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Added Channel Adapter and Service Activator chapters

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Mark Fisher
2008-11-03 01:51:38 +00:00
parent e375776811
commit cb6c2c8c50
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spring-integration-reference/src/service-activator.xml Normal file
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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<chapter id="service-activator">
<title>Service Activator</title>
<section id="service-activator-introduction">
<title>Introduction</title>
<para>
The Service Activator is the endpoint type for connecting any Spring-managed Object to an input channel so that
it may play the role of a service. If the service produces output, it may also be connected to an output channel.
Alternatively, an output producing service may be located at the end of a processing pipeline or message flow in
which case, the inbound Message's "replyChannel" header can be used. This is the default behavior if no output
channel is defined, and as with most of the configuration options you'll see here, the same behavior actually
applies for most of the other components we have seen.
</para>
</section>
<section id="service-activator-namespace">
<title>The &lt;service-activator/&gt; Element</title>
<para>
To create a Service Activator, use the 'service-activator' element with the 'input-channel' and 'ref' attributes:
<programlisting language="xml">&lt;service-activator input-channel="exampleChannel" ref="exampleHandler"/&gt;</programlisting>
</para>
<para>
The configuration above assumes that "exampleHandler" either contains a single method annotated with the
@ServiceActivator annotation or that it contains only one public method at all. To delegate to an explicitly
defined method of any object, simply add the "method" attribute.
<programlisting language="xml">&lt;service-activator input-channel="exampleChannel" ref="somePojo" method="someMethod"/&gt;</programlisting>
</para>
<para>
In either case, when the service method returns a non-null value, the endpoint will attempt to send the reply
message to an appropriate reply channel. To determine the reply channel, it will first check if an
"output-channel" was provided in the endpoint configuration:
<programlisting language="xml">&lt;service-activator input-channel="exampleChannel" output-channel="replyChannel"
ref="somePojo" method="someMethod"/&gt;</programlisting>
If no "output-channel" is available, it will then check the Message's <literal>RETURN_ADDRESS</literal> header
value. If that value is available, it will then check its type. If it is a
<interfacename>MessageChannel</interfacename>, the reply message will be sent to that channel. If it is a
<classname>String</classname>, then the endpoint will attempt to resolve the channel name to a channel instance.
If the channel cannot be resolved, then a <classname>ChannelResolutionException</classname> will be thrown.
</para>
</section>
</chapter>