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Added documentation for the 'bridge' element (INT-486)

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Mark Fisher
2008-11-24 01:54:50 +00:00
parent b16431e265
commit 039c124dad
3 changed files with 61 additions and 2 deletions
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58
spring-integration-reference/src/bridge.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="bridge">
<title>Messaging Bridge</title>
<section id="bridge-introduction">
<title>Introduction</title>
<para>
A Messaging Bridge is a relatively trivial endpoint that simply connects two Message Channels or Channel
Adapters. For example, you may want to connect a <interfacename>PollableChannel</interfacename> to a
<interfacename>SubscribableChannel</interfacename> so that the subscribing endpoints do not have to worry
about any polling configuration. Instead, the Messaging Bridge provides the polling configuration.
</para>
<para>
By providing an intermediary poller between two channels, a Messaging Bridge can be used to throttle inbound
Messages. The poller's trigger will determine the rate at which messages arrive on the second channel, and the
poller's "maxMessagesPerPoll" property will enforce a limit on the throughput.
</para>
<para>
Another valid use for a Messaging Bridge is to connect two different systems. In such a scenario, Spring
Integration's role would be limited to making the connection between these systems and managing a poller
if necessary. It is probably more common to have at least a <emphasis>Transformer</emphasis> between the
two systems to translate between their formats, and in that case, the channels would be provided as the
'input-channel' and 'output-channel' of a Transformer endpoint. If data format translation is not required,
the Messaging Bridge may indeed be sufficient.
</para>
</section>
<section id="bridge-namespace">
<title>The &lt;bridge&gt; Element</title>
<para>
The &lt;bridge&gt; element is used to create a Messaging Bridge between two Message Channels or Channel Adapters.
Simply provide the "input-channel" and "output-channel" attributes:
<programlisting language="xml"><![CDATA[ <bridge input-channel="input" output-channel="output"/>]]></programlisting>
As mentioned above, a common use case for the Messaging Bridge is to connect a
<interfacename>PollableChannel</interfacename> to a <interfacename>SubscribableChannel</interfacename>, and when
performing this role, the Messaging Bridge may also serve as a throttler:
<programlisting language="xml"><![CDATA[ <bridge input-channel="pollable" output-channel="subscribable">
<poller max-messages-per-poll="10">
<interval-trigger interval="5" time-unit="SECONDS"/>
</poller>
</bridge>]]></programlisting>
</para>
<para>
Connecting Channel Adapters is just as easy. Here is a simple echo example between the "stdin" and "stdout"
adapters from Spring Integration's "stream" namespace.
<programlisting language="xml"><![CDATA[ <stream:stdin-channel-adapter id="stdin"/>
<stream:stdout-channel-adapter id="stdout"/>
<bridge id="echo" input-channel="stdin" output-channel="stdout"/>]]></programlisting>
Of course, the configuration would be similar for other (potentially more useful) Channel Adapter bridges, such
as File to JMS, or Mail to File. The various Channel Adapters will be discussed in upcoming chapters.
</para>
</section>
</chapter>

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spring-integration-reference/src/spring-integration-reference.xml
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<xi:include href="./aggregator.xml"/>
<xi:include href="./resequencer.xml"/>
<xi:include href="./gateway.xml"/>
<xi:include href="./bridge.xml"/>
<xi:include href="./file.xml"/>
<xi:include href="./jms.xml"/>
<xi:include href="./ws.xml"/>

4
spring-integration-reference/src/stream.xml
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@@ -41,8 +41,8 @@
<classname>OutputStream</classname> for byte streams or <classname>Writer</classname> for character streams,
and each provides a second constructor that adds the optional 'bufferSize'. Since both of these
ultimately implement the <interfacename>MessageHandler</interfacename> interface, they can be referenced from a
<emphasis>channel-adapter</emphasis> configuration as will be described in more detail in
<xref linkend="namespace-endpoint"/>.
<emphasis>channel-adapter</emphasis> configuration as described in more detail in
<xref linkend="channel-adapter"/>.
<programlisting language="xml"><![CDATA[<bean class="org.springframework.integration.stream.ByteStreamWritingMessageHandler">
<constructor-arg ref="someOutputStream"/>
<constructor-arg value="1024"/>