Modified: websites/production/camel/content/aggregator2.html
==============================================================================
--- websites/production/camel/content/aggregator2.html (original)
+++ websites/production/camel/content/aggregator2.html Thu Aug 31 23:20:55 2017
@@ -75,190 +75,8 @@
<tbody>
<tr>
<td valign="top" width="100%">
-<div class="wiki-content maincontent"><h3
id="Aggregator2-Aggregator">Aggregator</h3><p><strong>This applies for Camel
version 2.3 or newer. If you use an older version then use this <a shape="rect"
href="aggregator.html">Aggregator</a> link instead.</strong></p><p>The <a
shape="rect" class="external-link"
href="http://www.enterpriseintegrationpatterns.com/Aggregator.html";
rel="nofollow">Aggregator</a> from the <a shape="rect"
href="enterprise-integration-patterns.html">EIP patterns</a> allows you to
combine a number of messages together into a single message.</p><p><span
class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image
confluence-external-resource"
src="http://www.enterpriseintegrationpatterns.com/img/Aggregator.gif";
data-image-src="http://www.enterpriseintegrationpatterns.com/img/Aggregator.gif";></span></p><p>A
correlation <a shape="rect" href="expression.html">Expression</a> is used to
determine the messages which should be aggregated together. If yo
u 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
id="Aggregator2-Aggregatoroptions">Aggregator options</h3><p>The aggregator
supports the following options:</p><parameter
ac:name="class">confluenceTableSmall</parameter><rich-text-body><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>Option</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Default</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p>correlationExpression</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Mandatory <a shape="rect"
href="expression.html">Expression</a> which evaluates the correlation key to u
se for aggregation. The <a shape="rect" href="exchange.html">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 <code>ignoreBadCorrelationKeys</code> option.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p>aggregationStrategy</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Mandatory <code>AggregationStrategy</code>
which is used to <em>merge</em> the incoming <a shape="rect"
href="exchange.html">Exchange</a> with the existing already merged exchanges.
At first call the <code>oldExchange</code> parameter is <code>null</code>. On
subsequent invocations the <code>oldExchange</code> contains the merged
exchanges and <code>newExchange</code> is of course the new incoming Exchange.
From <strong>Camel 2.9.2</strong> onwards the strategy can also be a
<code>TimeoutAware
AggregationStrategy</code> implementation, supporting the timeout callback,
see further below for more details. From <strong>Camel 2.16</strong> onwards
the strategy can also be a <code>PreCompletionAwareAggregationStrategy</code>
implementation which then runs the completion check in pre-completion mode. See
further below for more details.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>strategyRef</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>A reference to lookup the
<code>AggregationStrategy</code> in the <a shape="rect"
href="registry.html">Registry</a>. From <strong>Camel 2.12</strong> onwards you
can also use a POJO as the <code>AggregationStrategy</code>, see further below
for details.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>strategyMethodName</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1" c
lass="confluenceTd"><p><strong>Camel 2.12:</strong> This option can be used to
explicit declare the method name to use, when using POJOs as the
<code>AggregationStrategy</code>. See further below for more
details.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>strategyMethodAllowNull</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong> If this option
is <code>false</code> then the aggregate method is not used for the very first
aggregation. If this option is <code>true</code> then <code>null</code> values
is used as the <code>oldExchange</code> (at the very first aggregation), when
using POJOs as the <code>AggregationStrategy</code>. See further below for more
details.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>completionSize</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p> </p></td><td colspan="1" rowspan
="1" class="confluenceTd"><p>Number of messages aggregated before the
aggregation is complete. This option can be set as either a fixed value or
using an <a shape="rect" href="expression.html">Expression</a> which allows you
to evaluate a size dynamically - will use <code>Integer</code> as result. If
both are set Camel will fallback to use the fixed value if the <a shape="rect"
href="expression.html">Expression</a> result was <code>null</code> or
<code>0</code>.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>completionTimeout</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>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 shape="rect" href="expression.html">Expression</a> which allows you
to evaluate a timeout dynamically - will use <code>Long</code> as result. If
both are set Camel will fa
llback to use the fixed value if the <a shape="rect"
href="expression.html">Expression</a> result was <code>null</code> or
<code>0</code>. You cannot use this option together with completionInterval,
only one of the two can be used.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>completionInterval</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>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.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p>completionPredicate</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>A <a shape="rect"
href="predicate.html">Predicate</a> to indicate when an aggrega
ted exchange is complete. Starting in <strong>Camel 2.15</strong>, if this is
not specified and the AggregationStrategy object implements Predicate, the
aggregationStrategy object will be used as the
completionPredicate.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>completionFromBatchConsumer</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>This option is if the exchanges are coming
from a <a shape="rect" href="batch-consumer.html">Batch Consumer</a>. Then when
enabled the <a shape="rect" href="aggregator2.html">Aggregator2</a> will use
the batch size determined by the <a shape="rect"
href="batch-consumer.html">Batch Consumer</a> in the message header
<code>CamelBatchSize</code>. See more details at <a shape="rect"
href="batch-consumer.html">Batch Consumer</a>. This can be used to aggregate
all files consumed from a <a shape="rect" href="file2.html">File</a> endpoint
in
that given poll.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>forceCompletionOnStop</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.9</strong> Indicates to
complete all current aggregated exchanges when the context is
stopped</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd">completeAllOnStop</td><td colspan="1" rowspan="1"
class="confluenceTd"><code>false</code></td><td colspan="1" rowspan="1"
class="confluenceTd"><strong>Camel 2.16:</strong> Indicates to wait to
complete all current and partial (pending) aggregated exchanges when the
context is stopped. This also means that we will wait for all pending exchanges
which are stored in the aggregation repository to complete so the
repository is empty before we can stop.  You may want to enable this when
using the memory based aggregation repository that is memory based o
nly, and do not store data on disk. When this option is enabled, then the
aggregator is waiting to complete all those exchanges before its stopped,
when stopping CamelContext or the route using it.</td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p>eagerCheckCompletion</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Whether or not to eager check
for completion when a new incoming <a shape="rect"
href="exchange.html">Exchange</a> has been received. This option influences the
behavior of the <code>completionPredicate</code> option as the <a shape="rect"
href="exchange.html">Exchange</a> being passed in changes accordingly. When
<code>false</code> the <a shape="rect" href="exchange.html">Exchange</a> passed
in the <a shape="rect" href="predicate.html">Predicate</a> is the
<em>aggregated</em> Exchange which means any information you may store on the
aggregated Exchange from
the <code>AggregationStrategy</code> is available for the <a shape="rect"
href="predicate.html">Predicate</a>. When <code>true</code> the <a shape="rect"
href="exchange.html">Exchange</a> passed in the <a shape="rect"
href="predicate.html">Predicate</a> is the <em>incoming</em> <a shape="rect"
href="exchange.html">Exchange</a>, which means you can access data from the
