<title>Flow URL Handler</title>
<para>
The default URL handler has changed in Web Flow 2.
The flow identifier is now derived from the URL rather then passed explicitly.
In order to maintain comparability with existing views and URL structures a <code>WebFlow1FlowUrlHandler</code> is available.
</para>
<programlisting language="xml"><![CDATA[
<bean name="/pos.htm" class="org.springframework.webflow.mvc.servlet.FlowController">
<property name="flowExecutor" ref="flowExecutor" />
<property name="flowUrlHandler">
<bean class="org.springframework.webflow.context.servlet.WebFlow1FlowUrlHandler" />
</property>
</bean>
]]></programlisting>
</sect2>
<sect2 id="upgrade-guide-webflow-config-view-resolver">
<title>View Resolution</title>
<para>
Web Flow 2 by default will both select and render views.
View were previously selected by Web Flow 1 and then rendered by an external view resolver.
</para>
<para>
In order for version 1 flows to work in Web Flow 2 the default view resolver must be overridden.
A common use case is to use <ulink url="http://tiles.apache.org/">Apache Tiles</ulink> for view resolution.
The following configuration will replace the default view resolver with a Tiles view resolver.
The <code>tilesViewResolver</code> in this example can be replaced with any other view resolver.
</para>
<programlisting language="xml"><![CDATA[
<webflow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices">
<web:flow-location path="..." />
...
</webflow:flow-registry>
<webflow:flow-builder-services id="flowBuilderServices"
view-factory-creator="viewFactoryCreator"/>
<bean id="viewFactoryCreator" class="org.springframework.webflow.mvc.builder.MvcViewFactoryCreator">
<property name="viewResolvers" ref="tilesViewResolver" />
</bean>
<bean id="tilesViewResolver" class="org.springframework.web.servlet.view.UrlBasedViewResolver">
<property name="viewClass" value="org.springframework.web.servlet.view.tiles.TilesJstlView" />
</bean>
<bean class="org.springframework.web.servlet.view.tiles.TilesConfigurer">
<property name="definitions" value="/WEB-INF/tiles-def.xml" />
</bean>
]]></programlisting>
</sect2>
</sect1>
<sect1 id="upgrade-guide-webflow-concepts">
<title>New Web Flow Concepts</title>
<sect2 id="upgrade-guide-webflow-concepts-binding">
<title>Automatic Model Binding</title>
<para>
Web Flow 1 required Spring MVC based flows to manually call <code>FormAction</code> methods, notably:
<code>setupForm</code>, <code>bindAndValidate</code> to process form views.
Web Flow 2 now provides automatic model setup and binding using the <code>model</code> attribute for <code>view-state</code>s.
Please see the <link linkend="view-model">Binding to a Model</link> section for details.
</para>
</sect2>
<sect2 id="upgrade-guide-webflow-concepts-el-v-ognl">
<title>OGNL vs Spring EL</title>
<para>
Web Flow 1 used OGNL exclusively for expressions within the flow definitions.
Web Flow 2 adds support for Unified EL.
Web Flow 2.1 uses Spring EL by default.
United EL and OGNL can still be plugged in.
Please see <xref linkend="el"/> for details.
</para>
</sect2>
<sect2 id="upgrade-guide-webflow-concepts-flash-scope">
<title>Flash Scope</title>
<para>
Flash scope in Web Flow 1 lived across the current request and into the next request.
This was conceptually similar to Web Flow 2's view scope concept, but the semantics were not as well defined.
In Web Flow 2, flash scope is cleared after every view render.
This makes flashScope semantics in Web Flow consistent with other web frameworks.
</para>
</sect2>
<sect2 id="upgrade-guide-webflow-concepts-jsf">
<title>JSF</title>
<para>
Web Flow 2 offers significantly improved integration with JSF.
Please see <xref linkend="spring-faces"/> for details.
</para>
</sect2>
<sect2 id="upgrade-guide-webflow-concepts-redirects">
<title>External Redirects</title>
<para>
External redirects in Web Flow 1 were always considered context relative.
In Web Flow 2, if the redirect URL begins with a slash, it is considered servlet-relative instead of context-relative.
URLs without a leading slash are still context relative.
</para>
</sect2>
</sect1>
</chapter>

854
src/reference/views.xml Normal file
View File

@@ -0,0 +1,854 @@
<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="views">
<title>Rendering views</title>
<sect1 id="views-introduction">
<title>Introduction</title>
<para>
This chapter shows you how to use the <code>view-state</code> element to render views within a flow.
</para>
</sect1>
<sect1 id="view-convention">
<title>Defining view states</title>
<para>
Use the <code>view-state</code> element to define a step of the flow that renders a view and waits for a user event to resume:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails">
<transition on="submit" to="reviewBooking" />
</view-state>]]>
</programlisting>
<para>
By convention, a view-state maps its id to a view template in the directory where the flow is located.
For example, the state above might render <filename>/WEB-INF/hotels/booking/enterBookingDetails.xhtml</filename>
if the flow itself was located in the <filename>/WEB-INF/hotels/booking</filename> directory.
</para>
<para>
Below is a sample directory structure showing views and other resources like message bundles co-located with their flow definition:
</para>
<mediaobject>
<imageobject role="fo">
<imagedata fileref="images/flow-view-packaging.png" format="PNG" align="center"/>
</imageobject>
<imageobject role="html">
<imagedata fileref="images/flow-view-packaging.png" format="PNG" align="center"/>
</imageobject>
<caption>
<para>Flow Packaging</para>
</caption>
</mediaobject>
</sect1>
<sect1 id="view-explicit">
<title>Specifying view identifiers</title>
<para>
Use the <code>view</code> attribute to specify the id of the view to render explicitly.
