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From conflue...@apache.org
Subject [CONF] Apache Camel > Aggregator2
Date Thu, 01 Mar 2012 10:37:00 GMT
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    <h2><a href="https://cwiki.apache.org/confluence/display/CAMEL/Aggregator2">Aggregator2</a></h2>
    <h4>Page <b>edited</b> by             <a href="https://cwiki.apache.org/confluence/display/~davsclaus">Claus
Ibsen</a>
    </h4>
        <br/>
                         <h4>Changes (1)</h4>
                                 
    
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                    <table class="diff" cellpadding="0" cellspacing="0">
    
            <tr><td class="diff-snipped" >...<br></td></tr>
            <tr><td class="diff-unchanged" >| forceCompletionOnStop | {{false}}
| *Camel 2.9* Indicates to complete all current aggregated exchanges when the context is stopped
|   <br>| eagerCheckCompletion | {{false}} | Whether or not to eager check for completion
when a new incoming [Exchange] has been received. This option influences the behavior of the
{{completionPredicate}} option as the [Exchange] being passed in changes accordingly. When
{{false}} the [Exchange] passed in the [Predicate] is the _aggregated_ Exchange which means
any information you may store on the aggregated Exchange from the {{AggregationStrategy}}
is available for the [Predicate]. When {{true}} the [Exchange] passed in the [Predicate] is
the _incoming_ [Exchange], which means you can access data from the incoming Exchange. | <br></td></tr>
            <tr><td class="diff-changed-lines" >| groupExchanges | {{false}} |
If enabled then Camel will group all aggregated Exchanges into a single combined {{org.apache.camel.impl.GroupedExchange}}
holder class that holds all the aggregated Exchanges. And as a result only one Exchange is
being sent out from the aggregator. Can be used to combine many incoming Exchanges into a
single output Exchange without coding a custom {{AggregationStrategy}} yourself. <span
class="diff-added-words"style="background-color: #dfd;">*Important:* This option does *not*
support persistant repository with the aggregator.</span> | <br></td></tr>
            <tr><td class="diff-unchanged" >| ignoreInvalidCorrelationKeys | {{false}}
| Whether or not to ignore correlation keys which could not be evaluated to a value. By default
Camel will throw an Exception, but you can enable this option and ignore the situation instead.
| <br>| closeCorrelationKeyOnCompletion |  | Whether or not too _late_ Exchanges should
be accepted or not. You can enable this to indicate that if a correlation key has already
been completed, then any new exchanges with the same correlation key be denied. Camel will
then throw a {{closedCorrelationKeyException}} exception. When using this option you pass
in a {{integer}} which is a number for a LRUCache which keeps that last X number of closed
correlation keys. You can pass in 0 or a negative value to indicate a unbounded cache. By
passing in a number you are ensured that cache won&#39;t grow too big if you use a log
of different correlation keys. | <br></td></tr>
            <tr><td class="diff-snipped" >...<br></td></tr>
    
            </table>
    </div>                            <h4>Full Content</h4>
                    <div class="notificationGreySide">
        <h3><a name="Aggregator2-Aggregator"></a>Aggregator</h3>

<p><b>This applies for Camel version 2.3 or newer. If you use an older version
then use this <a href="/confluence/display/CAMEL/Aggregator" title="Aggregator">Aggregator</a>
link instead.</b></p>

<p>The <a href="http://www.enterpriseintegrationpatterns.com/Aggregator.html" class="external-link"
rel="nofollow">Aggregator</a> from the <a href="/confluence/display/CAMEL/Enterprise+Integration+Patterns"
title="Enterprise Integration Patterns">EIP patterns</a> allows you to combine a
number of messages together into a single message. </p>

<p><span class="image-wrap" style=""><img src="http://www.enterpriseintegrationpatterns.com/img/Aggregator.gif"
style="border: 0px solid black" /></span></p>

<p>A correlation <a href="/confluence/display/CAMEL/Expression" title="Expression">Expression</a>
is used to determine the messages which should be aggregated together. If you want to aggregate
all messages into a single message, just use a constant expression. An AggregationStrategy
is used to combine all the message exchanges for a single correlation key into a single message
exchange. </p>

