06831b9e22
For reference see: https://jira.springsource.org/browse/INT-2882 * Verify spacing * Ensure all source code samples are typed: e.g. <programlisting language="xml"> * Ensure source code fits space in PDF format
49 lines
2.9 KiB
XML
49 lines
2.9 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<section version="5.0" xml:id="control-bus"
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xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:ns5="http://www.w3.org/1999/xhtml"
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xmlns:ns4="http://www.w3.org/1998/Math/MathML"
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xmlns:ns3="http://www.w3.org/2000/svg"
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xmlns:ns="http://docbook.org/ns/docbook">
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<title>Control Bus</title>
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<para>As described in (EIP), the idea behind the Control Bus is that the
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same messaging system can be used for monitoring and managing the components
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within the framework as is used for "application-level" messaging. In Spring
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Integration we build upon the adapters described above so that it's possible
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to send Messages as a means of invoking exposed operations.</para>
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<programlisting language="xml"><int:control-bus input-channel="operationChannel"/></programlisting>
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<para>The Control Bus has an input channel that can be accessed for invoking
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operations on the beans in the application context. It also has all the
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common properties of a service activating endpoint, e.g. you can specify an
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output channel if the result of the operation has a return value that you
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want to send on to a downstream channel.</para>
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<para>The Control Bus executes messages on the input channel as Spring
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Expression Language expressions. It takes a message, compiles the body to an
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expression, adds some context, and then executes it. The default context
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supports any method that has been annotated with @ManagedAttribute or @ManagedOperation.
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It also supports the methods on Spring's Lifecycle interface, and it supports methods
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that are used to configure several of Spring's TaskExecutor and TaskScheduler implementations.
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The simplest way to ensure that your own methods are available to the Control Bus is to
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use the @ManagedAttribute and/or @ManagedOperation annotations. Since those are also used
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for exposing methods to a JMX MBean registry, it's a convenient by-product (often the same
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types of operations you want to expose to the Control Bus would be reasonable for exposing
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via JMS). Resolution of any particular instance within the application context is achieved
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in the typical SpEL syntax. Simply provide the bean name with the SpEL prefix for beans (@).
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For example, to execute a method on a Spring Bean a client
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could send a message to the operation channel as follows:</para>
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<programlisting language="java"><![CDATA[Message operation = MessageBuilder.withPayload("@myServiceBean.shutdown()").build();
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operationChannel.send(operation)]]></programlisting>
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<para>The root of the context for the expression is the
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<classname>Message</classname> itself, so you also have access to the 'payload'
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and 'headers' as variables within your expression. This is consistent with all the other expression
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support in Spring Integration endpoints.</para>
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</section>
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