</para>
<sect2 id="view-explicit-flowrelative">
<title>Flow relative view ids</title>
<para>
The view id may be a relative path to view resource in the flow's working directory:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" view="bookingDetails.xhtml">]]>
</programlisting>
</sect2>
<sect2 id="view-explicit-absolute">
<title>Absolute view ids</title>
<para>
The view id may be a absolute path to a view resource in the webapp root directory:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" view="/WEB-INF/hotels/booking/bookingDetails.xhtml">]]>
</programlisting>
</sect2>
<sect2 id="view-explicit-logical">
<title>Logical view ids</title>
<para>
With some view frameworks, such as Spring MVC's view framework, the view id may also be a logical identifier resolved by the framework:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" view="bookingDetails">]]>
</programlisting>
<para>
See the Spring MVC integration section for more information on how to integrate with the MVC <code>ViewResolver</code> infrastructure.
</para>
</sect2>
</sect1>
<sect1 id="view-scope">
<title>View scope</title>
<para>
A view-state allocates a new <code>viewScope</code> when it enters.
This scope may be referenced within the view-state to assign variables that should live for the duration of the state.
This scope is useful for manipulating objects over a series of requests from the same view, often Ajax requests.
A view-state destroys its viewScope when it exits.
</para>
<sect2 id="view-scope-var">
<title>Allocating view variables</title>
<para>
Use the <code>var</code> tag to declare a view variable.
Like a flow variable, any <code>@Autowired</code> references are automatically restored when the view state resumes.
</para>
<programlisting language="xml"><![CDATA[
<var name="searchCriteria" class="com.mycompany.myapp.hotels.SearchCriteria" />]]>
</programlisting>
</sect2>
<sect2 id="view-scope-actions">
<title>Assigning a viewScope variable</title>
<para>
Use the <code>on-render</code> tag to assign a variable from an action result before the view renders:
</para>
<programlisting language="xml"><![CDATA[
<on-render>
<evaluate expression="bookingService.findHotels(searchCriteria)" result="viewScope.hotels" />
</on-render>]]>
</programlisting>
</sect2>
<sect2 id="view-scope-ajax">
<title>Manipulating objects in view scope</title>
<para>
Objects in view scope are often manipulated over a series of requests from the same view.
The following example pages through a search results list.
The list is updated in view scope before each render.
Asynchronous event handlers modify the current data page, then request re-rendering of the search results fragment.
</para>
<programlisting language="xml"><![CDATA[
<view-state id="searchResults">
<on-render>
<evaluate expression="bookingService.findHotels(searchCriteria)"
result="viewScope.hotels" />
</on-render>
<transition on="next">
<evaluate expression="searchCriteria.nextPage()" />
<render fragments="searchResultsFragment" />
</transition>
<transition on="previous">
<evaluate expression="searchCriteria.previousPage()" />
<render fragments="searchResultsFragment" />
</transition>
</view-state>]]>
</programlisting>
</sect2>
</sect1>
<sect1 id="view-on-render">
<title>Executing render actions</title>
<para>
Use the <code>on-render</code> element to execute one or more actions before view rendering.
Render actions are executed on the initial render as well as any subsequent refreshes, including any partial re-renderings of the view.
</para>
<programlisting language="xml"><![CDATA[
<on-render>
<evaluate expression="bookingService.findHotels(searchCriteria)" result="viewScope.hotels" />
</on-render>]]>
</programlisting>
</sect1>
<sect1 id="view-model">
<title>Binding to a model</title>
<para>
Use the <code>model</code> attribute to declare a model object the view binds to.
This attribute is typically used in conjunction with views that render data controls, such as forms.
It enables form data binding and validation behaviors to be driven from metadata on your model object.
</para>
<para>
The following example declares an <code>enterBookingDetails</code> state manipulates the <code>booking</code> model:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" model="booking">]]>
</programlisting>
<para>
The model may be an object in any accessible scope, such as <code>flowScope</code> or <code>viewScope</code>.
Specifying a <code>model</code> triggers the following behavior when a view event occurs:
</para>
<orderedlist>
<listitem><para>View-to-model binding. On view postback, user input values are bound to model object properties for you.</para></listitem>
<listitem><para>Model validation. After binding, if the model object requires validation that validation logic will be invoked.</para></listitem>
</orderedlist>
<para>
For a flow event to be generated that can drive a view state transition, model binding must complete successfully.
If model binding fails, the view is re-rendered to allow the user to revise their edits.
</para>
</sect1>
<sect1 id="view-type-conversion">
<title>Performing type conversion</title>
<para>
When request parameters are used to populate the model (commonly referred to as data binding), type conversion is required to parse String-based request parameter values before setting target model properties.
Default type conversion is available for many common Java types such as numbers, primitives, enums, and Dates.
Users also have the ability to register their own type conversion logic for user-defined types, and to override the default Converters.
</para>
<sect2 id="converter-options">
<title>Type Conversion Options</title>
<para>
Starting with version 2.1 Spring Web Flow uses the <ulink url="http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/validation.html#core-convert">type conversion</ulink> and <ulink url="http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/validation.html#format">formatting</ulink> system introduced in Spring 3 for nearly all type conversion needs.
Previously Web Flow applications used a type conversion mechanism that was different from the one in Spring MVC, which relied on the <code>java.beans.PropertyEditor</code> abstraction.
Spring 3 offers a modern type conversion alternative to PropertyEditors that was actually influenced by Web Flow's own type conversion system.
Hence Web Flow users should find it natural to work with the new Spring 3 type conversion.
Another obvious and very important benefit of this change is that a single type conversion mechanism can now be used across Spring MVC And Spring Web Flow.
</para>
</sect2>
<sect2 id="converter-upgrade-to-spring-3">
<title>Upgrading to Spring 3 Type Conversion And Formatting</title>
<para>
What does this practically mean for existing applications?