<h3><a name="Aggregator2-Aggregatoroptions"></a>Aggregator options</h3>
<p>The aggregator supports the following options:</p>
<div class="confluenceTableSmall"><div class='table-wrap'>
<table class='confluenceTable'><tbody>
<tr>
<th class='confluenceTh'> Option </th>
<th class='confluenceTh'> Default </th>
<th class='confluenceTh'> Description </th>
</tr>
<tr>
<td class='confluenceTd'> correlationExpression </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> Mandatory <a href="/confluence/display/CAMEL/Expression"
title="Expression">Expression</a> which evaluates the correlation key to use for
aggregation. The <a href="/confluence/display/CAMEL/Exchange" title="Exchange">Exchange</a>
which has the same correlation key is aggregated together. If the correlation key could not
be evaluated an Exception is thrown. You can disable this by using the <tt>ignoreBadCorrelationKeys</tt>
option. </td>
</tr>
<tr>
<td class='confluenceTd'> aggregationStrategy </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> Mandatory <tt>AggregationStrategy</tt> which is
used to <em>merge</em> the incoming <a href="/confluence/display/CAMEL/Exchange"
title="Exchange">Exchange</a> with the existing already merged exchanges. At first
call the <tt>oldExchange</tt> parameter is <tt>null</tt>. On subsequent
invocations the <tt>oldExchange</tt> contains the merged exchanges and <tt>newExchange</tt>
is of course the new incoming Exchange. </td>
</tr>
<tr>
<td class='confluenceTd'> strategyRef </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> A reference to lookup the <tt>AggregationStrategy</tt>
in the <a href="/confluence/display/CAMEL/Registry" title="Registry">Registry</a>.
</td>
</tr>
<tr>
<td class='confluenceTd'> completionSize </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> Number of messages aggregated before the aggregation is complete.
This option can be set as either a fixed value or using an <a href="/confluence/display/CAMEL/Expression"
title="Expression">Expression</a> which allows you to evaluate a size dynamically
- will use <tt>Integer</tt> as result. If both are set Camel will fallback to
use the fixed value if the <a href="/confluence/display/CAMEL/Expression" title="Expression">Expression</a>
result was <tt>null</tt> or <tt>0</tt>. </td>
</tr>
<tr>
<td class='confluenceTd'> completionTimeout </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> Time in millis that an aggregated exchange should be inactive
before its complete. This option can be set as either a fixed value or using an <a href="/confluence/display/CAMEL/Expression"
title="Expression">Expression</a> which allows you to evaluate a timeout dynamically
- will use <tt>Long</tt> as result. If both are set Camel will fallback to use
the fixed value if the <a href="/confluence/display/CAMEL/Expression" title="Expression">Expression</a>
result was <tt>null</tt> or <tt>0</tt>. You cannot use this option
together with completionInterval, only one of the two can be used. </td>
</tr>
<tr>
<td class='confluenceTd'> completionInterval </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> A repeating period in millis by which the aggregator will
complete all current aggregated exchanges. Camel has a background task which is triggered
every period. You cannot use this option together with completionTimeout, only one of them
can be used. </td>
</tr>
<tr>
<td class='confluenceTd'> completionPredicate </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> A <a href="/confluence/display/CAMEL/Predicate" title="Predicate">Predicate</a>
to indicate when an aggregated exchange is complete. </td>
</tr>
<tr>
<td class='confluenceTd'> completionFromBatchConsumer </td>
<td class='confluenceTd'> <tt>false</tt> </td>
<td class='confluenceTd'> This option is if the exchanges are coming from a <a href="/confluence/display/CAMEL/Batch+Consumer"
title="Batch Consumer">Batch Consumer</a>. Then when enabled the <a href="/confluence/display/CAMEL/Aggregator2"
title="Aggregator2">Aggregator2</a> will use the batch size determined by the <a
href="/confluence/display/CAMEL/Batch+Consumer" title="Batch Consumer">Batch Consumer</a>
in the message header <tt>CamelBatchSize</tt>. See more details at <a href="/confluence/display/CAMEL/Batch+Consumer"
title="Batch Consumer">Batch Consumer</a>. This can be used to aggregate all files
consumed from a <a href="/confluence/display/CAMEL/File2" title="File2">File</a>
endpoint in that given poll. </td>
</tr>
<tr>
<td class='confluenceTd'> forceCompletionOnStop </td>
<td class='confluenceTd'> <tt>false</tt> </td>
<td class='confluenceTd'> <b>Camel 2.9</b> Indicates to complete all current
aggregated exchanges when the context is stopped </td>
</tr>
<tr>
<td class='confluenceTd'> eagerCheckCompletion </td>
<td class='confluenceTd'> <tt>false</tt> </td>
<td class='confluenceTd'> Whether or not to eager check for completion when a new incoming
<a href="/confluence/display/CAMEL/Exchange" title="Exchange">Exchange</a> has
been received. This option influences the behavior of the <tt>completionPredicate</tt>
option as the <a href="/confluence/display/CAMEL/Exchange" title="Exchange">Exchange</a>
being passed in changes accordingly. When <tt>false</tt> the <a href="/confluence/display/CAMEL/Exchange"
