Mule: Transport of Larger Responses in CXF

Upon calling a remote web service via a CXF endpoint in Mule I was presented with the following error:

Caused by: javax.xml.bind.UnmarshalException
 - with linked exception:
[com.ctc.wstx.exc.WstxIOException: Connection reset]
        at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.handleStreamException(UnmarshallerImpl.java:426)
        at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal0(UnmarshallerImpl.java:362)
        at com.sun.xml.bind.v2.runtime.unmarshaller.UnmarshallerImpl.unmarshal(UnmarshallerImpl.java:339)
        at org.apache.cxf.jaxb.JAXBEncoderDecoder.unmarshall(JAXBEncoderDecoder.java:537)
        ... 96 more

At first, I thought either my request or the response from the remote server was malformed XML since the exception class and stack trace seems to suggest a marshalling problem. On the other hand, the exception mentions a connection reset.

To help spare you kind readers the details of my investigation, it turns out the above problem only manifested itself when a large amount of data was being transferred between the services.

The Mule CXF Transport documentation lists an attribute, mtomEnabled, that can be enabled on the definition of the outbound endpoint for the remote service:

    <cxf:endpoint name="remoteService"
                  address="http://constanza.com/service/architectureService"
                  clientClass="com.costanza.ArchitectureService"
                  wsdlPort="ArchitectureServicePort"
                  wsdlLocation="http://constanza.com/service/architectureService?wsdl"
                  operation="getBlueprint"
                  mtomEnabled="true"/>

The attribute turns on the SOAP Message Transmission Optimization Mechanism which encodes the response payload for travel between the services. The Mule documentation refers to this allowing for data to be sent as an attachment. At the very least it tells CXF to be on the look out or to handle a potentially large response.