Existing applications are likely registering their own converters of type <code>org.springframework.binding.convert.converters.Converter</code> through a sub-class of <code>DefaultConversionService</code> available in Spring Binding.
Those converters can continue to be registered as before.
They will be adapted as Spring 3 <code>GenericConverter</code> types and registered with a Spring 3 <code>org.springframework.core.convert.ConversionService</code> instance.
In other words existing converters will be invoked through Spring's type conversion service.
</para>
<para>
The only exception to this rule are named converters, which can be referenced from a <code>binding</code> element in a <code>view-state</code>:
<programlisting language="java"><![CDATA[
public class ApplicationConversionService extends DefaultConversionService {
public ApplicationConversionService() {
addDefaultConverters();
addDefaultAliases();
addConverter("customConverter", new CustomConverter());
}
}]]>
</programlisting>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" model="booking">
<binder>
<binding property="checkinDate" required="true" converter="customConverter" />
</binder>
</view-state>]]>
</programlisting>
Named converters are not supported and cannot be used with the type conversion service available in Spring 3.
Therefore such converters will not be adapted and will continue to work as before, i.e. will not involve the Spring 3 type conversion.
However, this mechanism is deprecated and applications are encouraged to favor Spring 3 type conversion and formatting features.
</para>
<para>
Also note that the existing Spring Binding <code>DefaultConversionService</code> no longer registers any default converters.
Instead Web Flow now relies on the default type converters and formatters in Spring 3.
</para>
<para>
In summary the Spring 3 type conversion and formatting is now used almost exclusively in Web Flow.
Although existing applications will work without any changes, we encourage moving towards unifying the type conversion needs of Spring MVC and Spring Web Flow parts of applications.
</para>
</sect2>
<sect2 id="converter-configuration">
<title>Configuring Type Conversion and Formatting</title>
<para>
In Spring MVC an instance of a <code>FormattingConversionService</code> is created automatically through the custom MVC namespace:
<programlisting language="xml"><![CDATA[
<?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:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<mvc:annotation-driven/>
]]>
</programlisting>
Internally that is done with the help of <code>FormattingConversionServiceFactoryBean</code>, which registers a default set of converters and formatters.
You can customize the conversion service instance used in Spring MVC through the <code>conversion-service</code> attribute:
<programlisting language="xml"><![CDATA[
<mvc:annotation-driven conversion-service="applicationConversionService" />]]>
</programlisting>
</para>
<para>
In Web Flow an instance of a Spring Binding <code>DefaultConversionService</code> is created automatically, which does not register any converters.
Instead it delegates to a <code>FormattingConversionService</code> instance for all type conversion needs.
By default this is not the same <code>FormattingConversionService</code> instance as the one used in Spring 3.
However that won't make a practical difference until you start registering your own formatters.
</para>
<para>
The <code>DefaultConversionService</code> used in Web Flow can be customized through the flow-builder-services element:
<programlisting language="xml"><![CDATA[
<webflow:flow-builder-services id="flowBuilderServices" conversion-service="defaultConversionService" />]]>
</programlisting>
</para>
<para>
Connecting the dots in order to register your own formatters for use in both Spring MVC and in Spring Web Flow you can do the following.
Create a class to register your custom formatters:
<programlisting language="java"><![CDATA[
public class ApplicationConversionServiceFactoryBean extends FormattingConversionServiceFactoryBean {
@Override
protected void installFormatters(FormatterRegistry registry) {
// ...
}
}
]]>
</programlisting>
Configure it for use in Spring MVC:
<programlisting language="xml"><![CDATA[
<?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:mvc="http://www.springframework.org/schema/mvc"
xsi:schemaLocation="
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<mvc:annotation-driven conversion-service="applicationConversionService" />
<!--
Alternatively if you prefer annotations for DI:
1. Add @Component to the factory bean.
2. Add a component-scan element (from the context custom namespace) here.
3. Remove XML bean declaration below.
-->
<bean id="applicationConversionService" class="somepackage.ApplicationConversionServiceFactoryBean">
]]>
</programlisting>
Connection the Web Flow <code>DefaultConversionService</code> to the same "applicationConversionService" bean used in Spring MVC:
<programlisting language="xml"><![CDATA[
<webflow:flow-registry id="flowRegistry" flow-builder-services="flowBuilderServices" ... />
<webflow:flow-builder-services id="flowBuilderServices" conversion-service="defaultConversionService" ... />
<bean id="defaultConversionService" class="org.springframework.binding.convert.service.DefaultConversionService">
<constructor-arg ref="applicationConversionSevice"/>
</bean>]]>
</programlisting>
Of course it is also possible to mix and match.
Register new Spring 3 <code>Formatter</code> types through the "applicationConversionService".
Register existing Spring Binding <code>Converter</code> types through the "defaultConversionService".
</para>
</sect2>
<sect2 id="converter-working-with">
<title>Working With Spring 3 Type Conversion And Formatting</title>
<para>
An important concept to understand is the difference between type converters and formatters.
</para>
<para>
Type converters in Spring 3, provided in <code>org.springframework.core</code>, are for general-purpose type conversion between any two object types.
In addition to the most simple <code>Converter</code> type, two other interfaces are <code>ConverterFactory</code> and <code>GenericConverter</code>.
</para>
<para>
Formatters in Spring 3, provided in <code>org.springframework.context</code>, have the more specialized purpose of representing Objects as Strings.
The <code>Formatter</code> interface extends the <code>Printer</code> and <code>Parser</code> interfaces for converting an Object to a String and turning a String into an Object.
</para>
<para>
Web developers will find the <code>Formatter</code> interface most relevant because it fits the needs of web applications for type conversion.
<note>
<para>
An important point to be made is that Object-to-Object conversion is a generalization of the more specific Object-to-String conversion.
In fact in the end <code>Formatters</code> are reigstered as <code>GenericConverter</code> types with Spring's <code>GenericConversionService</code> making them equal to any other converter.