title="Exchange">Exchange</a> passed in the <a href="/confluence/display/CAMEL/Predicate"
title="Predicate">Predicate</a> is the <em>aggregated</em> Exchange which
means any information you may store on the aggregated Exchange from the <tt>AggregationStrategy</tt>
is available for the <a href="/confluence/display/CAMEL/Predicate" title="Predicate">Predicate</a>.
When <tt>true</tt> the <a href="/confluence/display/CAMEL/Exchange" title="Exchange">Exchange</a>
passed in the <a href="/confluence/display/CAMEL/Predicate" title="Predicate">Predicate</a>
is the <em>incoming</em> <a href="/confluence/display/CAMEL/Exchange" title="Exchange">Exchange</a>,
which means you can access data from the incoming Exchange. </td>
</tr>
<tr>
<td class='confluenceTd'> groupExchanges </td>
<td class='confluenceTd'> <tt>false</tt> </td>
<td class='confluenceTd'> If enabled then Camel will group all aggregated Exchanges
into a single combined <tt>org.apache.camel.impl.GroupedExchange</tt> holder class
that holds all the aggregated Exchanges. And as a result only one Exchange is being sent out
from the aggregator. Can be used to combine many incoming Exchanges into a single output Exchange
without coding a custom <tt>AggregationStrategy</tt> yourself. <b>Important:</b>
This option does <b>not</b> support persistant repository with the aggregator.
</td>
</tr>
<tr>
<td class='confluenceTd'> ignoreInvalidCorrelationKeys </td>
<td class='confluenceTd'> <tt>false</tt> </td>
<td class='confluenceTd'> Whether or not to ignore correlation keys which could not
be evaluated to a value. By default Camel will throw an Exception, but you can enable this
option and ignore the situation instead. </td>
</tr>
<tr>
<td class='confluenceTd'> closeCorrelationKeyOnCompletion </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> Whether or not too <em>late</em> Exchanges should
be accepted or not. You can enable this to indicate that if a correlation key has already
been completed, then any new exchanges with the same correlation key be denied. Camel will
then throw a <tt>closedCorrelationKeyException</tt> exception. When using this
option you pass in a <tt>integer</tt> which is a number for a LRUCache which keeps
that last X number of closed correlation keys. You can pass in 0 or a negative value to indicate
a unbounded cache. By passing in a number you are ensured that cache won't grow too big if
you use a log of different correlation keys. </td>
</tr>
<tr>
<td class='confluenceTd'> discardOnCompletionTimeout </td>
<td class='confluenceTd'> <tt>false</tt> </td>
<td class='confluenceTd'> <b>Camel 2.5:</b> Whether or not exchanges which
complete due to a timeout should be discarded. If enabled then when a timeout occurs the aggregated
message will <b>not</b> be sent out but dropped (discarded). </td>
</tr>
<tr>
<td class='confluenceTd'> aggregationRepository </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> Allows you to plugin you own implementation of <tt>org.apache.camel.spi.AggregationRepository</tt>
which keeps track of the current inflight aggregated exchanges. Camel uses by default a memory
based implementation. </td>
</tr>
<tr>
<td class='confluenceTd'> aggregationRepositoryRef </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> Reference to lookup a <tt>aggregationRepository</tt>
in the <a href="/confluence/display/CAMEL/Registry" title="Registry">Registry</a>.
</td>
</tr>
<tr>
<td class='confluenceTd'> parallelProcessing </td>
<td class='confluenceTd'> <tt>false</tt> </td>
<td class='confluenceTd'> When aggregated are completed they are being send out of the
aggregator. This option indicates whether or not Camel should use a thread pool with multiple
threads for concurrency. If no custom thread pool has been specified then Camel creates a
default pool with 10 concurrent threads. </td>
</tr>
<tr>
<td class='confluenceTd'> executorService </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> If using <tt>parallelProcessing</tt> you can specify
a custom thread pool to be used. In fact also if you are not using <tt>parallelProcessing</tt>
this custom thread pool is used to send out aggregated exchanges as well. </td>
</tr>
<tr>
<td class='confluenceTd'> executorServiceRef </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> Reference to lookup a <tt>executorService</tt>
in the <a href="/confluence/display/CAMEL/Registry" title="Registry">Registry</a>
</td>
</tr>
<tr>
<td class='confluenceTd'> timeoutCheckerExecutorService </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> <b>Camel 2.9:</b> If using either of the <tt>completionTimeout</tt>,
<tt>completionTimeoutExpression</tt>, or <tt>completionInterval</tt>
options a background thread is created to check for the completion for every aggregator. Set
this option to provide a custom thread pool to be used rather than creating a new thread for
every aggregator. </td>
</tr>
<tr>
<td class='confluenceTd'> timeoutCheckerExecutorServiceRef </td>
<td class='confluenceTd'>&nbsp;</td>
<td class='confluenceTd'> <b>Camel 2.9:</b> Reference to lookup a <tt>timeoutCheckerExecutorService</tt>
in the <a href="/confluence/display/CAMEL/Registry" title="Registry">Registry</a>
</td>
</tr>
</tbody></table>
</div>
</div>

