Message Translator

Typically, different applications use different data types. Therefore, for two applications to successfully communicate, you should intermediately translate the messages that pass from one application to the data type compatible with the receiving application. A translator changes the context of a message from one interface to another, allowing messages to adhere to message context rules of the back-end service.

The Message Translator EIP is responsible for message translating to ensure compatibility between applications supporting different data types.

The following sections explain how you can implement a sample scenario of this EIP using the ESB profile of WSO2 EI. 

Sample scenario

The example scenario depicts an inventory of stocks. It illustrates how the sender sends a request in one format, which is then transformed into another format compatible with the receiver. The format of the request is as follows:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ser="http://services.samples" xmlns:xsd="http://services.samples/xsd">
   <soapenv:Header>    
   </soapenv:Header> 
   <soapenv:Body>
        <ser:Code>foo</ser:Code>
   </soapenv:Body>
</soapenv:Envelope>

 The message format compatible with the receiver is as follows:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ser="http://services.samples" xmlns:xsd="http://services.samples/xsd">
   <soapenv:Header/>
   <soapenv:Body>
      <ser:getQuote>
         <!--Optional:-->
         <ser:request>
            <!--Optional:-->
            <ser:symbol>foo</ser:symbol>
         </ser:request>
      </ser:getQuote>
   </soapenv:Body>
</soapenv:Envelope>

All requests in the first format should be translated to the second by the ESB profile of WSO2 EI. 

<?xml version="1.0" encoding="UTF-8"?>
<proxy name="message-translator-proxy" startOnLoad="true" transports="http https"
    xmlns="http://ws.apache.org/ns/synapse">
    <target>
        <inSequence>
            <!-- Will transform the incoming message to the format specified below -->
            <payloadFactory media-type="xml">
                <format>
                    <m:getQuote
                        xmlns:m="http://services.samples">
                        <m:request>
                            <m:symbol>$1</m:symbol>
                        </m:request>
                    </m:getQuote>
                </format>
                <args>
                    <arg evaluator="xml" expression="//m0:Code"
                        xmlns:m0="http://services.samples"/>
                    </args>
                </payloadFactory>
                <send>
                    <endpoint>
                        <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
                    </endpoint>
                </send>
            </inSequence>
            <outSequence>
                <respond/>
            </outSequence>
            <faultSequence/>
        </target>
    </proxy>

Setting up the sample scenario

Follow the below instructions to simulate this sample scenario.

Executing the sample

Send the following request to the ESB using SOAP UI (or any other SOAP client).

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ser="http://services.samples" xmlns:xsd="http://services.samples/xsd">
   <soapenv:Header>    
   </soapenv:Header> 
   <soapenv:Body>
        <ser:Code>foo</ser:Code>
   </soapenv:Body>
</soapenv:Envelope>

Analyzing the output

After sending the request to the ESB profile of WSO2 EI through the client, notice that the request is successfully generated in the stock quote server. 

samples.services.SimpleStockQuoteService :: Generating quote for : foo