</para>
</note>
</para>
</sect2>
<sect2 id="converter-formatting-annotations">
<title>Formatting Annotations</title>
<para>
One of the best features of the new type conversion is the ability to use annotations for a better control over formatting in a concise manner.
Annotations can be placed on model attributes and on arguments of @Controller methods that are mapped to requests.
Out of the box Spring provides two annotations <code>NumberFormat</code> and <code>DateTimeFormat</code> but you can create your own and have them registered along with the associated formatting logic.
You can see examples of the <code>DateTimeFormat</code> annotation in the <ulink url="https://src.springframework.org/svn/spring-samples/travel">Spring Travel</ulink> and in the <ulink url="https://src.springframework.org/svn/spring-samples/petcare">Petcare</ulink> along with other samples in the <ulink url="https://src.springframework.org/svn/spring-samples">Spring Samples</ulink> repository.
</para>
</sect2>
<sect2 id="converter-dates">
<title>Working With Dates</title>
<para>
The <code>DateTimeFormat</code> annotation implies use of <ulink url="http://joda-time.sourceforge.net/">Joda Time</ulink>.
If that is present on the classpath the use of this annotation is enabled automatically.
By default neither Spring MVC nor Web Flow register any other date formatters or converters.
Therefore it is important for applications to register a custom formatter to specify the default way for printing and parsing dates.
The <code>DateTimeFormat</code> annotation on the other hand provides more fine-grained control where it is necessary to deviate from the default.
</para>
<para>
For more information on working with Spring 3 type conversion and formatting please refer to the relevant sections of the <ulink url="http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/index.html">Spring documentation</ulink>.
</para>
</sect2>
</sect1>
<sect1 id="view-bind">
<title>Suppressing binding</title>
<para>
Use the <code>bind</code> attribute to suppress model binding and validation for particular view events.
The following example suppresses binding when the <code>cancel</code> event occurs:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" model="booking">
<transition on="proceed" to="reviewBooking">
<transition on="cancel" to="bookingCancelled" bind="false" />
</view-state>]]>
</programlisting>
</sect1>
<sect1 id="view-binder">
<title>Specifying bindings explicitly</title>
<para>
Use the <code>binder</code> element to configure the exact set of model bindings usable by the view.
This is particularly useful in a Spring MVC environment for restricting the set of "allowed fields" per view.
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" model="booking">
<binder>
<binding property="creditCard" />
<binding property="creditCardName" />
<binding property="creditCardExpiryMonth" />
<binding property="creditCardExpiryYear" />
</binder>
<transition on="proceed" to="reviewBooking" />
<transition on="cancel" to="cancel" bind="false" />
</view-state>
]]>
</programlisting>
<para>
If the binder element is not specified, all public properties of the model are eligible for binding by the view.
With the binder element specified, only the explicitly configured bindings are allowed.
</para>
<para>
Each binding may also apply a converter to format the model property value for display in a custom manner.
If no converter is specified, the default converter for the model property's type will be used.
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" model="booking">
<binder>
<binding property="checkinDate" converter="shortDate" />
<binding property="checkoutDate" converter="shortDate" />
<binding property="creditCard" />
<binding property="creditCardName" />
<binding property="creditCardExpiryMonth" />
<binding property="creditCardExpiryYear" />
</binder>
<transition on="proceed" to="reviewBooking" />
<transition on="cancel" to="cancel" bind="false" />
</view-state>
]]>
</programlisting>
<para>
In the example above, the <code>shortDate</code> converter is bound to the
<code>checkinDate</code> and <code>checkoutDate</code> properties.
Custom converters may be registered with the application's ConversionService.
</para>
<para>
Each binding may also apply a required check that will generate a validation error
if the user provided value is null on form postback:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" model="booking">
<binder>
<binding property="checkinDate" converter="shortDate" required="true" />
<binding property="checkoutDate" converter="shortDate" required="true" />
<binding property="creditCard" required="true" />
<binding property="creditCardName" required="true" />
<binding property="creditCardExpiryMonth" required="true" />
<binding property="creditCardExpiryYear" required="true" />
</binder>
<transition on="proceed" to="reviewBooking">
<transition on="cancel" to="bookingCancelled" bind="false" />
</view-state>]]>
</programlisting>
<para>
In the example above, all of the bindings are required.
If one or more blank input values are bound, validation errors will be generated and the view will re-render with those errors.
</para>
</sect1>
<sect1 id="view-validate">
<title>Validating a model</title>
<para>
Model validation is driven by constraints specified against a model object.
Web Flow supports enforcing such constraints programatically as well as
declaratively with JSR-303 Bean Validation annotations.
</para>
<sect2 id="view-validation-jsr303">
<title>JSR-303 Bean Validation</title>
<para>
Web Flow provides built-in support for the JSR-303 Bean Validation API
building on equivalent support available in Spring MVC.
To enable JSR-303 validation configure the flow-builder-services with
Spring MVC's <code>LocalValidatorFactoryBean</code>:
</para>
<programlisting language="xml">
&lt;webflow:flow-registry flow-builder-services="flowBuilderServices" /&gt;
&lt;webflow:flow-builder-services id="flowBuilderServices" validator="validator" /&gt;
&lt;bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean" /&gt;
</programlisting>
<para>
With the above in place, the configured validator will be applied to
all model attributes after data binding.
</para>
<para>
Note that JSR-303 bean validation and validation by convention
(explained in the next section) are not mutually exclusive.
In other words Web Flow will apply all available validation
mechanisms.
</para>
</sect2>
<sect2 id="view-validation-programmatic">
<title>Programmatic validation</title>
<para>
There are two ways to perform model validation programatically.
The first is to implement validation logic in your model object.
The second is to implement an external <code>Validator</code>.
Both ways provide you with a <code>ValidationContext</code> to record error messages and access information about the current user.