incoming Exchange.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>groupExchanges</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>If enabled then Camel will group all aggregated
Exchanges into a single combined
<code>org.apache.camel.impl.GroupedExchange</code> 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 <code>AggregationStrate
gy</code> yourself. <strong>Important:</strong> This option does
<strong>not</strong> support persistent repository with the aggregator. See
further below for an example and more details.</p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p>ignoreInvalidCorrelationKeys</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>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.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>closeCorrelationKeyOnCompletion</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>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 <code>closedCorrelationKeyException</code> exception. When using
this option you pass in a <code>integer</code> 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.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>discardOnCompletionTimeout</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.5:</strong> Whether or not
exchanges which complete due to a timeout should be discarded. If enabled then
when a timeout occurs the aggregated message will <strong>not</strong> be sent
out but dropped (discarded).</p></td></tr><tr><td colspan="1" rowspan="1"
class="
confluenceTd"><p>aggregationRepository</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>Allows you to plugin you own implementation of
<code>org.apache.camel.spi.AggregationRepository</code> which keeps track of
the current inflight aggregated exchanges. Camel uses by default a memory based
implementation.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>aggregationRepositoryRef</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>Reference to lookup a
<code>aggregationRepository</code> in the <a shape="rect"
href="registry.html">Registry</a>.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>parallelProcessing</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>When aggregated are completed they are being sen
d 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.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>executorService</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>If using <code>parallelProcessing</code> you can
specify a custom thread pool to be used. In fact also if you are not using
<code>parallelProcessing</code> this custom thread pool is used to send out
aggregated exchanges as well.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>executorServiceRef</p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>Reference to lookup a <code>executorService</code> in
the <a shape="rect" href="registry.html">Registr
y</a></p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>timeoutCheckerExecutorService</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><strong>Camel 2.9:</strong> If using either of the
<code>completionTimeout</code>, <code>completionTimeoutExpression</code>, or
<code>completionInterval</code> 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.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>timeoutCheckerExecutorServiceRef</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.9:</strong> Reference to
lookup a <code>timeoutCheckerExecutorService</code> in the <a shape="rect"
href="registry.html">Registry</a></p></td></tr><tr><td c
olspan="1" rowspan="1" class="confluenceTd"><p>optimisticLocking</p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.11:</strong>
Turns on using optimistic locking, which requires the
<code>aggregationRepository</code> being used, is supporting this by
implementing the
<code>org.apache.camel.spi.OptimisticLockingAggregationRepository</code>
interface.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p>optimisticLockRetryPolicy</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><strong>Camel 2.11.1:</strong> Allows to configure
retry settings when using optimistic
locking.</p></td></tr></tbody></table></div></rich-text-body><h3
id="Aggregator2-ExchangeProperties">Exchange Properties</h3><p>The following
properties are set on each aggregated Exchange:</p><parameter
ac:name="class">confluence
TableSmall</parameter><rich-text-body><div class="table-wrap"><table
class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1"
class="confluenceTh"><p>header</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>type</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>description</p></th></tr><tr><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>CamelAggregatedSize</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>int</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>The total number of Exchanges aggregated
into this combined Exchange.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>CamelAggregatedCompletedBy</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>String</p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Indicator how the aggregation was completed
as a value of either: <code>predicate</code>, <code>size</code>,
<code>strategy</code>, <code>consumer</code>, <code>time
out</code>, <code>forceCompletion</code> or
<code>interval</code>.</p></td></tr></tbody></table></div></rich-text-body><h3
id="Aggregator2-AboutAggregationStrategy">About AggregationStrategy</h3><p>The
<code>AggregationStrategy</code> 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><plain-text-body>//simply combines Exchange String body values
using '+' as a delimiter
-class StringAggregationStrategy implements AggregationStrategy {
-
- public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
- if (oldExchange == null) {
- return newExchange;
- }
-
- String oldBody = oldExchange.getIn().getBody(String.class);
- String newBody = newExchange.getIn().getBody(String.class);
- oldExchange.getIn().setBody(oldBody + "+" + newBody);
- return oldExchange;
- }
-}
-
-//simply combines Exchange body values into an ArrayList<Object>
-class ArrayListAggregationStrategy implements AggregationStrategy {
-
- public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
- Object newBody = newExchange.getIn().getBody();
- ArrayList<Object> list = null;
- if (oldExchange == null) {
- list = new ArrayList<Object>();
- list.add(newBody);
- newExchange.getIn().setBody(list);
- return newExchange;
- } else {
- list = oldExchange.getIn().getBody(ArrayList.class);
- list.add(newBody);
- return oldExchange;
- }
- }
-}
-</plain-text-body><h3 id="Aggregator2-Aboutcompletion">About
completion</h3><p>When aggregation <a shape="rect"
href="exchange.html">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"><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
shape="rect" href="predicate.html">Predicate</a> when a new exchange is
aggregated to determine if we are complete or not. Staring
in <strong>Camel 2.15</strong>, the configured aggregationStrategy can
implement the Predicate
interface and will be used as the completionPredicate if no
completionPredicate is configured. From <strong>Camel 2.16</strong>, the
configured aggregationStrategy can
implement <code>PreCompletionAwareAggregationStrategy</code> and will be
used as the completionPredicate in pre-complete check mode. See further below
for more details.</li><li>completionFromBatchConsumer - Special option for <a
shape="rect" href="batch-consumer.html">Batch Consumer</a> which allows you to
complete when all the messages from the batch has been
aggregated.</li><li>forceCompletionOnStop - <strong>Camel 2.9</strong>
Indicates to complete all current aggregated exchanges when the context is
stopped</li><li>Using a <code>AggregateController</code>
- <strong>Camel 2.16</strong> which allows to use an external source to
complete groups or all groups. This can be done using Java or JMX
API.</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><parameter
ac:name="title">Callbacks</parameter><rich-text-body><p>See the
<code>TimeoutAwareAggregationStrategy</code> and
<code>CompletionAwareAggregationStrategy</code> extensions to
<code>AggregationStrategy</code> that has callbacks when the aggregated
Exchange was completed and if a timeout occurred.</p></rich-text-body><h3
id="Aggregator2-Pre-completionmode">Pre-completion
mode</h3><p><strong>available as of Camel 2.16</strong></p><p>There can be
use-cases where you want the incoming <a shape="rect"
href="exchange.html">Exchange</a> to determine if the correlation group
should pre-complete, and then the inco
ming <a shape="rect" href="exchange.html">Exchange</a> is starting a new
group from scratch. To determine this the <code>AggregationStrategy</code>
can implement <code>PreCompletionAwareAggregationStrategy</code> which has
a <code>preComplete</code> method:</p><plain-text-body> /**
- * Determines if the aggregation should complete the current group, and
start a new group, or the aggregation
- * should continue using the current group.
