Loop

The Loop allows to process the a message a number of times and possibly process them in a different way. Useful mostly for testing.

For each iteration two properties are set on the Exchange that could be used by processors down the pipeline to process the Message in different ways.

Property Description
CamelIterationCount Camel 1.x: Total number of iterations to be run
CamelIterationIndex Camel 1.x: Index of the current iteration (0 based)
CamelLoopSize Camel 2.0: Total number of loops
CamelLoopIndex Camel 2.0: Index of the current iteration (0 based)

that could be used by processors down the pipeline 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

from("direct:a").loop(8).to("mock:result");

Use expression to determine loop count

from("direct:b").loop(header("loop")).to("mock:result");

Use expression to determine loop count

from("direct:c").loop().xpath("/hello/@times").to("mock:result");

Using the Spring XML Extensions

Pass loop count as an argument

<route>
  <from uri="direct:a"/>
  <loop>
    <constant>8</constant>
    <to uri="mock:result"/>
  </loop>
</route>

Use expression to determine loop count

<route>
  <from uri="direct:b"/>
  <loop>
    <header>loop</header>
    <to uri="mock:result"/>
  </loop>
</route>

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

Using This Pattern

If you would like to use this EIP Pattern then please read the Getting Started, you may also find the Architecture useful particularly the description of Endpoint and URIs. Then you could try out some of the Examples first before trying this pattern out.

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