INT-1605 updated aggregator documentatio to reflect new attributes, added more SpEL samples for aggregator's release-strategy-expression as well as correlation-strategy-expression
This commit is contained in:
Oleg Zhurakousky
@@ -305,28 +305,38 @@
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<para>Spring Integration supports the configuration of an aggregator via
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XML through the <aggregator/> element. Below you can see an example
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of an aggregator with all optional parameters defined.</para>
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of an aggregator.</para>
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<programlisting lang="xml"><![CDATA[<channel id="inputChannel"/>
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<aggregator id="completelyDefinedAggregator" ]]><co id="aggxml1" /><![CDATA[
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input-channel="inputChannel" ]]><co id="aggxml2" /><![CDATA[
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output-channel="outputChannel" ]]><co id="aggxml3" /><![CDATA[
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discard-channel="discardChannel" ]]><co id="aggxml4" /><![CDATA[
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ref="aggregatorBean" ]]><co id="aggxml5" /><![CDATA[
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method="add" ]]><co id="aggxml6" /><![CDATA[
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release-strategy="releaseStrategyBean" ]]><co id="aggxml7" /><![CDATA[
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release-strategy-method="canRelease" ]]><co id="aggxml8" /><![CDATA[
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correlation-strategy="correlationStrategyBean" ]]><co
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id="aggxmlCorrelationStrategy" /><![CDATA[
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correlation-strategy-method="groupNumbersByLastDigit" ]]><co
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id="aggxmlCorrelationStrategyMethod" /><![CDATA[
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message-store="messageStore" ]]><co id="aggxml11-co" linkends="aggxml11" /><![CDATA[
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send-partial-result-on-expiry="true" ]]><co id="aggxml9" /><![CDATA[
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send-timeout="86420000" ]]><co id="aggxml10" /><![CDATA[
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expression="#this.toArray()" ]]><co id="aggxml12" /><![CDATA[/>
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<channel id="outputChannel"/>
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<int:aggregator id="myAggregator" ]]><co id="aggxml01" /><![CDATA[
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auto-startup="true" ]]><co id="aggxml02" /><![CDATA[
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input-channel="inputChannel" ]]><co id="aggxml03" /><![CDATA[
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output-channel="outputChannel" ]]><co id="aggxml04" /><![CDATA[
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discard-channel="throwAwayChannel" ]]><co id="aggxml05" /><![CDATA[
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message-store="persistentMessageStore" ]]><co id="aggxml06" /><![CDATA[
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order="1" ]]><co id="aggxml07" /><![CDATA[
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send-partial-result-on-expiry="false" ]]><co id="aggxml08" /><![CDATA[
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send-timeout="1000" ]]><co id="aggxml09" /><![CDATA[
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correlation-strategy="correlationStrategyBean" ]]><co id="aggxml10" /><![CDATA[
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correlation-strategy-method="correlate" ]]><co id="aggxml11" /><![CDATA[
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ref="aggregatorBean" ]]><co id="aggxml12" /><![CDATA[
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method="aggregate" ]]><co id="aggxml13" /><![CDATA[
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release-strategy="releaseStrategyBean" ]]><co id="aggxml14" /><![CDATA[
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release-strategy-method="release"/> ]]><co id="aggxml15" /><![CDATA[
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<int:channel id="outputChannel"/>
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<int:channel id="throwAwayChannel"/>
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<bean id="nessageStore" class="org.springframework.integration.jdbc.JdbcMessageStore">
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<constructor-arg ref="dataSource"/>
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</bean>
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<bean id="aggregatorBean" class="sample.PojoAggregator"/>
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@@ -335,96 +345,103 @@
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<bean id="correlationStrategyBean" class="sample.PojoCorrelationStrategy"/>]]></programlisting>
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<calloutlist>
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<callout arearefs="aggxml1">
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<callout arearefs="aggxml01">
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<para>The id of the aggregator is
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<emphasis>optional</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml2">
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<para>The input channel of the aggregator.
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<callout arearefs="aggxml02">
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<para>Lifecycle attribute signaling if aggregator should be started during Application Context startup.
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<emphasis>Optional (default is 'true')</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml03">
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<para>The channel where aggregator will receive messages from
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<emphasis>Required</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml3">
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<callout arearefs="aggxml04">
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<para>The channel where the aggregator will send the aggregation
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results. <emphasis>Optional (because incoming messages can specify a
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reply channel themselves)</emphasis>.</para>
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reply channel themselves via 'replyChannel' Message Header)</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml4">
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<callout arearefs="aggxml05">
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<para>The channel where the aggregator will send the messages that
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timed out (if <code>send-partial-results-on-timeout</code> is
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timed out (if <code>send-partial-results-on-expiry</code> is
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<emphasis>false</emphasis>). <emphasis>Optional</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml5">
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<para>A reference to a bean defined in the application context. The
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bean must implement the aggregation logic as described above.
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<emphasis>Required</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml6">
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<para>A method defined on the bean referenced by <code>ref</code>,
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<emphasis>that implements the message aggregation
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algorithm.</emphasis> <emphasis>Optional, with restrictions (see
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above).</emphasis></para>
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</callout>
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<callout arearefs="aggxml7">
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<para>A reference to a bean that implements the decision algorithm as
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to whether a given message group is complete. The bean can be an
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implementation of the CompletionStrategy interface or a POJO. In the
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latter case the completion-strategy-method attribute must be defined
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as well. <emphasis>Optional (by default, the aggregator will use
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sequence size) </emphasis>.</para>
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</callout>
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<callout arearefs="aggxml8">
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<para>A method defined on the bean referenced by
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<code>release-strategy</code>, <emphasis>that implements the
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completion decision algorithm.</emphasis> <emphasis>Optional, with
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restrictions (requires <code>completion-strategy</code> to be
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present).</emphasis></para>
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</callout>
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<callout arearefs="aggxmlCorrelationStrategy">
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<para>A reference to a bean that implements the correlation strategy.
