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Loop

The Loop allows for processing a message a number of times, possibly in a different way for each iteration. Useful mostly during testing.

Options

Exchange properties

For each iteration two properties are set on the Exchange. Processors can rely on these properties to process the Message in different ways.

Examples

The following example shows how to take a request from the direct:x endpoint, then send the message repetitively to mock:result. The number of times the message is sent is either passed as an argument to loop(), or determined at runtime by evaluating an expression. The expression must evaluate to an int, otherwise a RuntimeCamelException is thrown.

Using the Fluent Builders

Pass loop count as an argument

{snippet:id=ex1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/LoopTest.java}

Use expression to determine loop count

{snippet:id=ex2|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/LoopTest.java}

Use expression to determine loop count

{snippet:id=ex3|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/LoopTest.java}

Using the Spring XML Extensions

Pass loop count as an argument

{snippet:id=ex1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/loop.xml}

Use expression to determine loop count

{snippet:id=ex2|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/loop.xml}

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

Using copy mode

Available as of Camel 2.8

Now suppose we send a message to "direct:start" endpoint containing the letter A.
The output of processing this route will be that, each "mock:loop" endpoint will receive "AB" as message.

{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/LoopCopyTest.java}

However if we do not enable copy mode then "mock:loop" will receive "AB", "ABB", "ABBB", etc. messages.

{snippet:id=e1|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/LoopNoCopyTest.java}

The equivalent example in XML DSL in copy mode is as follows:

{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/SpringLoopCopyTest.xml}