- *
- * @param oldExchange the oldest exchange (is <tt>null</tt> on
first aggregation as we only have the new exchange)
- * @param newExchange the newest exchange (can be
<tt>null</tt> if there was no data possible to acquire)
- * @return <tt>true</tt> to complete current group and start a
new group, or <tt>false</tt> to keep using current
- */
- boolean preComplete(Exchange oldExchange, Exchange
newExchange);</plain-text-body><p>If the preComplete method returns true, then
the existing groups is completed (without aggregating the incoming exchange
(newExchange). And then the newExchange is used to start the correlation group
from scratch so the group would contain only that new incoming exchange. This
is known as pre-completion mode. And when the aggregation is in pre-completion
mode, then only the following completions are in use</p><ul
style="list-style-type: square;"><li>aggregationStrategy must
implement <code>PreCompletionAwareAggregationStrategy</code> xxx</li><li>completionTimeout
or completionInterval can also be used as fallback completions</li><li>any
other completion are not used (such as by size, from batch consumer
etc)</li><li>eagerCheckCompletion is implied as true, but the option has no
effect</li></ul><h3 id="Aggregator2-PersistentAggregationRepository">Persistent
AggregationRepository</h3><p>
The aggregator provides a pluggable repository which you can implement your
own <code>org.apache.camel.spi.AggregationRepository</code>.<br clear="none">
If you need persistent repository then you can use either Camel <a shape="rect"
href="hawtdb.html">HawtDB</a>, <a shape="rect" href="leveldb.html">LevelDB</a>,
or <a shape="rect" href="sql-component.html">SQL Component</a>
components.</p><h3 id="Aggregator2-Examples">Examples</h3><p>See some examples
from the old <a shape="rect" href="aggregator.html">Aggregator</a> which is
somewhat similar to this new aggregator.</p><parameter ac:name="title">Setting
options in Spring XML</parameter><rich-text-body><p>Many of the options are
configurable as attributes on the <code><aggregate></code> tag when using
Spring XML.</p></rich-text-body><h4
id="Aggregator2-UsingcompletionTimeout">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 com
plete. This is done using the <code>completionTimeout</code> option as
shown:<plain-text-body>{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/aggregator/AggregateSimpleTimeoutTest.java}</plain-text-body>And
the same example using Spring
XML:<plain-text-body>{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/aggregator/SpringAggregateSimpleTimeoutTest.xml}</plain-text-body></p><h4
id="Aggregator2-UsingTimeoutAwareAggregationStrategy">Using
TimeoutAwareAggregationStrategy</h4><p><strong>Available as of Camel
2.9.2</strong></p><p>If your aggregation strategy implements
<code>TimeoutAwareAggregationStrategy</code>, then Camel will invoke the
<code>timeout</code> method when the timeout occurs. Notice that the values for
index and total parameters will be -1, and the timeout parameter will be
provided only if configured as a fixed value. You must <strong>not</strong>
throw any e
xceptions from the <code>timeout</code> method.</p><h4
id="Aggregator2-UsingCompletionAwareAggregationStrategy">Using
CompletionAwareAggregationStrategy</h4><p><strong>Available as of Camel
2.9.3</strong></p><p>If your aggregation strategy implements
<code>CompletionAwareAggregationStrategy</code>, then Camel will invoke the
<code>onComplete</code> method when the aggregated Exchange is completed. This
allows you to do any last minute custom logic such as to cleanup some
resources, or additional work on the exchange as it's now completed.<br
clear="none"> You must <strong>not</strong> throw any exceptions from the
<code>onCompletion</code> method.</p><h4
id="Aggregator2-UsingcompletionSize">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 <code>completionSize</code> option as
shown:<plain-text-body>{snippet:id=e1|lan
g=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/aggregator/AggregateSimpleSizeTest.java}</plain-text-body>And
the same example using Spring
XML:<plain-text-body>{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/aggregator/SpringAggregateSimpleSizeTest.xml}</plain-text-body></p><h4
id="Aggregator2-UsingcompletionPredicate">Using completionPredicate</h4><p>In
this example we want to aggregate all incoming messages and use a <a
shape="rect" href="predicate.html">Predicate</a> to determine when we are
complete. The <a shape="rect" href="predicate.html">Predicate</a> can be
evaluated using either the aggregated exchange (default) or the incoming
exchange. We will give an example for both situations. We start with the
default situation as
shown:<plain-text-body>{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/aggregator/AggregateSimplePredicateTest.java
}</plain-text-body>And the same example using Spring
XML:<plain-text-body>{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/aggregator/SpringAggregateSimplePredicateTest.xml}</plain-text-body>And
the other situation where we use the <code>eagerCheckCompletion</code> 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:<plain-text-body>{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/aggregator/AggregateSimplePredicateEagerTest.java}</plain-text-body>And
the same example using Spring
XML:<plain-text-body>{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/aggregator/SpringAggregateSimplePredicateEagerTest.xml}</plain-text-body></p><h4
id="Aggregator2-UsingdynamiccompletionTimeout">Using dynamic completion
Timeout</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 <code>timeout</code> header in the
incoming messages. This is done using the <code>completionTimeout</code> option
as
shown:<plain-text-body>{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/aggregator/AggregateExpressionTimeoutTest.java}</plain-text-body>And
the same example using Spring
XML:<plain-text-body>{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/aggregator/SpringAggregateExpressionTimeoutTest.xml}</plain-text-body><strong>Note:</strong>
You can also add a fixed timeout value and Camel will fallback to use this
value if the dynamic value was <code>null</code> or <code>0</code>.</p><h4