</para>
<sect3 id="view-validation-programmatic-validate-method">
<title>Implementing a model validate method</title>
<para>
Defining validation logic in your model object is the simplest way to validate its state.
Once such logic is structured according to Web Flow conventions, Web Flow will automatically invoke that logic during the view-state postback lifecycle.
Web Flow conventions have you structure model validation logic by view-state, allowing you to easily validate the subset of model properties that are editable on that view.
To do this, simply create a public method with the name <code>validate${state}</code>, where <code>${state}</code> is the id of your view-state where you want validation to run.
For example:
<programlisting language="java"><![CDATA[
public class Booking {
private Date checkinDate;
private Date checkoutDate;
...
public void validateEnterBookingDetails(ValidationContext context) {
MessageContext messages = context.getMessageContext();
if (checkinDate.before(today())) {
messages.addMessage(new MessageBuilder().error().source("checkinDate").
defaultText("Check in date must be a future date").build());
} else if (!checkinDate.before(checkoutDate)) {
messages.addMessage(new MessageBuilder().error().source("checkoutDate").
defaultText("Check out date must be later than check in date").build());
}
}
}
]]>
</programlisting>
</para>
<para>
In the example above, when a transition is triggered in a <code>enterBookingDetails</code> view-state that is editing a <code>Booking</code> model,
Web Flow will invoke the <code>validateEnterBookingDetails(ValidationContext)</code> method automatically unless validation has been suppressed for that transition.
An example of such a view-state is shown below:
<programlisting language="xml"><![CDATA[
<view-state id="enterBookingDetails" model="booking">
<transition on="proceed" to="reviewBooking">
</view-state>]]>
</programlisting>
</para>
<para>
Any number of validation methods are defined. Generally, a flow edits a model over a series of views. In that case, a validate method would be defined
for each view-state where validation needs to run.
</para>
</sect3>
<sect3 id="view-validation-programmatic-validator">
<title>Implementing a Validator</title>
<para>
The second way is to define a separate object, called a <emphasis>Validator</emphasis>, which validates your model object.
To do this, first create a class whose name has the pattern ${model}Validator, where <code>${model}</code> is the capitialized form of the model expression, such as <code>booking</code>.
Then define a public method with the name <code>validate${state}</code>, where <code>${state}</code> is the id of your view-state, such as <code>enterBookingDetails</code>.
The class should then be deployed as a Spring bean. Any number of validation methods can be defined.
For example:
</para>
<programlisting language="java"><![CDATA[
@Component
public class BookingValidator {
public void validateEnterBookingDetails(Booking booking, ValidationContext context) {
MessageContext messages = context.getMessageContext();
if (booking.getCheckinDate().before(today())) {
messages.addMessage(new MessageBuilder().error().source("checkinDate").
defaultText("Check in date must be a future date").build());
} else if (!booking.getCheckinDate().before(booking.getCheckoutDate())) {
messages.addMessage(new MessageBuilder().error().source("checkoutDate").
defaultText("Check out date must be later than check in date").build());
}
}
}]]>
</programlisting>
<para>
In the example above, when a transition is triggered in a <code>enterBookingDetails</code> view-state that is editing a <code>Booking</code> model,
Web Flow will invoke the <code>validateEnterBookingDetails(Booking, ValidationContext)</code> method automatically unless validation has been suppressed for that transition.
</para>
<para>
A Validator can also accept a Spring MVC <code>Errors</code> object, which is required for invoking existing Spring Validators.
</para>
<para>
Validators must be registered as Spring beans employing the naming convention <code>${model}Validator</code> to be detected and invoked automatically.
In the example above, Spring 2.5 classpath-scanning would detect the <code>@Component</code> and automatically register it as a bean with the name <code>bookingValidator</code>.
Then, anytime the <code>booking</code> model needs to be validated, this <code>bookingValidator</code> instance would be invoked for you.
</para>
</sect3>
<sect3 id="default-validate-method">
<title>Default validate method</title>
<para>
A <emphasis>Validator</emphasis> class can also define a method called <code>validate</code> not associated (by convention) with any specific view-state.
</para>
<programlisting language="java"><![CDATA[
@Component
public class BookingValidator {
public void validate(Booking booking, ValidationContext context) {
//...
}
}]]>
</programlisting>
<para>
In the above code sample the method <code>validate</code> will be called every time a Model of type <code>Booking</code> is validated (unless validation has been suppressed for that transition).
If needed the default method can also be called in addition to an existing state-specific method. Consider the following example:
</para>
<programlisting language="java"><![CDATA[
@Component
public class BookingValidator {
public void validate(Booking booking, ValidationContext context) {
//...
}
public void validateEnterBookingDetails(Booking booking, ValidationContext context) {
//...
}
}]]>
</programlisting>
<para>
In above code sample the method <code>validateEnterBookingDetails</code> will be called first.
The default <code>validate</code> method will be called next.
</para>
</sect3>
</sect2>
<sect2 id="view-validation-context">
<title>ValidationContext</title>
<para>
A ValidationContext allows you to obtain a <code>MessageContext</code> to record messages during validation.
It also exposes information about the current user, such as the signaled <code>userEvent</code> and the current user's <code>Principal</code> identity.
This information can be used to customize validation logic based on what button or link was activated in the UI, or who is authenticated.
See the API Javadocs for <code>ValidationContext</code> for more information.
</para>
</sect2>
</sect1>
<sect1 id="view-validation-suppression">
<title>Suppressing validation</title>
<para>
Use the <code>validate</code> attribute to suppress model validation for particular view events:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="chooseAmenities" model="booking">
<transition on="proceed" to="reviewBooking">
<transition on="back" to="enterBookingDetails" validate="false" />
</view-state>]]>
</programlisting>
<para>
In this example, data binding will still occur on <code>back</code> but validation will be suppressed.
