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Loopback Mediator

The Loopback Mediator moves messages from the in flow (request path) to the out flow (response path). All the configuration included in the in sequence that appears after the Loopback mediator is skipped.

Info

  • The Loopback mediator is a content-unaware mediator.
  • The messages that have already been passed from the In sequence to the Out sequence cannot be moved to the Out sequence again via the Loopback mediator.

Syntax

The loopback token refers to a <loopback/> element, which is used to skip the rest of the in flow and move the message to the out flow.

<loopback/>

Configuration

As with other mediators, after adding the Loopback mediator to a sequence, you can click its up and down arrows to move its location in the sequence.

Example

This example is a main sequence configuration with two PayloadFactory mediators. Assume you only want to use the first factory but need to keep the second factory in the configuration for future reference. The Loopback mediator is added after the first PayloadFactory mediator configuration to skip the second PayloadFactory mediator configuration. This configuration will cause the message to be processed with the first payload factory and then immediately move to the out flow, skipping the second payload factory in the in flow.

<definitions xmlns="http://ws.apache.org/ns/synapse">
  <sequence name="main">
    <in>
      <payloadFactory>
        <format>
          <m:messageBeforeLoopBack xmlns:m="http://services.samples">
            <m:messageBeforeLoopBackSymbol>
              <m:symbolBeforeLoopBack>$1</m:symbolBeforeLoopBack>
            </m:messageBeforeLoopBackSymbol>
          </m:messageBeforeLoopBack>
        </format>
        <args>
          <arg xmlns:m0="http://services.samples"
            evaluator="xml"
            expression="//m0:symbol/text()"/>
          </args>
      </payloadFactory>

      <loopback/>

      <payloadFactory>
        <format>
          <m:messageAfterLoopBack xmlns:m="http://services.samples">
            <m:messageAfterLoopBackSymbol>
              <m:symbolAfterLoopBack>$1</m:symbolAfterLoopBack>
            </m:messageAfterLoopBackSymbol>
          </m:messageAfterLoopBack>
        </format>
        <args>
          <arg xmlns:m0="http://services.samples"
            evaluator="xml"
            expression="//m0:symbolBeforeLoopBack/text()"/>
        </args>
      </payloadFactory>
    </in>
    <out>
      <send/>
    </out>
  </sequence>
</definitions> 
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