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INT-1246, edited the XML based configuration and added a section for @Publisher being a meta-annotation

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Oleg Zhurakousky
2010-09-03 03:10:54 +00:00
parent 4677615b5a
commit 400832836d
1 changed files with 71 additions and 22 deletions
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93
src/docbkx/message-publishing.xml
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@@ -121,10 +121,46 @@ public String argumentAsPayload(@Payload String fname, @Header String lname) {
<programlisting language="xml">&lt;si:annotation-config default-publisher-channel="defaultChannel"/&gt;</programlisting>
</para>
<para>
Similar to other Spring annotations (e.g., @Controller), <classname>@Publisher</classname> is a meta-annotation, which means you can define your own annotations
that will be treated as <classname>@Publisher</classname>
<programlisting language="java"><![CDATA[@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Publisher(channel="auditChannel")
public @interface Audit {
}]]></programlisting>
Here we defined <classname>@Audit</classname> annotation which itself is a <classname>@Publisher</classname>. Also note that you can define <code>channel</code>
attribute on the meta-annotation thus encapsulating the behavior of where messages will be sent inside of this annotation.
Now you can annotate any method:
<programlisting language="java"><![CDATA[@Audit
public String test() {
    return "foo";
}]]></programlisting>
In the above example every invocation of <code>test()</code> method will result in Message with payload which is the return value of the method
invocation to be sent to <emphasis>auditChannel</emphasis>
You can also annotate the class which would mean that the properties of this annotation will be applied on every public method of this class
<programlisting language="java"><![CDATA[@Audit
static class BankingOperationsImpl implements BankingOperations {
  public String debit(String amount) {
     . . .
  }
  public String credit(String amount) {
     . . .
  }
}]]></programlisting>
</para>
</section>
<section id="aop-based-interceptor">
<title>XML-based approach via &lt;publisher&gt; element</title>
<title>XML-based approach via &lt;publishing-interceptor&gt; element</title>
<para>
The XML-based approach allows you to configure the same AOP-based Message Publishing functionality with
simple namespace-based configuration of a <classname>MessagePublishingInterceptor</classname>.
@@ -145,22 +181,22 @@ public String argumentAsPayload(@Payload String fname, @Header String lname) {
</itemizedlist>
</para>
<para>
<programlisting language="xml">
&lt;beans:bean id="testBean" class="org.foo.bar.TestBean" /&gt;
&lt;aop:config&gt;
&lt;aop:advisor advice-ref="interceptor" pointcut="bean(testBean)" /&gt;
&lt;/aop:config&gt;
&lt;publishing-interceptor id="interceptor" default-channel="defaultChannel"&gt;
&lt;method pattern="echo" payload="'Echoing: ' + #return" headers="foo='bar'" channel="echoChannel"/&gt;
&lt;method pattern="echoDef*" payload="#return"/&gt;
&lt;method pattern="foo*"/&gt;
&lt;/publishing-interceptor&gt;
</programlisting>
<programlisting language="xml"><![CDATA[<aop:config>
<aop:advisor advice-ref="interceptor" pointcut="bean(testBean)" />
</aop:config>
<publishing-interceptor id="interceptor" default-channel="defaultChannel">
<method pattern="echo" payload="'Echoing: ' + #return" channel="echoChannel">
<header name="foo" value="bar"/>
</method>
<method pattern="repl*" payload="'Echoing: ' + #return" channel="echoChannel">
<header name="foo" expression="'bar'.toUpperCase()"/>
</method>
<method pattern="echoDef*" payload="#return"/>
</publishing-interceptor>]]></programlisting>
</para>
<para>
As you can see the <code>&lt;publisher&gt;</code> element expects the same variables as the
<classname>PublisherAnnotationAdvisor</classname> and also utilizes the power of the Spring 3.0 Expression Language.
As you can see the <code>&lt;publishing-interceptor&gt;</code> configuration look rather similar to Annotation-based approach
and it also utilizes the power of the Spring 3.0 Expression Language.
</para>
<para>
In the above example the execution of the <code>echo</code> method of a <code>testBean</code> will
@@ -169,15 +205,31 @@ public String argumentAsPayload(@Payload String fname, @Header String lname) {
<listitem>
<para>The Message payload will be of type String and value of "Echoing: [value]" where <code>value</code> is the value
returned by an executed method.</para>
</listitem>
</listitem>
<listitem>
<para>The Message headers will contain the key "foo" with a value of "bar".</para>
<para>The Message will have header with the key "foo" value "bar".</para>
</listitem>
<listitem>
<para>The Message will be sent to <code>echoChannel</code>.</para>
</listitem>
</itemizedlist>
</para>
<para>
The second method is very siumilar to the first. Here every method that begings with 'repl' will rander a Message with teh following structure:
<itemizedlist>
<listitem>
<para>The Message payload will be the same as in the above sample</para>
</listitem>
<listitem>
<para>The Message will have header with the key "foo" and value that is the result of the SpEL expression <code>'bar'.toUpperCase()</code> .</para>
</listitem>
<listitem>
<para>The Message will be sent to <code>echoChannel</code>.</para>
</listitem>
</itemizedlist>
</para>
<para>
The second method, mapping the execution of any method that begins with <code>echoDef</code> of <code>testBean</code>, will produce a
Message with the following structure.
@@ -191,14 +243,11 @@ public String argumentAsPayload(@Payload String fname, @Header String lname) {
</listitem>
</itemizedlist>
</para>
<para>
The third mapping is almost identical to the previous one (with the exception of method pattern),
since the return value will be mapped to the Message payload by default if nothing else is specified.
</para>
<para>
For simple mapping rules you can rely on the <emphasis>publisher</emphasis> defaults. For example:
<programlisting language="xml">
&lt;publisher id="anotherInterceptor"/&gt;
&lt;publishing-interceptor id="anotherInterceptor"/&gt;
</programlisting>
This will map the return value of every method that matches the pointcut expression to a payload and will be sent to a <emphasis>default-channel</emphasis>.
If the <emphasis>defaultChannel</emphasis>is not specified (as above) the messages will be sent to the global <emphasis>nullChannel</emphasis>.