</para>
</sect1>
<sect1 id="view-transitions">
<title>Executing view transitions</title>
<para>
Define one or more <code>transition</code> elements to handle user events that may occur on the view.
A transition may take the user to another view, or it may simply execute an action and re-render the current view.
A transition may also request the rendering of parts of a view called "fragments" when handling an Ajax event.
Finally, "global" transitions that are shared across all views may also be defined.
</para>
<para>
Implementing view transitions is illustrated in the following sections.
</para>
<sect2 id="transition-actions">
<title>Transition actions</title>
<para>
A view-state transition can execute one or more actions before executing.
These actions may return an error result to prevent the transition from exiting the current view-state.
If an error result occurs, the view will re-render and should display an appropriate message to the user.
</para>
<para>
If the transition action invokes a plain Java method, the invoked method may return false to prevent the transition from executing.
This technique can be used to handle exceptions thrown by service-layer methods.
The example below invokes an action that calls a service and handles an exceptional situation:
</para>
<programlisting language="xml"><![CDATA[
<transition on="submit" to="bookingConfirmed">
<evaluate expression="bookingAction.makeBooking(booking, messageContext)" />
</transition>]]>
</programlisting>
<programlisting language="java"><![CDATA[
public class BookingAction {
public boolean makeBooking(Booking booking, MessageContext context) {
try {
bookingService.make(booking);
return true;
} catch (RoomNotAvailableException e) {
context.addMessage(new MessageBuilder().error().
.defaultText("No room is available at this hotel").build());
return false;
}
}
}]]>
</programlisting>
<note>
<para>
When there is more than one action defined on a transition, if one returns an error result the remaining actions in the set will <emphasis>not</emphasis> be executed.
If you need to ensure one transition action's result cannot impact the execution of another, define a single transition action that invokes a method that encapsulates all the action logic.
</para>
</note>
</sect2>
<sect2 id="event-handlers-global">
<title>Global transitions</title>
<para>
Use the flow's <code>global-transitions</code> element to create transitions that apply across all views.
Global-transitions are often used to handle global menu links that are part of the layout.
</para>
<programlisting language="xml"><![CDATA[
<global-transitions>
<transition on="login" to="login" />
<transition on="logout" to="logout" />
</global-transitions>]]>
</programlisting>
</sect2>
<sect2 id="simple-event-handlers">
<title>Event handlers</title>
<para>
From a view-state, transitions without targets can also be defined. Such transitions are called "event handlers":
</para>
<programlisting language="xml"><![CDATA[
<transition on="event">
<!-- Handle event -->
</transition>]]>
</programlisting>
<para>
These event handlers do not change the state of the flow.
They simply execute their actions and re-render the current view or one or more fragments of the current view.
</para>
</sect2>
<sect2 id="event-handlers-render">
<title>Rendering fragments</title>
<para>
Use the <code>render</code> element within a transition to request partial re-rendering of the current view after handling the event:
</para>
<programlisting language="xml"><![CDATA[
<transition on="next">
<evaluate expression="searchCriteria.nextPage()" />
<render fragments="searchResultsFragment" />
</transition>]]>
</programlisting>
<para>
The fragments attribute should reference the id(s) of the view element(s) you wish to re-render.
Specify multiple elements to re-render by separating them with a comma delimiter.
</para>
<para>
Such partial rendering is often used with events signaled by Ajax to update a specific zone of the view.
</para>
</sect2>
</sect1>
<sect1 id="view-messages">
<title>Working with messages</title>
<para>
Spring Web Flow's <code>MessageContext</code> is an API for recording messages during the course of flow executions.
Plain text messages can be added to the context, as well as internationalized messages resolved by a Spring <code>MessageSource</code>.
Messages are renderable by views and automatically survive flow execution redirects.
Three distinct message severities are provided: <code>info</code>, <code>warning</code>, and <code>error</code>.
In addition, a convenient <code>MessageBuilder</code> exists for fluently constructing messages.
</para>
<sect2 id="plain-text-message">
<title>Adding plain text messages</title>
<programlisting language="java"><![CDATA[
MessageContext context = ...
MessageBuilder builder = new MessageBuilder();
context.addMessage(builder.error().source("checkinDate")
.defaultText("Check in date must be a future date").build());
context.addMessage(builder.warn().source("smoking")
.defaultText("Smoking is bad for your health").build());
context.addMessage(builder.info()
.defaultText("We have processed your reservation - thank you and enjoy your stay").build());]]>
</programlisting>
</sect2>
<sect2 id="plain-text-message-intl">
<title>Adding internationalized messages</title>
<programlisting language="java"><![CDATA[
MessageContext context = ...
MessageBuilder builder = new MessageBuilder();
context.addMessage(builder.error().source("checkinDate").code("checkinDate.notFuture").build());
context.addMessage(builder.warn().source("smoking").code("notHealthy")
.resolvableArg("smoking").build());
context.addMessage(builder.info().code("reservationConfirmation").build());]]>
</programlisting>
</sect2>
<sect2 id="message-bundles">
<title>Using message bundles</title>
<para>
Internationalized messages are defined in message bundles accessed by a Spring <code>MessageSource</code>.
To create a flow-specific message bundle, simply define <code>messages.properties</code> file(s) in your flow's directory.
Create a default <code>messages.properties</code> file and a .properties file for each additional <code>Locale</code> you need to support.
</para>
<programlisting><![CDATA[
#messages.properties
checkinDate=Check in date must be a future date
notHealthy={0} is bad for your health
reservationConfirmation=We have processed your reservation - thank you and enjoy your stay]]>
</programlisting>
<para>
From within a view or a flow, you may also access message resources using the <code>resourceBundle</code> EL variable:
</para>
<programlisting><![CDATA[
<h:outputText value="#{resourceBundle.reservationConfirmation}" />]]>
</programlisting>
</sect2>
<sect2 id="message-generation">
<title>Understanding system generated messages</title>
<para>
There are several places where Web Flow itself will generate messages to display to the user.