<h3><a name="Aggregator2-ExchangeProperties"></a>Exchange Properties</h3>

<p>The following properties are set on each aggregated Exchange:</p>
<div class="confluenceTableSmall"><div class='table-wrap'>
<table class='confluenceTable'><tbody>
<tr>
<th class='confluenceTh'> header </th>
<th class='confluenceTh'> type </th>
<th class='confluenceTh'> description </th>
</tr>
<tr>
<td class='confluenceTd'> <tt>CamelAggregatedSize</tt> </td>
<td class='confluenceTd'> int </td>
<td class='confluenceTd'> The total number of Exchanges aggregated into this combined
Exchange. </td>
</tr>
<tr>
<td class='confluenceTd'> <tt>CamelAggregatedCompletedBy</tt> </td>
<td class='confluenceTd'> String </td>
<td class='confluenceTd'> Indicator how the aggregation was completed as a value of
either: <tt>predicate</tt>, <tt>size</tt>, <tt>consumer</tt>,
<tt>timeout</tt> or <tt>interval</tt>. </td>
</tr>
</tbody></table>
</div>
</div>

<h3><a name="Aggregator2-AboutAggregationStrategy"></a>About AggregationStrategy</h3>
<p>The <tt>AggregationStrategy</tt> is used for aggregating the old (lookup
by its correlation id) and the new exchanges together into a single exchange. Possible implementations
include performing some kind of combining or delta processing, such as adding line items together
into an invoice or just using the newest exchange and removing old exchanges such as for state
tracking or market data prices; where old values are of little use.</p>

<p>Notice the aggregation strategy is a mandatory option and must be provided to the
aggregator.</p>

<p>Here are a few example AggregationStrategy implementations that should help you create
your own custom strategy.</p>

<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">
<span class="code-comment">//simply combines Exchange <span class="code-object">String</span>
body values using '+' as a delimiter
</span>class StringAggregationStrategy <span class="code-keyword">implements</span>
AggregationStrategy {

    <span class="code-keyword">public</span> Exchange aggregate(Exchange oldExchange,
Exchange newExchange) {
        <span class="code-keyword">if</span> (oldExchange == <span class="code-keyword">null</span>)
{
            <span class="code-keyword">return</span> newExchange;
        }

        <span class="code-object">String</span> oldBody = oldExchange.getIn().getBody(<span
class="code-object">String</span>.class);
        <span class="code-object">String</span> newBody = newExchange.getIn().getBody(<span
class="code-object">String</span>.class);
        oldExchange.getIn().setBody(oldBody + <span class="code-quote">"+"</span>
+ newBody);
        <span class="code-keyword">return</span> oldExchange;
    }
}

<span class="code-comment">//simply combines Exchange body values into an ArrayList&lt;<span
class="code-object">Object</span>&gt;
</span>class ArrayListAggregationStrategy <span class="code-keyword">implements</span>
AggregationStrategy {

    <span class="code-keyword">public</span> Exchange aggregate(Exchange oldExchange,
Exchange newExchange) {
	<span class="code-object">Object</span> newBody = newExchange.getIn().getBody();
	ArrayList&lt;<span class="code-object">Object</span>&gt; list = <span
class="code-keyword">null</span>;
        <span class="code-keyword">if</span> (oldExchange == <span class="code-keyword">null</span>)
{
		list = <span class="code-keyword">new</span> ArrayList&lt;<span class="code-object">Object</span>&gt;();
		list.add(newBody);
		newExchange.getIn().setBody(list);
		<span class="code-keyword">return</span> newExchange;
        } <span class="code-keyword">else</span> {
	        list = oldExchange.getIn().getBody(ArrayList.class);
		list.add(newBody);
		<span class="code-keyword">return</span> oldExchange;
	}
    }
}
</pre>
</div></div>

<h3><a name="Aggregator2-Aboutcompletion"></a>About completion</h3>
<p>When aggregation <a href="/confluence/display/CAMEL/Exchange" title="Exchange">Exchange</a>s
at some point you need to indicate that the aggregated exchanges is complete, so they can
be send out of the aggregator. Camel allows you to indicate completion in various ways as
follows:</p>
<ul class="alternate" type="square">
	<li>completionTimeout - Is an inactivity timeout in which is triggered if no new exchanges
have been aggregated for that particular correlation key within the period.</li>
	<li>completionInterval - Once every X period all the current aggregated exchanges are
completed.</li>
	<li>completionSize - Is a number indicating that after X aggregated exchanges it's
complete.</li>
	<li>completionPredicate - Runs a <a href="/confluence/display/CAMEL/Predicate" title="Predicate">Predicate</a>
when a new exchange is aggregated to determine if we are complete or not</li>
	<li>completionFromBatchConsumer - Special option for <a href="/confluence/display/CAMEL/Batch+Consumer"
title="Batch Consumer">Batch Consumer</a> which allows you to complete when all the
messages from the batch has been aggregated.</li>
	<li>forceCompletionOnStop - <b>Camel 2.9</b> Indicates to complete all
current aggregated exchanges when the context is stopped</li>
</ul>


<p>Notice that all the completion ways are per correlation key. And you can combine
them in any way you like. It's basically the first which triggers that wins. So you can use
a completion size together with a completion timeout. Only completionTimeout and completionInterval
cannot be used at the same time.</p>

