How to kick off a mule flow to read messages from a JMS queue using an HTTP endpoint

Question

I basically have two flows :

1. HTTP Inbound endpoint receives batch XML, splits to individual pieces and stages it to a JMS queue.
2. Reads the staged XMLs from the JMS queue and processes the messages.

I need to control the execution of flow 2 above using a Rest call (i.e) flow 2 should run only when an HTTP inbound call is received. I am using Mule version 3.2.2

Here are the flows:

         <flow name="flow-stage-input">
           <http:inbound-endpoint   host="localhost" 
                        port=   "8082" 
                        path=   "test/order"
                        exchange-pattern=   "request-response"
                                    >

           </http:inbound-endpoint>
          <object-to-string-transformer></object-to-string-transformer>
          <splitter evaluator="xpath" expression="//Test/TestNode" enableCorrelation="ALWAYS"/>
          <custom-transformer class="org.testing.transformers.DocumentToString"></custom-transformer>

          <pooled-component>
                <spring-object bean="receiver"></spring-object>
          </pooled-component>

          <!-- DECIDE SUCCESS OR FAILURE --> 
          <choice>
                <when expression="//Test/TestNode" evaluator="xpath">
            <jms:outbound-endpoint queue="stagingQueue" exchange-pattern="one-way" connector-ref="jmsConnector" />
            </when>
            <otherwise>
                <logger message="Skipped staging message due to errors" level="ERROR" /> 
            </otherwise>
          </choice>
          <collection-aggregator></collection-aggregator>
          <custom-transformer class="org.testing.transformers.ListOfStringsToString"></custom-transformer>
          <!-- RESPONSE SENT BACK TO CALLER -->
        </flow>




        <flow name="flow-process-jms-input" > 
           <jms:inbound-endpoint  queue="stagingQueue" exchange-pattern="one-way" connector-ref="jmsConnector" />
           <pooled-component>
            <spring-object bean="processor"></spring-object>
           </pooled-component>
           <!-- DECIDE SUCCESS OR FAILURE  -->
           <choice>
                 <when expression="//ErrorCondition/Path" evaluator="xpath">
                <jms:outbound-endpoint queue="errorQueue" exchange-pattern="one-way" connector-ref="jmsConnector" />
             </when>
             <otherwise>
                <logger message="Message processed successfully" level="ERROR" /> 
             </otherwise>
           </choice>
         </flow>

Answer 1

Use a Groovy script in flow 2 to request one JMS message from the queue using:

muleContext.client.request("jms://stagingQueue", 0)

This will return null if the queue was empty otherwise a Mule message containing the JMS message.