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This commit is contained in:
Iwein Fuld
2009-04-14 17:20:51 +00:00
parent 33787588ab
commit bde9178a1f
2 changed files with 54 additions and 23 deletions
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spring-integration-reference/src/chain.xml
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@@ -26,8 +26,20 @@
</tip>
</para>
<para>
The handler chain simplifies configuration while internally maintaining the same degree of loose coupling between
components, and it is trivial to modify the configuration if at some point a non-linear arrangement is required.
The handler chain simplifies configuration while internally maintaining the same degree of loose coupling between
components, and it is trivial to modify the configuration if at some point a non-linear arrangement is required.
The chain will be expanded into a linear setup of the listed endpoints, separated by direct
channels. The reply channel header will not be taken into account within the chain: only
after the last handler is invoked will the resulting message be forwarded onto the reply channel or the chain's output
channel. Because of this setup all handlers except the last require a <methodname>setOutputChannel</methodname>
implementation. The last handler only needs an output channel if the outputChannel on the MessageHandlerChain is set.
If this is not the case, the "replyChannel" header needs to be set on each message, so that it is clear where the
message needs to go.
</para>
<para>
In most cases there is no need to implement MessageHandlers yourself. The next section will focus on namespace
support for the chain element. Most Spring Integration enpoints like Service Activators and Transformers are
suitable for use within a <classname>MessageHandlerChain</classname>.
</para>
</section>
@@ -36,7 +48,7 @@
<para>
The &lt;chain&gt; element provides an 'input-channel' attribute, and if the last element in the chain is capable
of producing reply messages, it may optionally provide an 'output-channel' attribute. The sub-elements are then
filters, transformers, splitters, and service-activators. The last element may be a router.
filters, transformers, splitters, and service-activators. The last element may also be a router or aggregator.
<programlisting language="xml"><![CDATA[ <chain input-channel="input" output-channel="output">
<filter ref="someSelector" throw-exception-on-rejection="true"/>
<header-enricher error-channel="customErrorChannel">
@@ -45,7 +57,9 @@
<service-activator ref="someService" method="someMethod"/>
</chain>]]></programlisting>
</para>
The &lt;header-enricher&gt; used in the above example will set a message header with name "foo" and value "bar" on the message.
The &lt;header-enricher&gt; element used in the above example will set a message header with name "foo" and value "bar" on the message.
A header enricher is a specialization of Transformer that touches only header values. You could obtain the same result by
implementing a MessageHandler that did the header modifications and wiring that as a bean.
</section>
</chapter>