id="Aggregator2-UsingdynamiccompletionSize">Using dynamic
completionSize</h4><p>In th
is 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
<code>mySize</code> header in the incoming messages. This is done using the
<code>completionSize</code> option as
shown:<plain-text-body>{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/aggregator/AggregateExpressionSizeTest.java}</plain-text-body>And
the same example using Spring
XML:<plain-text-body>{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/aggregator/SpringAggregateExpressionSizeTest.xml}</plain-text-body><strong>Note:</strong>
You can also add a fixed size value and Camel will fallback to use this value
if the dynamic value was <code>null</code> or <code>0</code>.</p><p><parameter
ac:name=""><a shape="rect" href="using-this-pattern.html">Using This
Pattern</a></parameter></p><h4 id="Aggregator2-Completingcurrentgroupdeci
dedfromtheAggregationStrategy">Completing current group decided from the
AggregationStrategy</h4><p><strong>Available as of Camel
2.15</strong></p><p>The <code>AggregationStrategy</code> can now included
a property on the returned <code>Exchange</code> that contains a boolean
to indicate if the current group should be completed. This allows to overrule
any existing completion predicates / sizes / timeouts etc, and complete the
group.</p><p>For example the following logic (from an unit test) will complete
the group if the message body size is larger than 5. This is done by setting
the property <span style="line-height:
1.4285715;">Exchange.AGGREGATION_COMPLETE_CURRENT_GROUP to
true.</span></p><plain-text-body> public final class MyCompletionStrategy
implements AggregationStrategy {
- @Override
- public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
- if (oldExchange == null) {
- return newExchange;
- }
- String body = oldExchange.getIn().getBody(String.class) + "+"
- + newExchange.getIn().getBody(String.class);
- oldExchange.getIn().setBody(body);
- if (body.length() >= 5) {
-
oldExchange.setProperty(Exchange.AGGREGATION_COMPLETE_CURRENT_GROUP, true);
- }
- return oldExchange;
- }
- }</plain-text-body><p> </p><h4
id="Aggregator2-ManuallyForcetheCompletionofAllAggregatedExchangesImmediately">Manually
Force the Completion of All Aggregated Exchanges
Immediately</h4><p><strong>Available as of Camel 2.9</strong><br clear="none">
You can manually trigger completion of all current aggregated exchanges by
sending 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><p><strong>Available as of Camel 2.11</strong><br clear="none">
You can alternatively set the header
Exchange.AGGREGATION_COMPLETE_ALL_GROUPS_INCLUSIVE to true to trigger
completion of all groups after processing the current message.</p><h4
id="Aggregator2-UsingaList<V>inAggregationStrategy">Using a List<V>
in AggregationStrategy</h4><p><strong>Available as of Camel
2.11</strong></p><p>If you want to aggregate some value from the messages <
;V> into a List<V> then we have added a
<code>org.apache.camel.processor.aggregate.AbstractListAggregationStrategy</code>
abstract class in <strong>Camel 2.11</strong> that makes this easier. The
completed Exchange that is sent out of the aggregator will contain the
List<V> in the message body.</p><p>For example to aggregate a
List<Integer> you can extend this class as shown below, and implement the
<code>getValue</code>
method:<plain-text-body>{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/aggregator/CustomListAggregationStrategyTest.java}</plain-text-body></p><h3
id="Aggregator2-UsingAggregateController">Using
AggregateController</h3><p><strong>Available as of Camel
2.16</strong></p><p>The <code>org.apache.camel.processor.aggregate.AggregateController</code>
allows you to control the aggregate at runtime using Java or JMX API. This can
be used to force completing groups of exchanges, or query its current runti
me statistics.</p><p>The aggregator provides a default implementation if no
custom have been configured, which can be accessed
using <code>getAggregateController()</code> method. Though it may be
easier to configure a controller in the route using aggregateController as
shown below:</p><plain-text-body>private AggregateController controller = new
DefaultAggregateController();
- 
-from("direct:start")
- .aggregate(header("id"), new
MyAggregationStrategy()).completionSize(10).id("myAggregator")
- .aggregateController(controller)
- .to("mock:aggregated");</plain-text-body><p>Then there is API on
AggregateController to force completion. For example to complete a group with
key foo</p><plain-text-body>int groups =
controller.forceCompletionOfGroup("foo");</plain-text-body><p>The number return
would be the number of groups completed. In this case it would be 1 if the foo
group existed and was completed. If foo does not exists then 0 is
returned.</p><p>There is also an api to complete all
groups</p><plain-text-body>int groups =
controller.forceCompletionOfAllGroups();</plain-text-body><p> </p><p>To
configure this from XML DSL</p><plain-text-body><bean id="myController"
class="org.apache.camel.processor.aggregate.DefaultAggregateController"/>
- 
- <camelContext xmlns="http://camel.apache.org/schema/spring">
- <route>
- <from uri="direct:start"/>
- <aggregate strategyRef="myAppender" completionSize="10"
aggregateControllerRef="myController">
- <correlationExpression>
- <header>id</header>
- </correlationExpression>
- <to uri="mock:result"/>
- </aggregate>
- </route>
- </camelContext></plain-text-body><p> </p><p>There is also JMX
API on the aggregator which is available under the processors node in the Camel
JMX tree.</p><p> </p><h3 id="Aggregator2-UsingGroupedExchanges">Using
GroupedExchanges</h3><p>In the route below we group all the exchanges together
using <code>groupExchanges()</code>:</p><plain-text-body>
from("direct:start")
- // aggregate all using same expression
- .aggregate(constant(true))
- // wait for 0.5 seconds to aggregate
- .completionTimeout(500L)
- // group the exchanges so we get one single exchange
containing all the others
- .groupExchanges()
- .to("mock:result");
-</plain-text-body><p>As a result we have one outgoing <a shape="rect"
href="exchange.html">Exchange</a> being routed the the "mock:result" endpoint.