<p>Notice the completion is a mandatory option and must be provided to the aggregator.
If not provided Camel will thrown an Exception on startup.</p>

<h3><a name="Aggregator2-PersistentAggregationRepository"></a>Persistent
AggregationRepository</h3>
<p>The aggregator provides a pluggable repository which you can implement your own <tt>org.apache.camel.spi.AggregationRepository</tt>.<br/>
If you need persistent repository then you can use either Camel <a href="/confluence/display/CAMEL/HawtDB"
title="HawtDB">HawtDB</a> or <a href="/confluence/display/CAMEL/SQL+Component"
title="SQL Component">SQL Component</a> components.</p>

<h3><a name="Aggregator2-Examples"></a>Examples</h3>
<p>See some examples from the old <a href="/confluence/display/CAMEL/Aggregator"
title="Aggregator">Aggregator</a> which is somewhat similar to this new aggregator.</p>

<div class='panelMacro'><table class='tipMacro'><colgroup><col width='24'><col></colgroup><tr><td
valign='top'><img src="/confluence/images/icons/emoticons/check.gif" width="16" height="16"
align="absmiddle" alt="" border="0"></td><td><b>Setting options in Spring
XML</b><br />Many of the options are configurable as attributes on the <tt>&lt;aggregate&gt;</tt>
tag when using Spring XML.</td></tr></table></div>

<h4><a name="Aggregator2-UsingcompletionTimeout"></a>Using completionTimeout</h4>
<p>In this example we want to aggregate all incoming messages and after 3 seconds of
inactivity we want the aggregation to complete. This is done using the <tt>completionTimeout</tt>
option as shown:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">from(<span class="code-quote">"direct:start"</span>)
    <span class="code-comment">// aggregate all exchanges correlated by the id header.
</span>    <span class="code-comment">// Aggregate them using the BodyInAggregatingStrategy
strategy which
</span>    <span class="code-comment">// and after 3 seconds of inactivity them
timeout and complete the aggregation
</span>    <span class="code-comment">// and send it to mock:aggregated
</span>    .aggregate(header(<span class="code-quote">"id"</span>), <span
class="code-keyword">new</span> BodyInAggregatingStrategy()).completionTimeout(3000)
        .to(<span class="code-quote">"mock:aggregated"</span>);
</pre>
</div></div>

<p>And the same example using Spring XML:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-xml"><span class="code-tag">&lt;camelContext xmlns=<span
class="code-quote">"http://camel.apache.org/schema/spring"</span>&gt;</span>
    <span class="code-tag">&lt;route&gt;</span>
        <span class="code-tag">&lt;from uri=<span class="code-quote">"direct:start"</span>/&gt;</span>
        <span class="code-tag">&lt;aggregate strategyRef=<span class="code-quote">"aggregatorStrategy"</span>
completionTimeout=<span class="code-quote">"3000"</span>&gt;</span>
            <span class="code-tag">&lt;correlationExpression&gt;</span>
                <span class="code-tag">&lt;simple&gt;</span>header.id<span
class="code-tag">&lt;/simple&gt;</span>
            <span class="code-tag">&lt;/correlationExpression&gt;</span>
            <span class="code-tag">&lt;to uri=<span class="code-quote">"mock:aggregated"</span>/&gt;</span>
        <span class="code-tag">&lt;/aggregate&gt;</span>
    <span class="code-tag">&lt;/route&gt;</span>
<span class="code-tag">&lt;/camelContext&gt;</span>

<span class="code-tag">&lt;bean id=<span class="code-quote">"aggregatorStrategy"</span>
class=<span class="code-quote">"org.apache.camel.processor.BodyInAggregatingStrategy"</span>/&gt;</span>
</pre>
</div></div>

<h4><a name="Aggregator2-UsingcompletionSize"></a>Using completionSize</h4>
<p>In this example we want to aggregate all incoming messages and when we have 3 messages
aggregated (in the same correlation group) we want the aggregation to complete. This is done
using the <tt>completionSize</tt> option as shown:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">from(<span class="code-quote">"direct:start"</span>)
    <span class="code-comment">// aggregate all exchanges correlated by the id header.
</span>    <span class="code-comment">// Aggregate them using the BodyInAggregatingStrategy
strategy which
</span>    <span class="code-comment">// and after 3 messages has been aggregated
then complete the aggregation
</span>    <span class="code-comment">// and send it to mock:aggregated
</span>    .aggregate(header(<span class="code-quote">"id"</span>), <span
class="code-keyword">new</span> BodyInAggregatingStrategy()).completionSize(3)
        .to(<span class="code-quote">"mock:aggregated"</span>);
</pre>
</div></div>

