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The Filter Mediator can be used for filtering messages based on an XPath or JSON Path. There are two modes of operation.

  1. If the user only specifies the XPath or JSON Path, it will be evaluated as true or false.
  2. If the user specifies a regular expression as well, the string returned from evaluating the XPath or JSON Path will be matched against the regular expression.

In both modes, if the evaluation of expression returns true, the child mediators will be executed.

The Filter Mediator closely resembles the "If-else" control structure.



Syntax

<filter (source="[XPath|json-eval(JSON Path)]" regex="string") | xpath="[XPath|json-eval(JSON Path)]">
   mediator+
</filter>

The Filter Mediator either tests the given XPath/JSON Path expression as a Boolean expression, or matches the evaluation result of a source XPath/JSON Path expression as a string against the given regular expression. If the test succeeds, the Filter Mediator will execute the enclosed mediators in sequence.

One could also use this mediator to handle a failure scenario as well. In this case, the configuration will be as follows:

<filter (source="[XPath|json-eval(JSON Path)]" regex="string") | xpath="[XPath|json-eval(JSON Path)]">
   <then [sequence="string"]>
     mediator+
   </then>
   <else [sequence="string"]>
     mediator+
   </else>
</filter>

In this case, the Filter condition remains the same and the succeeded messages will be mediated using the the set of mediators enclosed in the "then" element in sequence, while failed messages will be mediated using the set of mediators enclosed in the "else" element in sequence.


UI Configuration

Here are the configuration options related to the Filter Mediator:

  • Specify As - Specifies whether you give the condition as an XPath or a Regular expression.
  • XPath - XPath or JSON Path expression if you selected "XPath" for "Specify As". When specifying a JSON Path, use the format json-eval(<JSON_PATH>), such as json-eval(getQuote.request.symbol).
  • Source- Expression to locate the value that matches the regular expression that you can define below.

    Tip

    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 or JSON Path expression.

  • Regex - Regular expression to match the source value.

Note

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


Example

<filter source="get-property('To')" regex=".*/StockQuote.*">
      <then>
          <send/>
      </then>
      <else>
          <drop/>
      </else>
</filter>

In this example, the Filter will get the To header value and match it against the given regular expression. If this evaluation returns true, it will send the message. If the evaluation returns false, it will drop the message.

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