Use callout mediator within a fault sequence?

Reference: Multiple endpoints and conditionals?



I have sequences setup on a proxy that change the payload, and send to a service for validation (schema validation not possible).  If the message is deemed valid, it is then sent to JMS.  If not, a soap fault is returned to the original caller.  If the JMS service is down, I need to pass the request to a third service to process the message.



If I try to use a callout mediator within the fault sequence, it looks like the mediator is not initialized (synapsecontext).  I get a stacktrace as follows:



ERROR CalloutMediator Error invoking service : http://localhost:8280/soap/BypassJMS with action : urn:BypassJMS

java.lang.NullPointerException

  at org.apache.synapse.mediators.builtin.CalloutMediator.mediate(CalloutMediator.java:100)

  at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:58)

  at org.apache.synapse.mediators.filters.FilterMediator.mediate(FilterMediator.java:95)

  at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:58)

  at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:125)

  at org.apache.synapse.mediators.MediatorFaultHandler.onFault(MediatorFaultHandler.java:79)

  at org.apache.synapse.FaultHandler.handleFault(FaultHandler.java:94)

  at org.apache.synapse.core.axis2.ProxyServiceMessageReceiver.receive(ProxyServiceMessageReceiver.java:187)

  at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:170)

  at org.apache.axis2.transport.http.HTTPTransportUtils.processHTTPPostRequest(HTTPTransportUtils.java:275)

  at org.apache.synapse.transport.nhttp.ServerWorker.processPost(ServerWorker.java:244)

  at org.apache.synapse.transport.nhttp.ServerWorker.run(ServerWorker.java:185)

  at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)

  at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

  at java.lang.Thread.run(Unknown Source)



At first I thought that maybe mediators inside of a filter weren't recursively initialized, but that can be ruled out because the in sequence does the same thing successfully.



A psuedo-code version of the proxy looks like this



<proxy>

  <target>

    <inSequence>

      <script>alter payload</script>

      <callout serviceURL="to validate"><source /><target /></callout>

      <filter to check response from callout>

        <then>

          <script>restore payload</script>

          <callout serviceURL="to send to jms"><source /><target /></callout>

          <!-- above will send to fault sequence because no response -->

        </then>

        <else>

          <script>Get and cleanup error message</script>

          <makefault />

          <property name="response" value="true"/>

          <header name="to" action="remove" />

          <send />

        </else>

      </filter>

    </inSequence>

    <outSequence>

      <send />

    </outSequence>

    <faultSequence>

      <script>

        Determine if faulting because of validation, or JMS

        If error invoking service of type jms:/

          (we know validation successful)

          If due to error creating connection (ActiveMQ was down before call)

            then Set property to bypass storing on queue

          else if due to error creating a producer or sending (ActiveMQ was down before call)

            then Set proprety to bypass storing on queue

          else if due to error JMSException: Connection reset (ActiveMQ died after call began)

            then set property to bypass storing on queue

          else if due to input stream for incoming message is null (ActiveMQ has no response, and this is a timeout)

            then set payload to indicate message validated and sent to queue for processing

          else (some other jms error)

            set property to make fault

          end if

        else

        If error invoking service of type http://

          if error related to Validate callout

            then set property to make fault and message indicating validation error.

          else if error related to bypassing jms

            then set property to make fault and message indicating processing error.

          else (unrecognized error)

            then set property to make fault and message of unhandled error.

          end if

        else

        (all other errors)

          set property to make fault, and dump the error_detail

      </script>

      <filter make fault?>

        <makefault />

      </filter>

      <filter bypassing jms?>

        <callout serviceURL="bypassjms">

        <script>

          set payload to indicate message validated and processed

        </script>

      </filter>

      <send>

    </faultSequence>

  </target>

</proxy>



I've attached my synapse.xml and source for test client (validatedcheckin.java) and modified ant file (build.xml of axis2client samples. This requires ActiveMQ, and the synapse.xml includes additional proxies to emulate calling webservice on another server.  Transports for JMS sender need to be enabled in axis2.xml but  otherwise, should be default setup.  Can test by loading ActiveMQ, then ESB, then stopping ActiveMQ and running test client (ant validatedcheckin)



-Lucas