<p>And the same example using Spring XML:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-xml"><span class="code-tag">&lt;camelContext xmlns=<span
class="code-quote">"http://camel.apache.org/schema/spring"</span>&gt;</span>
    <span class="code-tag">&lt;route&gt;</span>
        <span class="code-tag">&lt;from uri=<span class="code-quote">"direct:start"</span>/&gt;</span>
        <span class="code-tag">&lt;aggregate strategyRef=<span class="code-quote">"aggregatorStrategy"</span>
completionSize=<span class="code-quote">"3"</span>&gt;</span>
            <span class="code-tag">&lt;correlationExpression&gt;</span>
                <span class="code-tag">&lt;simple&gt;</span>header.id<span
class="code-tag">&lt;/simple&gt;</span>
            <span class="code-tag">&lt;/correlationExpression&gt;</span>
            <span class="code-tag">&lt;to uri=<span class="code-quote">"mock:aggregated"</span>/&gt;</span>
        <span class="code-tag">&lt;/aggregate&gt;</span>
    <span class="code-tag">&lt;/route&gt;</span>
<span class="code-tag">&lt;/camelContext&gt;</span>

<span class="code-tag">&lt;bean id=<span class="code-quote">"aggregatorStrategy"</span>
class=<span class="code-quote">"org.apache.camel.processor.BodyInAggregatingStrategy"</span>/&gt;</span>
</pre>
</div></div>

<h4><a name="Aggregator2-UsingcompletionPredicate"></a>Using completionPredicate</h4>
<p>In this example we want to aggregate all incoming messages and use a <a href="/confluence/display/CAMEL/Predicate"
title="Predicate">Predicate</a> to determine when we are complete. The <a href="/confluence/display/CAMEL/Predicate"
title="Predicate">Predicate</a> can be evaluated using either the aggregated exchange
(default) or the incoming exchange. We will so both situations as examples. We start with
the default situation as shown:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">from(<span class="code-quote">"direct:start"</span>)
    <span class="code-comment">// aggregate all exchanges correlated by the id header.
</span>    <span class="code-comment">// Aggregate them using the BodyInAggregatingStrategy
strategy which
</span>    <span class="code-comment">// and when the aggregated body contains
A+B+C then complete the aggregation
</span>    <span class="code-comment">// and send it to mock:aggregated
</span>    .aggregate(header(<span class="code-quote">"id"</span>), <span
class="code-keyword">new</span> BodyInAggregatingStrategy()).completionPredicate(body().contains(<span
class="code-quote">"A+B+C"</span>))
        .to(<span class="code-quote">"mock:aggregated"</span>);
</pre>
</div></div>

<p>And the same example using Spring XML:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-xml"><span class="code-tag">&lt;camelContext xmlns=<span
class="code-quote">"http://camel.apache.org/schema/spring"</span>&gt;</span>
    <span class="code-tag">&lt;route&gt;</span>
        <span class="code-tag">&lt;from uri=<span class="code-quote">"direct:start"</span>/&gt;</span>
        <span class="code-tag">&lt;aggregate strategyRef=<span class="code-quote">"aggregatorStrategy"</span>&gt;</span>
            <span class="code-tag">&lt;correlationExpression&gt;</span>
                <span class="code-tag">&lt;simple&gt;</span>header.id<span
class="code-tag">&lt;/simple&gt;</span>
            <span class="code-tag">&lt;/correlationExpression&gt;</span>
            <span class="code-tag">&lt;completionPredicate&gt;</span>
                <span class="code-tag">&lt;simple&gt;</span>${body} contains
'A+B+C'<span class="code-tag">&lt;/simple&gt;</span>
            <span class="code-tag">&lt;/completionPredicate&gt;</span>
            <span class="code-tag">&lt;to uri=<span class="code-quote">"mock:aggregated"</span>/&gt;</span>
        <span class="code-tag">&lt;/aggregate&gt;</span>
    <span class="code-tag">&lt;/route&gt;</span>
<span class="code-tag">&lt;/camelContext&gt;</span>

<span class="code-tag">&lt;bean id=<span class="code-quote">"aggregatorStrategy"</span>
class=<span class="code-quote">"org.apache.camel.processor.BodyInAggregatingStrategy"</span>/&gt;</span>
</pre>
</div></div>

<p>And the other situation where we use the <tt>eagerCheckCompletion</tt>
option to tell Camel to use the incoming Exchange. Notice how we can just test in the completion
predicate that the incoming message is the <em>END</em> message:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">from(<span class="code-quote">"direct:start"</span>)
    <span class="code-comment">// aggregate all exchanges correlated by the id header.
</span>    <span class="code-comment">// Aggregate them using the BodyInAggregatingStrategy
strategy
</span>    <span class="code-comment">// <span class="code-keyword">do</span>
eager checking which means the completion predicate will use the incoming exchange
</span>    <span class="code-comment">// which allows us to trigger completion
when a certain exchange arrived which is the
</span>    <span class="code-comment">// END message
</span>    .aggregate(header(<span class="code-quote">"id"</span>), <span
class="code-keyword">new</span> BodyInAggregatingStrategy())
        .eagerCheckCompletion().completionPredicate(body().isEqualTo(<span class="code-quote">"END"</span>))
        .to(<span class="code-quote">"mock:aggregated"</span>);
</pre>
</div></div>