One important place this occurs is during view-to-model data binding.
When a binding error occurs, such as a type conversion error, Web Flow will map that error to a message retrieved from your resource bundle automatically.
To lookup the message to display, Web Flow tries resource keys that contain the binding error code and target property name.
</para>
<para>
As an example, consider a binding to a <code>checkinDate</code> property of a <code>Booking</code> object.
Suppose the user typed in a alphabetic string.
In this case, a type conversion error will be raised.
Web Flow will map the 'typeMismatch' error code to a message by first querying your resource bundle for a message with the following key:
</para>
<programlisting>
booking.checkinDate.typeMismatch
</programlisting>
<para>
The first part of the key is the model class's short name.
The second part of the key is the property name. The third part is the error code.
This allows for the lookup of a unique message to display to the user when a binding fails on a model property.
Such a message might say:
</para>
<programlisting>
booking.checkinDate.typeMismatch=The check in date must be in the format yyyy-mm-dd.
</programlisting>
<para>
If no such resource key can be found of that form, a more generic key will be tried.
This key is simply the error code. The field name of the property is provided as a message argument.
</para>
<programlisting>
typeMismatch=The {0} field is of the wrong type.
</programlisting>
</sect2>
</sect1>
<sect1 id="view-popup">
<title>Displaying popups</title>
<para>
Use the <code>popup</code> attribute to render a view in a modal popup dialog:
</para>
<programlisting language="xml"><![CDATA[
<view-state id="changeSearchCriteria" view="enterSearchCriteria.xhtml" popup="true">]]>
</programlisting>
<para>
When using Web Flow with the Spring Javascript, no client side code is necessary for the popup to display.
Web Flow will send a response to the client requesting a redirect to the view from a popup, and the client will honor the request.
</para>
</sect1>
<sect1 id="view-backtracking">
<title>View backtracking</title>
<para>
By default, when you exit a view state and transition to a new view state, you can go back to the previous state using the browser back button.
These view state history policies are configurable on a per-transition basis by using the <code>history</code> attribute.
</para>
<sect2 id="history-discard">
<title>Discarding history</title>
<para>
Set the history attribute to <code>discard</code> to prevent backtracking to a view:
</para>
<programlisting language="xml"><![CDATA[
<transition on="cancel" to="bookingCancelled" history="discard">]]>
</programlisting>
</sect2>
<sect2 id="history-invalidate">
<title>Invalidating history</title>
<para>
Set the history attribute to <code>invalidate</code> to prevent backtracking to a view as well all previously displayed views:
</para>
<programlisting language="xml"><![CDATA[
<transition on="confirm" to="bookingConfirmed" history="invalidate">]]>
</programlisting>
</sect2>
</sect1>
</chapter>

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<?xml version="1.0" encoding="UTF-8"?>
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
xml:id="whatsnew">
<title>What's New</title>
<sect1 id="whatsnew-swf-230">
<title>Spring Web Flow 2.3</title>
<sect2 id="whatsnew-swf-embedded-flow">
<title>Embedding A Flow On A Page</title>
<para>
By default Web Flow does a client-side redirect upon entering every view state.
That makes it impossible to embed a flow on a page or within a modal dialog and execute more than one view state without causing a full-page refresh.
Web Flow now supports launching a flow in "embedded" mode.
In this mode a flow can transition to other view states without a client-side redirect during Ajax requests.
See <xref linkend="spring-mvc-embedded-flow"/> and <xref linkend="spring-faces-embedded-mode"/>.
</para>
</sect2>
<sect2 id="whatsnew-jsr303">
<title>Support For JSR-303 Bean Validation</title>
<para>
Support for the JSR-303 Bean Validation API is now available building on equivalent support available in Spring MVC.
See <xref linkend="view-validate"/> for more details.
</para>
</sect2>
<sect2 id="whatsnew-pc-propagation">
<title>Flow-Managed Persistence Context Propagation</title>
<para>
Starting with Web Flow 2.3 a flow managed <code>PersistenceContext</code> is automatically extended (propagated) to sub-flows assuming the subflow also has the feature enabled as well.
See <xref linkend="flow-managed-persistence-propagation"/>.
</para>
</sect2>
<sect2 id="whatsnew-portlet-resource-requests">
<title>Portlet 2.0 Resource Requests</title>
<para>
Support for Portlet 2.0 resource requests has now been added enabling Ajax requests with partial rendering.
URLs for such requests can be prepared with the <code>&lt;portlet:resourceURL&gt;</code> tag in JSP pages.
Server-side processing is similar to a combined an action and a render requests but combined in a single request.
Unlike a render request, the response from a resource request includes content from the target portlet only.
</para>
</sect2>
<sect2 id="whatsnew-conversation-manager">
<title>Custom ConversationManager</title>
<para>
The <code>&lt;flow-execution-repository&gt;</code> element now provides a conversation-manager attribute accepting a reference to a ConversationManager instance.
</para>
</sect2>
<sect2 id="whatsnew-redirect-in-same-state">
<title>Redirect In Same State</title>
<para>
By default Web Flow does a client-side redirect when remaining in the same view state as long as the current request is not an Ajax request.
This is useful after form validation failure.
Hitting Refresh or Back won't result in browser warnings.
Hence this behavior is usually desirable.
However a new flow execution attribute makes it possible to disable it and that may also be necessary in some cases specific to JSF 2 applications.
See <xref linkend="spring-faces-redirect-in-same-state"/>.
</para>
</sect2>
<sect2 id="whatsnew-samples">
<title>Samples</title>
<para>
The process for building the samples included with the distribution has been simplified.
Maven can be used to build all samples in one step.
