Loop

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

Pass loop count as an argument

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.

Using while mode

Available as of Camel 2.17

The loop can act like a while loop that loops until the expression evaluates to false or null.

For example the route below loops while the length of the message body is 5 or less characters. Notice that the DSL uses loopDoWhile.

from("direct:start")
    .loopDoWhile(simple("${body.length} <= 5"))
        .to("mock:loop")
        .transform(body().append("A"))
    .end()
    .to("mock:result");

And the same example in XML:

    <route>
      <from uri="direct:start"/>
      <loop doWhile="true">
        <simple>${body.length} &lt;= 5</simple>
        <to uri="mock:loop"/>
        <transform>
          <simple>A${body}</simple>
        </transform>
      </loop>
      <to uri="mock:result"/>
    </route>

Notice in XML that the while loop is turned on using the doWhile attribute.