About messageType and JIRA connector - wso2-esb

Question

I have two proxy services for testing purpose that connects with JIRA using JIRA Connector. First one, accepting "application/json" payload:
<proxy name="PruebaJIRA_01" startOnLoad="true" trace="disable" transports="https http">
<description/>
<target>
<inSequence>
<log level="full"/>
<jira.init>
<username>xxxxxx</username>
<password>xxxxxx</password>
<uri>http://gea-jira.its.ute.com/jiragea</uri>
</jira.init>
<property expression="json-eval($.consulta)" name="query"/>
<jira.searchJira>
<query>{$ctx:query}</query>
</jira.searchJira>
<log level="full"/>
<respond/>
</inSequence>
</target>
</proxy>
The second one, accepting "text/xml" payload:
<proxy name="PruebaJIRA_02" startOnLoad="true" trace="disable" transports="https http">
<description/>
<target>
<inSequence>
<property name="messageType" scope="axis2" value="application/json"/>
<log level="full"/>
<jira.init>
<username>xxxxxx</username>
<password>xxxxxx</password>
<uri>http://gea-jira.its.ute.com/jiragea</uri>
</jira.init>
<property expression="//root/consulta" name="query"/>
<jira.searchJira>
<query>{$ctx:query}</query>
</jira.searchJira>
<log level="full"/>
<respond/>
</inSequence>
</target>
</proxy>
It seems that JIRA connector only accept JSON incoming data, so in the second one I have a "messageType" conversion at the top of the sequence.
Both services run OK, but the question is: Why is the second proxy working if I am using an xpath expression?
I am using wso2 ESB 4.9.0.
Thanks in advance.

Answer 1

ESB receives disparate message formats from different clients and systems, because of this ESB required a canonical message format inside the ESB to do all the message mediation tasks. Because of this the message builder used to convert the incoming messages into a canonical format. The canonical format using inside the ESB is SOAP. So surely your XPATH expression works with the soap message.
MessageType property used to select correct message formatter and the message formatter is used to build the outgoing stream from the proxy.
More Info - demystifying-wso2-esb-pass-through-transport /
Working with Message Builders and Formatters