Resequencer

Resequencer

The Resequencer from the EIP patterns allows you to reorganise messages based on some comparator. By default in Camel we use an Expression to create the comparator; so that you can compare by a message header or the body or a piece of a message etc.

The following example shows how to reorder the messages so that they 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.

Using the Fluent Builders

So the above example will reorder messages from endpoint direct:a in order of their bodies, to the endpoint mock:result. Typically you'd use a header rather than the body to order things; or maybe a part of the body. So you could replace this expression with

resequencer(header("JMSPriority"))

for example to reorder messages using their JMS priority.

You can of course use many different Expression languages such as XPath, XQuery, SQL or various Scripting Languages.

You can also use multiple expressions; so you could for example sort by priority first then some other custom header

resequencer(header("JMSPriority"), header("MyCustomerRating"))

Using the Spring XML Extensions

For further examples of this pattern in use you could look at the junit test case