<p>And the same example using Spring XML:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-xml"><span class="code-tag">&lt;camelContext xmlns=<span
class="code-quote">"http://camel.apache.org/schema/spring"</span>&gt;</span>
    <span class="code-tag">&lt;route&gt;</span>
        <span class="code-tag">&lt;from uri=<span class="code-quote">"direct:start"</span>/&gt;</span>
        <span class="code-tag">&lt;aggregate strategyRef=<span class="code-quote">"aggregatorStrategy"</span>
eagerCheckCompletion=<span class="code-quote">"true"</span>&gt;</span>
            <span class="code-tag">&lt;correlationExpression&gt;</span>
                <span class="code-tag">&lt;simple&gt;</span>header.id<span
class="code-tag">&lt;/simple&gt;</span>
            <span class="code-tag">&lt;/correlationExpression&gt;</span>
            <span class="code-tag">&lt;completionPredicate&gt;</span>
                <span class="code-tag">&lt;simple&gt;</span>${body} ==
'END'<span class="code-tag">&lt;/simple&gt;</span>
            <span class="code-tag">&lt;/completionPredicate&gt;</span>
            <span class="code-tag">&lt;to uri=<span class="code-quote">"mock:aggregated"</span>/&gt;</span>
        <span class="code-tag">&lt;/aggregate&gt;</span>
    <span class="code-tag">&lt;/route&gt;</span>
<span class="code-tag">&lt;/camelContext&gt;</span>

<span class="code-tag">&lt;bean id=<span class="code-quote">"aggregatorStrategy"</span>
class=<span class="code-quote">"org.apache.camel.processor.BodyInAggregatingStrategy"</span>/&gt;</span>
</pre>
</div></div>

<h4><a name="Aggregator2-UsingdynamiccompletionTimeout"></a>Using dynamic
completionTimeout</h4>
<p>In this example we want to aggregate all incoming messages and after a period of
inactivity we want the aggregation to complete. The period should be computed at runtime based
on the <tt>timeout</tt> header in the incoming messages. This is done using the
<tt>completionTimeout</tt> option as shown:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">from(<span class="code-quote">"direct:start"</span>)
    <span class="code-comment">// aggregate all exchanges correlated by the id header.
</span>    <span class="code-comment">// Aggregate them using the BodyInAggregatingStrategy
strategy which
</span>    <span class="code-comment">// and the timeout header contains the timeout
in millis of inactivity them timeout and complete the aggregation
</span>    <span class="code-comment">// and send it to mock:aggregated
</span>    .aggregate(header(<span class="code-quote">"id"</span>), <span
class="code-keyword">new</span> BodyInAggregatingStrategy()).completionTimeout(header(<span
class="code-quote">"timeout"</span>))
        .to(<span class="code-quote">"mock:aggregated"</span>);
</pre>
</div></div>

<p>And the same example using Spring XML:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-xml"><span class="code-tag">&lt;camelContext xmlns=<span
class="code-quote">"http://camel.apache.org/schema/spring"</span>&gt;</span>
    <span class="code-tag">&lt;route&gt;</span>
        <span class="code-tag">&lt;from uri=<span class="code-quote">"direct:start"</span>/&gt;</span>
        <span class="code-tag">&lt;aggregate strategyRef=<span class="code-quote">"aggregatorStrategy"</span>&gt;</span>
            <span class="code-tag">&lt;correlationExpression&gt;</span>
                <span class="code-tag">&lt;simple&gt;</span>header.id<span
class="code-tag">&lt;/simple&gt;</span>
            <span class="code-tag">&lt;/correlationExpression&gt;</span>
            <span class="code-tag">&lt;completionTimeout&gt;</span>
                <span class="code-tag">&lt;header&gt;</span>timeout<span
class="code-tag">&lt;/header&gt;</span>
            <span class="code-tag">&lt;/completionTimeout&gt;</span>
            <span class="code-tag">&lt;to uri=<span class="code-quote">"mock:aggregated"</span>/&gt;</span>
        <span class="code-tag">&lt;/aggregate&gt;</span>
    <span class="code-tag">&lt;/route&gt;</span>
<span class="code-tag">&lt;/camelContext&gt;</span>

<span class="code-tag">&lt;bean id=<span class="code-quote">"aggregatorStrategy"</span>
class=<span class="code-quote">"org.apache.camel.processor.BodyInAggregatingStrategy"</span>/&gt;</span>
</pre>
</div></div>

<p><b>Note:</b> You can also add a fixed timeout value and Camel will fallback
to use this value if the dynamic value was <tt>null</tt> or <tt>0</tt>.</p>