The exchange is a holder containing all the incoming Exchanges.<br
clear="none"> To get access to these exchanges you need to access them from a
property on the outgoing exchange as
shown:</p><plain-text-body>List<Exchange> grouped =
out.getProperty(Exchange.GROUPED_EXCHANGE, List.class);
-</plain-text-body><p>From <strong>Camel 2.13</strong> onwards this behavior
has changed to store these exchanges directly on the message body which is more
intuitive:</p><plain-text-body>List<Exchange> grouped =
exchange.getIn().getBody(List.class);
-</plain-text-body><rich-text-body><p>Notice the old way using the property is
still present in <strong>Camel 2.13</strong> onwards, but its considered
deprecated and to be removed in Camel 3.0 onwards.</p></rich-text-body><h3
id="Aggregator2-UsingPOJOsasAggregationStrategy">Using POJOs as
AggregationStrategy</h3><p><strong>Available as of Camel
2.12</strong></p><rich-text-body><p>You can use POJOs as AggregationStrategy
with the other <a shape="rect" href="eip.html">EIP</a>s that supports
aggregation, such as <a shape="rect" href="splitter.html">Splitter</a>, <a
shape="rect" href="recipient-list.html">Recipient List</a>,
etc.</p></rich-text-body><p>To use the <code>AggregationStrategy</code> you had
to implement the
<code>org.apache.camel.processor.aggregate.AggregationStrategy</code>
interface, which means your logic would be tied to the Camel API. From
<strong>Camel 2.12</strong> onwards you can use a POJO for the logic and let
Camel adapt to your POJO. To use a POJO a convention
must be followed:</p><ul class="alternate"><li>there must be a public method
to use</li><li>the method must not be void</li><li>the method can be static or
non-static</li><li>the method must have 2 or more parameters</li><li>the
parameters is paired so the first 50% is applied to the
<code>oldExchange</code> and the reminder 50% is for the
<code>newExchange</code></li><li>.. meaning that there must be an equal number
of parameters, eg 2, 4, 6 etc.</li></ul><p>The paired methods is expected to be
ordered as follows:</p><ul class="alternate"><li>the first parameter is the
message body</li><li>the 2nd parameter is a Map of the headers</li><li>the 3rd
parameter is a Map of the Exchange properties</li></ul><p>This convention is
best explained with some examples.</p><p>In the method below, we have only 2
parameters, so the 1st parameter is the body of the <code>oldExchange</code>,
and the 2nd is paired to the body of the
<code>newExchange</code>:</p><plain-text-body>public String append(S
tring existing, String next) {
- return existing + next;
-}
-</plain-text-body><p>In the method below, we have only 4 parameters, so the
1st parameter is the body of the <code>oldExchange</code>, and the 2nd is the
Map of the <code>oldExchange} headers, and the 3rd is paired to the body of the
{{newExchange</code>, and the 4th parameter is the Map of the
<code>newExchange</code> headers:</p><plain-text-body>public String
append(String existing, Map existingHeaders, String next, Map nextHeaders) {
- return existing + next;
-}
-</plain-text-body><p>And finally if we have 6 parameters the we also have the
properties of the <a shape="rect"
href="exchange.html">Exchange</a>s:</p><plain-text-body>public String
append(String existing, Map existingHeaders, Map existingProperties, String
next, Map nextHeaders, Map nextProperties) {
- return existing + next;
-}
-</plain-text-body><p>To use this with the <a shape="rect"
href="aggregator2.html">Aggregate</a> EIP we can use a POJO with the aggregate
logic as follows:</p><plain-text-body>public class MyBodyAppender {
-
- public String append(String existing, String next) {
- return next + existing;
- }
-
-}
-</plain-text-body><p>And then in the Camel route we create an instance of our
bean, and then refer to the bean in the route using <code>bean</code> method
from <code>org.apache.camel.util.toolbox.AggregationStrategies</code> as
shown:</p><plain-text-body> private MyBodyAppender appender = new
MyBodyAppender();
-
- public void configure() throws Exception {
- from("direct:start")
- .aggregate(constant(true), AggregationStrategies.bean(appender,
"append"))
- .completionSize(3)
- .to("mock:result");
- }
-</plain-text-body><p>We can also provide the bean type
directly:</p><plain-text-body> public void configure() throws Exception {
- from("direct:start")
- .aggregate(constant(true),
AggregationStrategies.bean(MyBodyAppender.class, "append"))
- .completionSize(3)
- .to("mock:result");
- }
-</plain-text-body><p>And if the bean has only one method we do not need to
specify the name of the method:</p><plain-text-body> public void configure()
throws Exception {
- from("direct:start")
- .aggregate(constant(true),
AggregationStrategies.bean(MyBodyAppender.class))
- .completionSize(3)
- .to("mock:result");
- }
-</plain-text-body><p>And the <code>append</code> method could be
static:</p><plain-text-body>public class MyBodyAppender {
-
- public static String append(String existing, String next) {
- return next + existing;
- }
-
-}
-</plain-text-body><p>If you are using XML DSL then we need to declare a
<bean> with the POJO:</p><parameter
ac:name="">xml</parameter><plain-text-body> <bean id="myAppender"
class="com.foo.MyBodyAppender"/>
-</plain-text-body><p>And in the Camel route we use <code>strategyRef</code> to
refer to the bean by its id, and the <code>strategyMethodName</code> can be
used to define the method name to call:</p><parameter
ac:name="">xml</parameter><plain-text-body> <camelContext
xmlns="http://camel.apache.org/schema/spring">
- <route>
- <from uri="direct:start"/>
- <aggregate strategyRef="myAppender" strategyMethodName="append"
completionSize="3">
- <correlationExpression>
- <constant>true</constant>
- </correlationExpression>
- <to uri="mock:result"/>
- </aggregate>
- </route>
- </camelContext>
-</plain-text-body><p>When using XML DSL you must define the POJO as a
<bean>.</p><h4 id="Aggregator2-Aggregatingwhennodata">Aggregating when no
data</h4><p>By default when using POJOs as AggregationStrategy, then the method
is <strong>only</strong> invoked when there is data to be aggregated (by
default). You can use the option <code>strategyMethodAllowNull</code> to
configure this. Where as without using POJOs then you may have
<code>null</code> as <code>oldExchange</code> or <code>newExchange</code>
parameters. For example the <a shape="rect"
href="aggregator2.html">Aggregate</a> EIP will invoke the
<code>AggregationStrategy</code> with <code>oldExchange</code> as null, for the
first <a shape="rect" href="exchange.html">Exchange</a> incoming to the
aggregator. And then for subsequent <a shape="rect"
href="exchange.html">Exchange</a>s then <code>oldExchange</code> and