Eclipse settings include source code references to simplify debugging.
</para>
<para>
Additional samples can be accessed as follows:
<programlisting language="xml">mkdir spring-samples
cd spring-samples
svn co https://src.springframework.org/svn/spring-samples/webflow-primefaces-showcase
cd webflow-primefaces-showcase
mvn package
# import into Eclipse
</programlisting>
<programlisting language="xml">mkdir spring-samples
cd spring-samples
svn co https://src.springframework.org/svn/spring-samples/webflow-showcase
cd webflow-showcase
mvn package
# import into Eclipse
</programlisting>
</para>
</sect2>
</sect1>
<sect1 id="whatsnew-swf-220">
<title>Spring Web Flow 2.2</title>
<sect2 id="whatsnew-jsf2">
<title>JSF 2 Support</title>
<sect3>
<title>Comprehensive JSF 2 Support</title>
<para>
Building on 2.1, Spring Web Flow version 2.2 adds support for core JSF 2 features
The following features that were not supported in 2.1 are now available:
partial state saving, JSF 2 resource request, handling, and JSF 2 Ajax requests.
At this point support for JSF 2 is considered
comprehensive although not covering every JSF 2 feature --
excluded are mostly features that overlap with the core value Web Flow provides
such as those relating to navigation and state management.
</para>
<para>
See <xref linkend="spring-faces-webflow-config"/> for important configuration changes.
Note that partial state saving is only supported with Sun Mojarra 2.0.3 or later.
It is not yet supported with Apache MyFaces. This is due to the
fact MyFaces was not as easy to customize with regards to how component state is stored.
We will work with Apache MyFaces to provide this support. In the mean time you will need to use
the <code>javax.faces.PARTIAL_STATE_SAVING</code> context parameter in <code>web.xml</code>
to disable partial state saving with Apache MyFaces.
</para>
</sect3>
<sect3>
<title>Travel Sample With the PrimeFaces Components</title>
<para>
The main Spring Travel sample demonstrating Spring Web Flow and JSF support
is now built on JSF 2 and components from the PrimeFaces component library.
Please check out the booking-faces sample in the distribution.
</para>
<para>
Additional samples can be found at the Spring Web Flow - Prime Faces
<ulink url="https://src.springframework.org/svn/spring-samples/webflow-primefaces-showcase">
Showcase</ulink>, an SVN repository within the
<ulink url="https://src.springframework.org/svn/spring-samples">spring-samples</ulink>
repository. Use these commands to check out and build:
</para>
<programlisting><![CDATA[svn co https://src.springframework.org/svn/spring-samples/webflow-primefaces-showcase
cd webflow-primefaces-showcase
mvn package
]]></programlisting>
</sect3>
</sect2>
<sect2 id="whatsnew-sec">
<title>Spring Security Facelets Tag Library</title>
<para>
A new Spring Security tag library is available for use with with JSF 2.0 or with JSF 1.2 Facelets views.
It provides an &lt;authorize&gt; tag as well as several EL functions.
See <xref linkend="spring-faces-security-taglib"/> for more details.
</para>
</sect2>
<sect2 id="whatsnew-versions">
<title>Spring JavaScript Updates</title>
<sect3>
<title>Deprecated ResourcesServlet</title>
<para>
Starting with Spring 3.0.4, the Spring Framework includes
a replacement for the ResourcesServlet. Please see
the Spring Framework documentation for details on the custom mvc namespace,
specifically the new
<ulink url="http://static.springsource.org/spring/docs/3.0.x/spring-framework-reference/html/mvc.html#mvc-static-resources">"resources"</ulink>
element.
</para>
</sect3>
<sect3>
<title>Dojo 1.5 and dojox</title>
<para>
The bundled custom Dojo build is upgraded to version 1.5. It now includes dojox.
</para>
<para>
Note that applications are generally encouraged to prepare their own custom
Dojo build for optimized performance depending on what parts of Dojo are
commonly used together. For examples see the
<ulink url="https://src.springframework.org/svn/spring-webflow/branches/spring-webflow-2.2-maintenance/spring-js-resources/scripts/dojo">scripts</ulink>
used by Spring Web Flow to prepare its own custom Dojo build.
</para>
</sect3>
<sect3>
<title>Two Spring JS artifacts</title>
<para>
The <code>spring-js</code> artifact has been split in two -- the new artifact
(<code>spring-js-resources</code>) contains client side resource (.js, .css, etc.) while
the existing artifact (<code>spring-js</code>) contains server-side Java code only.
</para>
<para>
Applications preparing their own custom Dojo build have an option now to
avoid including <code>spring-js-resources</code> and put <code>Spring.js</code> and
<code>Spring-Dojo.js</code> directly under the root of their web application.
</para>
</sect3>
<sect3>
<title>Client resources moved into META-INF/web-resources</title>
<para>
Bundled client resources (.js, .css, etc.)
have been moved to <code>META-INF/web-resources</code> from their previous location
under <code>META-INF</code>. This change is transparent for applications but will result
in simpler and safer configuration when using the new resource handling
mechanism available in Spring 3.0.4.
</para>
</sect3>
</sect2>
<sect2 id="whatsnew-jsf-portlet">
<title>JFS Portlet Support</title>
<sect3>
<title>Portlet API 2.0 and JSF 1.2 support</title>
<para>
In previous versions of Spring Web Flow support for JSF Portlets relied on
a Portlet Bridge for JSF implementation and was considered experimental.
Spring Web Flow 2.2 adds support for JSF Portlets based on its own internal
Portlet integration targeting Portlet API 2.0 and JSF 1.2 environments.
See <xref linkend="portlet-jsf"/> for more details.
The Spring Web Flow Travel JSF Portlets sample has been successfully
tested on the Apache Pluto portal container.
</para>
</sect3>
</sect2>
</sect1>
</chapter>