Working with ESB XSLT Mediator

What is ESB XSLT Mediator ? 

ESB XLST Mediator supports mediates the messages  when there are dynamic (not predefined/ not static) request for  ESB proxy. The XLST  mediator applies specified XLST transformation to a selected element of current message payload.

Working with XSLT Mediator

This blog post explains how XSLT mediator works, with a simple example.

Let's assume we have a simple calculator service which defines to  work only for "a" and "b" payloads for all four  operations. Assume this service is hosted in WSO2 Application server.

<add>
         <a>?</a>
         <b>?</b>
 </add>

<divide>        
         <a>?</a>
         <b>?</b>
</divide>

<multiply>        
         <a>?</a>
         <b>?</b>
</multiply>

<subtract>
         <a>?</a>
         <b>?</b>
 </subtract>

But what happens if we give payloads as "c" and "d" ? The calculator service won't identify the payloads and give us error response. As a solution for this we can use  ESB XSLT mediator.

This is the created XSLT file for solve  the above problem and save that in ESB local entries.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:p="http://ws.myeclipseide.com" version="1.0">
      <xsl:output method="xml" encoding="utf-8" indent="yes"></xsl:output>
      <xsl:template match="p:add">
         <p:addition xmlns="http://ws.apache.org/ns/synapse">
            <p:c>
               <xsl:value-of select="p:a"></xsl:value-of>
            </p:c>
            <p:d>
               <xsl:value-of select="p:b"></xsl:value-of>
            </p:d>
         </p:addition>
      </xsl:template>
   </xsl:stylesheet>

Please note this XSLT  representation only for "add" operation.

Create a proxy service in ESB by adding XSLT mediator as follows.

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="testR"
       transports="https,http"
       statistics="disable"
       trace="disable"
       startOnLoad="true">
   <target>
      <inSequence>
         <xslt key="xsltNew"/>
         <send>
            <endpoint>
               <address uri="http://localhost:8280/services/Calculator/"/>
            </endpoint>
         </send>
      </inSequence>
      <outSequence>
         <send/>
      </outSequence>
   </target>
   <publishWSDL uri="http://localhost:9764/services/Calculator?wsdl"/>
   <description/>
</proxy>

Now create a new project in SoapUI by adding the WSDL of the created calculator  service.

Invoke the calculator service by sending the payloads as "c" and "d". Now the requests are receiving to ESB as "c" and "d" . The XSLT mediator in ESB proxy converts this to "a"and "b" and send to the Application server where the calculator service is hosted. Inside Application  server the calculations are  done and the respond is send back to the ESB. Then the XSLT mediator in ESB Proxy service understands that, this is the the response for "c" and "d" and it send the answer to the client.