<code>newExchange</code> parameters are both not null.</p><h5
id="Aggregator2-Examplewithandnodata">Example w
ith <a shape="rect" href="content-enricher.html">Content Enricher</a> and no
data</h5><p>Though with POJOs as AggregationStrategy we made this simpler and
only call the method when <code>oldExchange</code> and <code>newExchange</code>
is not null, as that would be the most common use-case. If you need to allow
<code>oldExchange</code> or <code>newExchange</code> to be null, then you can
configure this with the POJO using the
<code>AggregationStrategyBeanAdapter</code> as shown below. On the bean adapter
we call <code>setAllowNullNewExchange</code> to allow the new exchange to be
null.</p><plain-text-body> public void configure() throws Exception {
- AggregationStrategyBeanAdapter myStrategy = new
AggregationStrategyBeanAdapter(appender, "append");
- myStrategy.setAllowNullOldExchange(true);
- myStrategy.setAllowNullNewExchange(true);
-
- from("direct:start")
- .pollEnrich("seda:foo", 1000, myStrategy)
- .to("mock:result");
- }
-</plain-text-body><p>This can be configured a bit easier using the
<code>beanAllowNull</code> method from <code>AggregationStrategies</code> as
shown:</p><plain-text-body> public void configure() throws Exception {
- from("direct:start")
- .pollEnrich("seda:foo", 1000,
AggregationStrategies.beanAllowNull(appender, "append"))
- .to("mock:result");
- }
-</plain-text-body><p>Then the <code>append</code> method in the POJO would
need to deal with the situation that <code>newExchange</code> can be
null:</p><plain-text-body> public class MyBodyAppender {
-
- public String append(String existing, String next) {
- if (next == null) {
- return "NewWasNull" + existing;
- } else {
- return existing + next;
- }
- }
-
- }
-</plain-text-body><p>In the example above we use the <a shape="rect"
href="content-enricher.html">Content Enricher</a> EIP using
<code>pollEnrich</code>. The <code>newExchange</code> will be null in the
situation we could not get any data from the "seda:foo" endpoint, and therefore
the timeout was hit after 1 second. So if we need to do some special merge
logic we would need to set <code>setAllowNullNewExchange=true</code>, so the
<code>append</code> method will be invoked. If we do not do that then when the
timeout was hit, then the append method would normally not be invoked, meaning
the <a shape="rect" href="content-enricher.html">Content Enricher</a> did not
merge/change the message.</p><p>In XML DSL you would configure the
<code>strategyMethodAllowNull</code> option and set it to true as shown
below:</p><parameter ac:name="">xml</parameter><plain-text-body>
<camelContext xmlns="http://camel.apache.org/schema/spring">
- <route>
- <from uri="direct:start"/>
- <aggregate strategyRef="myAppender" strategyMethodName="append"
strategyMethodAllowNull="true" completionSize="3">
- <correlationExpression>
- <constant>true</constant>
- </correlationExpression>
- <to uri="mock:result"/>
- </aggregate>
- </route>
- </camelContext>
-</plain-text-body><h5 id="Aggregator2-Differentbodytypes">Different body
types</h5><p>When for example using <code>strategyMethodAllowNull</code> as
true, then the parameter types of the message bodies does not have to be the
same. For example suppose we want to aggregate from a <code>com.foo.User</code>
type to a <code>List<String></code> that contains the user name. We could
code a POJO doing this as follows:</p><plain-text-body> public static final
class MyUserAppender {
-
- public List addUsers(List names, User user) {
- if (names == null) {
- names = new ArrayList();
- }
- names.add(user.getName());
- return names;
- }
- }
-</plain-text-body><p>Notice that the return type is a List which we want to
contain the user names. The 1st parameter is the list of names, and then notice
the 2nd parameter is the incoming <code>com.foo.User</code> type.</p><h3
id="Aggregator2-Seealso">See also</h3><ul class="alternate"><li>The <a
shape="rect" href="loan-broker-example.html">Loan Broker Example</a> which uses
an aggregator</li><li><a shape="rect" class="external-link"
href="http://tmielke.blogspot.com/2009/01/using-camel-aggregator-correctly.html";
rel="nofollow">Blog post by Torsten Mielke</a> about using the aggregator
correctly.</li><li>The old <a shape="rect"
href="aggregator.html">Aggregator</a></li><li><a shape="rect"
href="hawtdb.html">HawtDB</a>, <a shape="rect" href="leveldb.html">LevelDB</a>
or <a shape="rect" href="sql-component.html">SQL Component</a> for persistence
support</li><li><a shape="rect" href="aggregate-example.html">Aggregate
Example</a> for an example application</li></ul></div>
+<div class="wiki-content maincontent"><h3
id="Aggregator2-Aggregator">Aggregator</h3><p><strong>This applies for Camel
version 2.3 or newer. If you use an older version then use this <a shape="rect"
href="aggregator.html">Aggregator</a> link instead.</strong></p><p>The <a
shape="rect" class="external-link"
href="http://www.enterpriseintegrationpatterns.com/Aggregator.html";
rel="nofollow">Aggregator</a> from the <a shape="rect"
href="enterprise-integration-patterns.html">EIP patterns</a> allows you to
combine a number of messages together into a single message.</p><p><span
class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image
confluence-external-resource"
src="http://www.enterpriseintegrationpatterns.com/img/Aggregator.gif";
data-image-src="http://www.enterpriseintegrationpatterns.com/img/Aggregator.gif";></span></p><p>A
correlation <a shape="rect" href="expression.html">Expression</a> is used to
determine the messages which should be aggregated together. If yo
u want to aggregate all messages into a single message, just use a constant
expression. An <strong><code>AggregationStrategy</code></strong> is used
to combine all the message exchanges for a single correlation key into a single
message exchange.</p><h3 id="Aggregator2-Aggregatoroptions">Aggregator
options</h3><p>The aggregator supports the following
options:</p><p>confluenceTableSmall</p><div class="table-wrap"><table
class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1"
class="confluenceTh"><p>Option</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Default</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>correlationExpression</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Mandatory <a shape="rect"
href="expression.html">Expression</a> which evaluates the correlation key to u
se for aggregation. The <a shape="rect" href="exchange.html">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 <strong><code>ignoreBadCorrelationKeys</code></strong>
