JMS Synchronous Invocations : Dual Channel HTTP-to-JMS

The following diagram depicts dual-channel JMS synchronous invocations of the ESB.

The following example code shows configuration of WSO2 ESB for dual-channel JMS synchronous invocations.

<proxy name="StockQuoteProxy" transports="http">
      <target>
          <endpoint>
                  <address uri="jms:/SimpleStockQuoteService?transport.jms.ConnectionFactoryJNDIName=QueueConnectionFactory&amp;                 java.naming.factory.initial=org.apache.activemq.jndi.ActiveMQInitialContextFactory&amp;java.naming.provider.url=tcp://localhost:61616&amp;transport.jms.DestinationType=queue&amp;transport.jms.ReplyDestination=SimpleStockQuoteServiceReply"/>
          </endpoint>
          <inSequence>
              <property action="set" name="transport.jms.ContentTypeProperty" value="Content-Type" scope="axis2"/>
          </inSequence>
          <outSequence>
              <property action="remove" name="TRANSPORT_HEADERS" scope="axis2"/>
              <send/>
          </outSequence>
      <target>
      <publishWSDL uri="file:repository/conf/sample/resources/proxy/sample_proxy_1.wsdl"/>
</proxy>

The message flow of the sample code is as follows:

1. The ESB proxy service accepts messages via HTTP and places them in SimpleStockQuoteService JMS queue.
   
2. The back-end consumes these messages from the queue and places response messages in the SimpleStockQuoteServiceReply queue.
   
3. When a reply is available in the SimpleStockQuoteServiceReply queue, the ESB proxy will pick the response message and send it as the response to the client via HTTP connection.

To send a HTTP message to the ESB proxy service, execute following command from <ESB_HOME>/sample/axis2Client directory. 

ant stockquote -Daddurl=http://localhost:8280/services/StockQuoteProxy -Dmode=placeorder -Dsymbol=MSFT

To co-relate request and response JMS messages, the ESB uses a JMS correlation ID internally. For more information, refer to http://www.eaipatterns.com/RequestReplyJmsExample.html. 

Since this is a two-way invocation, the inSequence does not have the configuration <property action="set" name="OUT_ONLY" value="true"/>. 

The response queue name is defined using transport.jms.ReplyDestination parameter in the JMS connection URL.