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This is a significant update to the build system, including the changes listed below. README.md has been updated with instructions on the most important day-to-day commands. - Eliminate buildSrc submodule In favor of using the new bundlor and docbook-reference plugins. The net effect is a large reduction in number of lines of build code. Common docbook resources, stylesheets, etc are stored directly in the docbook plugin. This means that --recursive is no longer required when cloning and there will never be a need to use `git submodule` commands. README files have been updated to reflect. Use of the new bundlor plugin also means the removal of template.mf files from the source tree in favor of an inline approach. See build.gradle for details. Bundlor 'import templates' are built up programmatically and kept physically close to gradle dependency declarations, leading to more convenience when changing these values and hopefully fewer errors / version inconsistencies over time. Certain tests depended on the presence of template.mf files, all of which have recently been removed from the source tree in favor of the new bundlor plugin which allows for inlining bundlor configuration within the Gradle build script. These tests now create temp files using the java.io.File API instead. - Upgrade to Gradle 1.0-milestone-6 The m6 release is significantly faster when resolving dependencies and has a number of valuable new features over the earlier m3 version. Review the release notes for Gradle 1.0-milestone-6 online for full details. - Switch to repo.springsource.org repository Previously the project build declared as many repositories as necessary to resolve all project dependencies. Now depending on a single 'virtual repository' defined within the SpringSource Artifactory instance at http://repo.springsource.org. Currently, the virtual repository in use is 'libs-milestone', which allows for the resolution of all "milestone-or-better" versions of all S2 and third-party dependencies. Should snapshot dependencies become required, this value may be changed from 'libs-milestone' to 'libs-snapshot'. To build only against GA releases, change the value to 'libs-release'. - New build plan(s) Spring Integration build plans have been updated to use the Artifactory Bamboo plugin and publish to repo.springsource.org. Build plans have names like 2.1.x to reflect the version under development, not necessarily the name of the branch, as this may change over time and across major releases. - Improve release process As mentioned above, Spring Integration will now use the Artifactory Bamboo plugin to publish releases and also use Artifactory's support for pushing builds directly into Maven Central via oss.sonatype.org. Generate poms that contain all necessary fields for onboarding at Maven central (scm, developers, organization, licenses, etc). Generate -source and -javadoc poms to comply with Maven Central onboarding rules (and for general good practice anyway). Generation of PGP signatures, sha1 and md5 checksums are all handled automatically by Artifactory. These are also requirements for automated entry into Maven Central. - Remove source-level pom generation Automatic generation of Maven poms suitable for use in building Spring Integration is no longer supported. Generation and publication of poms for the purpose of dependency management remains supported. Sonar support has to date depended on these poms, but will be switched over to use the Gradle Sonar plugin shortly. - Eliminate docs subproject Move docs/src to the root of the project and eliminate docs as a formal subproject. This simplifies the build in a number of ways, including removing the need for distinguishing between 'subprojects' and 'javaprojects' as well as allowing users to build both 'api' and 'reference' docs without qualifying with a ':docs' prefix. Also rename the src/info directory to src/dist to better reflect that these files are packaged with the distribution. For example, the readme.txt there is really the distribution readme, distinct from the README.md at the root of the project which is for building from source, etc.
60 lines
3.5 KiB
XML
60 lines
3.5 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<section xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="bridge"
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xmlns:xlink="http://www.w3.org/1999/xlink">
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<title>Messaging Bridge</title>
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<section id="bridge-introduction">
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<title>Introduction</title>
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<para>
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A Messaging Bridge is a relatively trivial endpoint that simply connects two Message Channels or Channel
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Adapters. For example, you may want to connect a <interfacename>PollableChannel</interfacename> to a
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<interfacename>SubscribableChannel</interfacename> so that the subscribing endpoints do not have to worry
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about any polling configuration. Instead, the Messaging Bridge provides the polling configuration.
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</para>
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<para>
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By providing an intermediary poller between two channels, a Messaging Bridge can be used to throttle inbound
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Messages. The poller's trigger will determine the rate at which messages arrive on the second channel, and the
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poller's "maxMessagesPerPoll" property will enforce a limit on the throughput.
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</para>
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<para>
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Another valid use for a Messaging Bridge is to connect two different systems. In such a scenario, Spring
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Integration's role would be limited to making the connection between these systems and managing a poller
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if necessary. It is probably more common to have at least a <emphasis>Transformer</emphasis> between the
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two systems to translate between their formats, and in that case, the channels would be provided as the
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'input-channel' and 'output-channel' of a Transformer endpoint. If data format translation is not required,
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the Messaging Bridge may indeed be sufficient.
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</para>
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</section>
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<section id="bridge-namespace">
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<title>Configuring Bridge</title>
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<para>
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The <bridge> element is used to create a Messaging Bridge between two Message Channels or Channel Adapters.
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Simply provide the "input-channel" and "output-channel" attributes:
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<programlisting language="xml"><![CDATA[ <int:bridge input-channel="input" output-channel="output"/>]]></programlisting>
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As mentioned above, a common use case for the Messaging Bridge is to connect a
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<interfacename>PollableChannel</interfacename> to a <interfacename>SubscribableChannel</interfacename>, and when
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performing this role, the Messaging Bridge may also serve as a throttler:
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<programlisting language="xml"><![CDATA[ <int:bridge input-channel="pollable" output-channel="subscribable">
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<int:poller max-messages-per-poll="10" fixed-rate="5000"/>
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</int:bridge>]]></programlisting>
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</para>
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<para>
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Connecting Channel Adapters is just as easy. Here is a simple echo example between the "stdin" and "stdout"
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adapters from Spring Integration's "stream" namespace.
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<programlisting language="xml"><![CDATA[ <int-stream:stdin-channel-adapter id="stdin"/>
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<int-stream:stdout-channel-adapter id="stdout"/>
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<int:bridge id="echo" input-channel="stdin" output-channel="stdout"/>]]></programlisting>
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Of course, the configuration would be similar for other (potentially more useful) Channel Adapter bridges, such
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as File to JMS, or Mail to File. The various Channel Adapters will be discussed in upcoming chapters.
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</para>
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<note>
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<para>If no 'output-channel' is defined on a bridge, the reply channel provided by the inbound Message will
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be used, if available. If neither output or reply channel is available, an Exception will be thrown.</para>
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</note>
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</section>
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</section>
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