option.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>aggregationStrategy</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Mandatory
<strong><code>AggregationStrategy</code></strong> which is used to
<em>merge</em> the incoming <a shape="rect" href="exchange.html">Exchange</a>
with the existing already merged exchanges. At first call the
<strong><code>oldExchange</code></strong> parameter is
<strong><code>null</code></strong>. On subsequent invocations the
<strong><code>oldExchange</code></strong> contains the merged exchanges and
<strong><code>newExchange</code></strong> is of course
the new incoming Exchange.</p><p>From <strong>Camel 2.9.2</strong> onwards
the strategy can also be a
<strong><code>TimeoutAwareAggregationStrategy</code></strong> implementation,
supporting the timeout callback, see further below for more details.</p><p>From
<strong>Camel 2.16</strong>: the strategy can also be a
<strong><code>PreCompletionAwareAggregationStrategy</code></strong>
implementation which then runs the completion check in pre-completion mode. See
further below for more details.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>strategyRef</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>A reference to lookup the
<strong><code>AggregationStrategy</code></strong> in the <a shape="rect"
href="registry.html">Registry</a>. From <strong>Camel 2.12</strong> onwards you
can also use a POJO as the <strong><code>AggregationStrategy</code></strong>,
see further below for
details.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>strategyMethodName</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><strong>Camel 2.12:</strong> This option can be used to
explicit declare the method name to use, when using POJOs as the
<strong><code>AggregationStrategy</code></strong>. See further below for more
details.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>strategyMethodAllowNull</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong> If
this option is <strong><code>false</code></strong> then the aggregate method is
not used for the very first aggregation. If this option is
<strong><code>true</code></strong> then <strong><code>null</code></strong>
values is used as the <strong><code>oldExchange</code></stron
g> (at the very first aggregation), when using POJOs as the
<strong><code>AggregationStrategy</code></strong>. See further below for more
details.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>completionSize</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>Number of messages aggregated before the aggregation is
complete. This option can be set as either a fixed value or using an <a
shape="rect" href="expression.html">Expression</a> which allows you to evaluate
a size dynamically - will use <strong><code>Integer</code></strong> as result.
If both are set Camel will fallback to use the fixed value if the <a
shape="rect" href="expression.html">Expression</a> result was
<strong><code>null</code></strong> or
<strong><code>0</code></strong>.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>completionTimeout</code></p></td><td colspan="1"
rowspan="1" c
lass="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>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 shape="rect" href="expression.html">Expression</a> which allows you
to evaluate a timeout dynamically - will use <strong><code>Long</code></strong>
as result. If both are set Camel will fallback to use the fixed value if the <a
shape="rect" href="expression.html">Expression</a> result was
<strong><code>null</code></strong> or <strong><code>0</code></strong>. You
cannot use this option together with
<strong><code>completionInterval</code></strong>, only one of the two can be
used.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>completionInterval</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>A repeating period in millis by which the aggrega
tor will complete all current aggregated exchanges. Camel has a background
task which is triggered every period. You cannot use this option together with
<strong><code>completionTimeout</code></strong>, only one of them can be
used.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>completionPredicate</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>A <a shape="rect"
href="predicate.html">Predicate</a> to indicate when an aggregated exchange is
complete.</p><p>From <strong>Camel 2.15</strong>: if this is not specified and
the <strong><code>AggregationStrategy</code></strong> object implements
Predicate, the <strong><code>aggregationStrategy</code></strong> object
will be used as the
<strong><code>completionPredicate</code></strong>.</p></td></tr><tr><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>completionFromBatchConsumer</code></p></td><td
colspan="1"
rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>This option is if the exchanges are coming
from a <a shape="rect" href="batch-consumer.html">Batch Consumer</a>. Then when
enabled the <a shape="rect" href="aggregator2.html">Aggregator2</a> will use
the batch size determined by the <a shape="rect"
href="batch-consumer.html">Batch Consumer</a> in the message header
<strong><code>CamelBatchSize</code></strong>. See more details at <a
shape="rect" href="batch-consumer.html">Batch Consumer</a>. This can be used to
aggregate all files consumed from a <a shape="rect" href="file2.html">File</a>
endpoint in that given poll.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>forceCompletionOnStop</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.9</strong>
Indicates to complete all current aggr
egated exchanges when the context is stopped</p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><code>completeAllOnStop</code></td><td
colspan="1" rowspan="1" class="confluenceTd"><code>false</code></td><td
colspan="1" rowspan="1" class="confluenceTd"><strong>Camel
2.16:</strong> Indicates to wait to complete all current and partial
(pending) aggregated exchanges when the context is stopped. This also means
that we will wait for all pending exchanges which are stored in
the aggregation repository to complete so the repository is empty
before we can stop.  You may want to enable this when using the memory
based aggregation repository that is memory based only, and do not store
data on disk. When this option is enabled, then the aggregator is waiting to
complete all those exchanges before its stopped, when stopping
CamelContext or the route using it.</td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>eagerCheckCompletion
</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>Whether or not to eager check for completion when a new
incoming <a shape="rect" href="exchange.html">Exchange</a> has been received.
