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• Batch resequencing collects messages into a batch, sorts the messages and sends them to their output.
• Stream resequencing re-orders (continuous) message streams based on the detection of gaps between messages.

By default the Resequencer does not support duplicate messages and will only keep the last message, in case a message arrives with the same message expression. However in the batch mode you can enable it to allow duplicates.

Batch Resequencing

The following example shows how to use the batch-processing resequencer so that messages are sorted in order of the body() expression. That is messages are collected into a batch (either by a maximum number of messages per batch or using a timeout) then they are sorted in order and then sent out to their output.

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<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
  <route>
    <from uri="direct:start" />
    <resequence>
      <simple>body</simple>
      <to uri="mock:result" />
      <!-- 
        batch-config can be ommitted for default (batch) resequencer settings
      -->
      <batch-config batchSize="300" batchTimeout="4000" />
    </resequence>
  </route>
</camelContext>

Allow Duplicates

Available as of Camel 2.4

In the batch mode, you can now allow duplicates. In Java DSL there is a allowDuplicates() method and in Spring XML there is an allowDuplicates=true attribute on the <batch-config/> you can use to enable it.

Reverse

Available as of Camel 2.4

In the batch mode, you can now reverse the expression ordering. By default the order is based on 0..9,A..Z, which would let messages with low numbers be ordered first, and thus also also outgoing first. In some cases you want to reverse order, which is now possible.

In Java DSL there is a reverse() method and in Spring XML there is an reverse=true attribute on the <batch-config/> you can use to enable it.

Resequence JMS messages based on JMSPriority

Available as of Camel 2.4

It's now much easier to use the Resequencer to resequence messages from JMS queues based on JMSPriority. For that to work you need to use the two new options allowDuplicates and reverse.

{snippet:id=e1|lang=java|url=camel/trunk/components/camel-jms/src/test/java/org/apache/camel/component/jms/JmsBatchResequencerJMSPriorityTest.java}

Notice this is only possible in the batch mode of the Resequencer.

Stream Resequencing

The next example shows how to use the stream-processing resequencer. Messages are re-ordered based on their sequence numbers given by a seqnum header using gap detection and timeouts on the level of individual messages.

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