I posted before about how to create a mock service when you have a JDK 1.6 or higher available (for the interested you can find it here). Of course there are a lot more options to mock web services (one I used often is the option supplied by SoapUI). This post shows a way to mock a web service by using a WSO2 Proxy Service.

The way to do this is by using the PayloadFactory mediator. There is also an example of its general usage here.

To use this mediator for mocking a service see the following configuration:

<proxy xmlns="http://ws.apache.org/ns/synapse" name="MyMockService" transports="https,http" statistics="disable" trace="disable" startOnLoad="true">
   <target>
      <inSequence>
         <payloadFactory>
            <format>
               <ns0:myMessage xmlns:ns0="http://www.pascalalma.net/test">
                  <ns0:address>
                     <ns0:postalcode>$1</ns0:postalcode>
                     <ns0:number>$2</ns0:number>
                  </ns0:address>
               </ns0:myMessage>
            </format>
            <args>
               <arg xmlns:sel="http://www.pascalalma.net/input" expression="//sel:postalcode"/>
               <arg xmlns:sel="http://www.pascalalma.net/input" expression="//selectie:mynumber"/>
            </args>
         </payloadFactory>
         <header name="To" action="remove"/>
         <property name="RESPONSE" value="true" scope="default" type="STRING"/>
         <send/>
      </inSequence>
   </target>
   <description></description>
</proxy>    

The important parts here are the following:

Inside the ‘format’ element of the ‘PayloadFactory’ mediator we define inline the XML message we want to use as a response on every incoming request. In this inline XML we can use the syntax ‘$1′, ‘$2′ etc to refer to arguments we define after the ‘format’ element. These ‘arg’ elements contain XPath expressions which are executed against the incoming message. This way you can make the result of the mock service a little more dynamic and that way more useful in your testcases.

The other important parts are the ‘header‘ element and the ‘property‘ element. These lines avoids the proxy to wait for a response in the outSequence which would normally be the case with a proxy service.