This option influences the behavior of the
<strong><code>completionPredicate</code></strong> option as the <a shape="rect"
href="exchange.html">Exchange</a> being passed in changes accordingly. When
<strong><code>false</code></strong> the <a shape="rect"
href="exchange.html">Exchange</a> passed in the <a shape="rect"
href="predicate.html">Predicate</a> is the <em>aggregated</em> Exchange which
means any information you may store on the aggregated Exchange from
the <strong><code>AggregationStrategy</code></strong> is available for the
<a shape="rect" href="predicate.html">Predicate</a>. When <code>true</code> the
<a shape="rect" href="exchange.html">Exchange</a> passed in the <a shape="rect"
href="predi
cate.html">Predicate</a> is the <em>incoming</em> <a shape="rect"
href="exchange.html">Exchange</a>, which means you can access data from the
incoming Exchange.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>groupExchanges</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>If enabled then Camel will group all
aggregated Exchanges into a single combined
<strong><code>org.apache.camel.impl.GroupedExchange</code></strong> 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 <strong><code>AggregationStrategy</code></strong> yourself.
</p><p><strong>Note:</strong> this option does <strong>not</strong> support
persistent repository with the aggregator. See further below for an example and
mo
re details.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>ignoreInvalidCorrelationKeys</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>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.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>closeCorrelationKeyOnCompletion</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>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
<strong><code>closedCorrelationKeyException</code></strong>
exception. When using this option you pass in a
<strong><code>integer</code></strong> 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.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>discardOnCompletionTimeout</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.5:</strong>
Whether or not exchanges which complete due to a timeout should be discarded.
If enabled then when a timeout occurs the aggregated message will
<strong>not</strong> be sent out but dropped (discarded).</p></td></tr><tr><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>aggregationRepository</code></p></td><td
colspan="1" rowspan="1" class="confluen
ceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>Allows you to plugin you own implementation of
<strong><code>org.apache.camel.spi.AggregationRepository</code></strong> which
keeps track of the current inflight aggregated exchanges. Camel uses by default
a memory based implementation.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>aggregationRepositoryRef</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Reference to lookup a
<strong><code>aggregationRepository</code></strong> in the <a shape="rect"
href="registry.html">Registry</a>.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>parallelProcessing</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>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.</p></td></tr><tr><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>executorService</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>If using
<strong><code>parallelProcessing</code></strong> you can specify a custom
thread pool to be used. In fact also if you are not using
<strong><code>parallelProcessing</code></strong> this custom thread pool is
used to send out aggregated exchanges as well.</p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>executorServiceRef</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Reference to lookup a
<strong><code>executorService</code></strong> in t
he <a shape="rect" href="registry.html">Registry</a></p></td></tr><tr><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>timeoutCheckerExecutorService</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.9:</strong> If using either
of the <strong><code>completionTimeout</code></strong>,
<strong><code>completionTimeoutExpression</code></strong>, or
<strong><code>completionInterval</code></strong> 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.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>timeoutCheckerExecutorServiceRef</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.9:</strong> Reference to
lookup
a <strong><code>timeoutCheckerExecutorService</code></strong> in the <a
shape="rect" href="registry.html">Registry</a></p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>optimisticLocking</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.11:</strong>
Turns on using optimistic locking, which requires the
<strong><code>aggregationRepository</code></strong> being used, is supporting
this by implementing the
<strong><code>org.apache.camel.spi.OptimisticLockingAggregationRepository</code></strong>
interface.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>optimisticLockRetryPolicy</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.11.1:</strong> Allows to
configure retry settings when using optimistic locking.</p></td></tr></tbody
></table></div><h3 id="Aggregator2-ExchangeProperties">Exchange
>Properties</h3><p>The following properties are set on each aggregated
>Exchange:</p><p>confluenceTableSmall</p><div class="table-wrap"><table
>class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1"
>class="confluenceTh"><p>Header</p></th><th colspan="1" rowspan="1"
>class="confluenceTh"><p>Type</p></th><th colspan="1" rowspan="1"
>class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1"
>rowspan="1"
>class="confluenceTd"><p><code>CamelAggregatedSize</code></p></td><td
>colspan="1" rowspan="1" class="confluenceTd"><p><code>int</code></p></td><td
>colspan="1" rowspan="1" class="confluenceTd"><p>The total number of Exchanges
>aggregated into this combined Exchange.</p></td></tr><tr><td colspan="1"
>rowspan="1"
>class="confluenceTd"><p><code>CamelAggregatedCompletedBy</code></p></td><td
>colspan="1" rowspan="1"
>class="confluenceTd"><p><code>String</code></p></td><td colspan="1"
>rowspan="1" class="confluenceTd"><p>Ind
icator how the aggregation was completed as a value of either:
<strong><code>predicate</code></strong>, <strong><code>size</code></strong>,
<strong><code>strategy</code></strong>, <strong><code>consumer</code></strong>,
<strong><code>timeout</code></strong>,
<strong><code>forceCompletion</code></strong> or
<strong><code>interval</code></strong>.</p></td></tr></tbody></table></div><h3
id="Aggregator2-AboutAggregationStrategy">About AggregationStrategy</h3><p>The
<strong><code>AggregationStrategy</code></strong> 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 provi
ded to the aggregator.</p><p>Here are a few
example <strong><code>AggregationStrategy</code></strong> implementations
that should help you create your own custom strategy.</p>
+ class ArrayListAggregationStrategy implements AggregationStrategy { public
Exchange aggregate(Exchange oldExchange, Exchange newExchange) { Object newBody
= newExchange.getIn().getBody(); ArrayList</div>
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