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The bean can be an implementation of the CorrelationStrategy interface
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or a POJO. In the latter case the correlation-strategy-method
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attribute must be defined as well. <emphasis>Optional (by default, the
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aggregator will use the correlation id header attribute)
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</emphasis>.</para>
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</callout>
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<callout arearefs="aggxmlCorrelationStrategyMethod">
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<para>A method defined on the bean referenced by
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<code>correlation-strategy</code>, <emphasis>that implements the
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correlation key algorithm.</emphasis> <emphasis>Optional, with
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restrictions (requires <code>correlation-strategy</code> to be
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present).</emphasis></para>
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</callout>
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<callout arearefs="aggxml11-co" id="aggxml11">
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<callout arearefs="aggxml06">
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<para>A reference to a <code>MessageGroupStore</code> that can be used
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to store groups of messages under their correlation key until they are
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complete. <emphasis>Optional</emphasis> with default a volatile
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in-memory store.</para>
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</callout>
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<callout arch="" arearefs="aggxml9">
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<para>Whether upon the expiration of the message group, the aggregator
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will try to aggregate the messages that have already arrived.
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<emphasis>Optional (false by default)</emphasis>.</para>
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<callout arearefs="aggxml07">
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<para>Order of this aggregator in when more then one aggregator is subscribig to the same DirectChannel
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(use for load balancing purposes)
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<emphasis>Optional</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml10">
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<callout arearefs="aggxml08">
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<para>Tells if partially aggregated messages should be released when their storage time had expired
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(see MessageGroupStore.expireMessageGroups(long))
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<emphasis>Optional</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml09">
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<para>The timeout for sending the aggregated messages to the output or
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reply channel. <emphasis>Optional</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml12">
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<para>SpEL expression to handle release strategy <emphasis>Optional</emphasis>.</para>
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<callout arearefs="aggxml10">
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<para>A reference to a bean that implements the decision algorithm as
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to whether a given message group is complete. The bean can be an
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implementation of the CorrelationStrategy interface or a POJO. In the
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latter case the correlation-strategy-method attribute must be defined
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as well. <emphasis>Optional (by default, the aggregator will use
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sequence size) </emphasis>.</para>
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</callout>
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<callout arearefs="aggxml11">
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<para>A method defined on the bean referenced by
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<code>correlation-strategy</code>, <emphasis>that implements the
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correlation decision algorithm.</emphasis> <emphasis>Optional, with
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restrictions (requires <code>correlation-strategy</code> to be
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present).</emphasis></para>
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</callout>
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<callout arearefs="aggxml12">
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<para>A reference to a bean defined in the application context. The bean must implement the aggregation logic
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as described above.<emphasis>Optional (by default the list of aggregated Messages will become a
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payload of the output message).</emphasis></para>
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</callout>
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<callout arearefs="aggxml13">
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<para>A method defined on the bean referenced by <code>ref</code>,
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<emphasis>that implements the message aggregation
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algorithm.</emphasis> <emphasis>Optional, depends on <code>ref</code> attribute being defined.</emphasis></para>
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</callout>
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<callout arearefs="aggxml14">
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<para>A reference to a bean that implements the release strategy.
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The bean can be an implementation of the <classname>ReleaseStrategy</classname> interface
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or a POJO. In the latter case the release-strategy-method
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attribute must be defined as well. <emphasis>Optional (by default, the
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aggregator will use the correlation id header attribute)
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</emphasis>.</para>
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</callout>
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<callout arearefs="aggxml15">
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<para>A method defined on the bean referenced by
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<code>release-strategy</code>, <emphasis>that implements the
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completion decision algorithm.</emphasis> <emphasis>Optional, with
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restrictions (requires <code>release-strategy</code> to be
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present).</emphasis></para>
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</callout>
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</calloutlist>
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<para>Using a "ref" attribute is generally recommended if a custom
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@@ -529,6 +546,34 @@
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assemble a new collection from the payloads of all messages in the list and then transforming it to an Array, thus
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achieving the same result as the java code above.
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</para>
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<para>
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The same expression-based approach could be applied when dealing with custom <emphasis>Release</emphasis> and
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<emphasis>Correlation</emphasis> strategies.
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Instead of defining a bean for custom <classname>CorrelationStrategy</classname> via <code>correlation-strategy</code>
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attribute you can implement your simple correlation logic via SpEL expression and configure it via
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<code>correlation-strategy-ecpression</code> attribute.
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</para>
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<para>
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For example:
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<programlisting language="xml"><![CDATA[correlation-strategy-expression="payload.getPerson().getId()"]]></programlisting>
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In the above example it is assumed that the payload has an attribute <code>person</code> with an <code>id</code>
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which is going to be used to correlate messages.
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</para>
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<para>
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And when it comes to <classname>ReleaseStrategy</classname> you can implement your release logic via
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SpEL expression as well and configure it via <code>release-strategy-expression</code> attribute.
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</para>
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<para>
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For example:
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<programlisting language="xml"><![CDATA[release-strategy-expression="payload.size() > 5"]]></programlisting>
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In this example the root of SpEL Evaluation Context is <classname>MessageGroup</classname> and you simply stating
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that as soon as there are more then 5 messages in this group release the group.
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</para>
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</section>
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<section>
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