<h4><a name="Aggregator2-UsingdynamiccompletionSize"></a>Using dynamic completionSize</h4>
<p>In this example we want to aggregate all incoming messages based on a dynamic size
per correlation key. The size is computed at runtime based on the <tt>mySize</tt>
header in the incoming messages. This is done using the <tt>completionSize</tt>
option as shown:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-java">from(<span class="code-quote">"direct:start"</span>)
    <span class="code-comment">// aggregate all exchanges correlated by the id header.
</span>    <span class="code-comment">// Aggregate them using the BodyInAggregatingStrategy
strategy which
</span>    <span class="code-comment">// and the header mySize determines the
number of aggregated messages should trigger the completion
</span>    <span class="code-comment">// and send it to mock:aggregated
</span>    .aggregate(header(<span class="code-quote">"id"</span>), <span
class="code-keyword">new</span> BodyInAggregatingStrategy()).completionSize(header(<span
class="code-quote">"mySize"</span>))
        .to(<span class="code-quote">"mock:aggregated"</span>);
</pre>
</div></div>

<p>And the same example using Spring XML:</p>
<div class="code panel" style="border-width: 1px;"><div class="codeContent panelContent">
<pre class="code-xml"><span class="code-tag">&lt;camelContext xmlns=<span
class="code-quote">"http://camel.apache.org/schema/spring"</span>&gt;</span>
    <span class="code-tag">&lt;route&gt;</span>
        <span class="code-tag">&lt;from uri=<span class="code-quote">"direct:start"</span>/&gt;</span>
        <span class="code-tag">&lt;aggregate strategyRef=<span class="code-quote">"aggregatorStrategy"</span>&gt;</span>
            <span class="code-tag">&lt;correlationExpression&gt;</span>
                <span class="code-tag">&lt;simple&gt;</span>header.id<span
class="code-tag">&lt;/simple&gt;</span>
            <span class="code-tag">&lt;/correlationExpression&gt;</span>
            <span class="code-tag">&lt;completionSize&gt;</span>
                <span class="code-tag">&lt;header&gt;</span>mySize<span
class="code-tag">&lt;/header&gt;</span>
            <span class="code-tag">&lt;/completionSize&gt;</span>
            <span class="code-tag">&lt;to uri=<span class="code-quote">"mock:aggregated"</span>/&gt;</span>
        <span class="code-tag">&lt;/aggregate&gt;</span>
    <span class="code-tag">&lt;/route&gt;</span>
<span class="code-tag">&lt;/camelContext&gt;</span>

<span class="code-tag">&lt;bean id=<span class="code-quote">"aggregatorStrategy"</span>
class=<span class="code-quote">"org.apache.camel.processor.BodyInAggregatingStrategy"</span>/&gt;</span>
</pre>
</div></div>

<p><b>Note:</b> You can also add a fixed size value and Camel will fallback
to use this value if the dynamic value was <tt>null</tt> or <tt>0</tt>.</p>

<h4><a name="Aggregator2-UsingThisPattern"></a>Using This Pattern</h4>

<p>If you would like to use this EIP Pattern then please read the <a href="/confluence/display/CAMEL/Getting+Started"
title="Getting Started">Getting Started</a>, you may also find the <a href="/confluence/display/CAMEL/Architecture"
title="Architecture">Architecture</a> useful particularly the description of <a
href="/confluence/display/CAMEL/Endpoint" title="Endpoint">Endpoint</a> and <a
href="/confluence/display/CAMEL/URIs" title="URIs">URIs</a>. Then you could try out
some of the <a href="/confluence/display/CAMEL/Examples" title="Examples">Examples</a>
first before trying this pattern out.</p>

<h4><a name="Aggregator2-ManuallyForcetheCompletionofAllAggregatedExchangesImmediately"></a>Manually
Force the Completion of All Aggregated Exchanges Immediately</h4>

<p><b>Available as of Camel 2.9</b><br/>
You can manually complete all current aggregated exchanges by sending in a message containing
the header Exchange.AGGREGATION_COMPLETE_ALL_GROUPS set to true.  The message is considered
a signal message only, the message headers/contents will not be processed otherwise.</p>

<h3><a name="Aggregator2-Seealso"></a>See also</h3>
<ul class="alternate" type="square">
	<li>The <a href="/confluence/display/CAMEL/Loan+Broker+Example" title="Loan Broker
Example">Loan Broker Example</a> which uses an aggregator</li>
	<li><a href="http://tmielke.blogspot.com/2009/01/using-camel-aggregator-correctly.html"
class="external-link" rel="nofollow">Blog post by Torsten Mielke</a> about using
the aggregator correctly.</li>
	<li>The old <a href="/confluence/display/CAMEL/Aggregator" title="Aggregator">Aggregator</a></li>
	<li><a href="/confluence/display/CAMEL/HawtDB" title="HawtDB">HawtDB</a>
or <a href="/confluence/display/CAMEL/SQL+Component" title="SQL Component">SQL Component</a>
for persistence support</li>
	<li><a href="/confluence/display/CAMEL/Aggregate+Example" title="Aggregate Example">Aggregate
Example</a> for an example application</li>
</ul>

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