How the Message Translator EIP Works

If you need to connect two applications, the main impotent point is both applications should use common data type compatible with each other. To facilitate this, some intermediary translation should happen between the sender and receiver. The translator in between  should change the context of the message form one data type to another.

This blog post explains how ESB Message Translator EIP works.

To explain this EIP pattern we use echo service hosted in application server connect with ESB proxy service. In here sender sends the request in one format and the translator transforms that message compatible with the back end service. Here we used the payload factory mediator type “xml “and format the message  coming in to in-sequence compatible with the back end service hosted in application server. The echo service deployed in application  server receives the message compatible with it. 

 Now lets see the how to implement this pattern.

1. Create a proxy service in ESB as follows.

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="translatorProxy"
       transports="https,http"
       statistics="disable"
       trace="disable"
       startOnLoad="true">
   <target>
      <inSequence>
         <log level="full"/>
         <log level="custom">
            <property xmlns:p="http://service.carbon.wso2.org"
                      name="Value"
                      expression="//p:string"/>
         </log>
         <payloadFactory media-type="xml">
            <format>
               <p:echoString xmlns:p="http://echo.services.core.carbon.wso2.org">
                  <in>$1</in>
               </p:echoString>
            </format>
            <args>
               <arg xmlns:p="http://service.carbon.wso2.org"
                    evaluator="xml"
                    expression="//p:string"/>
            </args>
         </payloadFactory>
         <log level="full"/>
         <send>
            <endpoint>
               <address uri="http://localhost:9764/services/echo"/>
            </endpoint>
         </send>
      </inSequence>
      <outSequence>
         <send/>
      </outSequence>
      <faultSequence>
         <log level="full">
            <property name="MESSAGE" value="Executing default &#34;fault&#34; sequence"/>
            <property name="ERROR_CODE" expression="get-property('ERROR_CODE')"/>
            <property name="ERROR_MESSAGE" expression="get-property('ERROR_MESSAGE')"/>
         </log>
         <drop/>
      </faultSequence>
   </target>
   <description/>
</proxy>  

                            

2. Open "SOAPUI"/"Try it" Client and send the below message to the ESB proxy

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:p="http://service.carbon.wso2.org">

<soapenv:Body>
<p:string>testString</p:string>

</soapenv:Body>

</soapenv:Envelope>

3. After sending the request, the payload factory mediator in ESB proxy  converts the request compatible with the receiver. 

The message format compatible with the receiver is as follows

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:p="http://service.carbon.wso2.org">

<soapenv:Body>

<p:echoString xmlns:p="http://echo.services.core.carbon.wso2.org">

<in xmlns="http://ws.apache.org/ns/synapse">testString</in>

</p:echoString>

</soapenv:Body>

</soapenv:Envelope>