This documentation is for WSO2 Enterprise Service Bus version 4.8.0 . View documentation for the latest release.
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The Iterate Mediator implements the Splitter enterprise integration pattern and splits the message into a number of different messages derived from the parent message by finding matching elements for the XPath expression specified. New messages are created for each and every matching element and processed in parallel (default behavior) using either the specified sequence or endpoint. Created messages can also be processed sequentially by setting the optional sequential attribute to true. The original message can be continued or dropped depending on the boolean value of the optional continueParent attribute. The Iterate mediator is similar to the Clone mediator, with the difference being that the Iterate mediator splits a message into different parts, whereas the Clone mediator makes multiple identical copies of the message.

The responses will not necessarily be aggregated in the same order that the requests were sent, even if the sequential attribute is set to true.

The preservePayload attribute specifies if the original message should be used as a template when creating the split messages, and defaults to false, in which case the split messages would contain the split elements as the SOAP body.

The optional id attribute can be used to identify the iterator which created a particular split message when nested iterate mediators are used. This is particularly useful when aggregating responses of messages that are created using nested iterate mediators.



Syntax

<iterate [sequential=(true | false)] [continueParent=(true | false)] [preservePayload=(true | false)] (attachPath="xpath")? expression="xpath">
   <target [to="uri"] [soapAction="qname"] [sequence="sequence_ref"] [endpoint="endpoint_ref"]>
     <sequence>
       (mediator)+
     </sequence>?
     <endpoint>
       endpoint
     </endpoint>?
   </target>+
</iterate>

UI Configuration

The Iterate Mediator can be configured with the following options:

  • Iterate ID - Can be used to identify messages created by the iterate mediator. Useful when defining nested iterate mediators.
  • Sequential Mediation - Specifies whether split messages should be processed sequentially (True) or in parallel (False). Default value is "false" (parallel processing).
  • Continue Parent -Specifies whether the original message should be continued or dropped.
    • True
    • False

      Tip

      This is default to false.

  • Preserve Payload -Specifies whether the original message should be used as a template when creating the split messages.
    • True
    • False

      Tip

      This is default to false.

  • Iterate Expression - XPath expression that matches the elements, which you want to split the message from.
  • Attach Path - To form new messages, you can specify an XPath expression for elements that the split elements are attached to (as expressed in Iterate expression).

You can click the "Namespaces" link to add namespaces if you are providing an expression. You will be provided another panel named "Namespace Editor," where you can provide any number of namespace prefixes and URL that you have used in the XPath expression.

Each Iterate Mediator has its own Target by Default

Here, you can prepare a message to be sent to an endpoint or mediated through some more sequences.

  • SOAP Action - The SOAP action of the message.
  • To Address - The target endpoint address.
  • Sequence - Mediates the message through a sequence. You can either pick a named sequence from the registry or define an anonymous sequence by adding mediators to the current Target mediator as children.
  • Endpoint -Sends the message to an endpoint. Here you can pick a named endpoint from the registry or keep the endpoint as anonymous.

    You can add in the Endpoint panel that can be accessed from the Manage-> Mediation-> Working with Endpoints menu in the left hand side menu bar.

You can configure the Mediator using XML. Click on "switch to source view" in the "Mediator" window.


Example

<iterate expression="//m0:getQuote/m0:request" preservePayload="true"
         attachPath="//m0:getQuote"
         xmlns:m0="http://services.samples">
    <target>
        <sequence>
            <send>
                <endpoint>
                    <address
                        uri="http://localhost:9000/services/SimpleStockQuoteService"/>
                </endpoint>
            </send>
        </sequence>
    </target>
</iterate>

In this scenario, the Iterate Mediator splits the messages into parts and processes them asynchronously. See also Splitting Messages into Parts and Processing in Parallel (Iterate/Aggregate).


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