ESB as a JMS Consumer

This section describes how to configure WSO2 ESB to listen to a JMS Queue.

Follow the steps below to configure WSO2 ESB to listen to a JMS queue, consume messages, and send them to a HTTP back-end service.

Configure WSO2 ESB with Apache ActiveMQ and set up the JMS listener. For instructions, see Configure with ActiveMQ.
Create a proxy service with the following configuration.To create a proxy service using ESB Tooling, see Working with Proxy Services via ESB Tooling.
```
<proxy xmlns="http://ws.apache.org/ns/synapse" name="JMStoHTTPStockQuoteProxy" transports="jms">
       <target>
           <inSequence>
               <property action="set" name="OUT_ONLY" value="true"/>
           </inSequence>
           <endpoint>
               <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
           </endpoint>
           <outSequence>
               <send/>
           </outSequence>
       </target>
</proxy>
```
You can make the proxy service a JMS listener by setting its transport as jms. Once the JMS transport is enabled for a proxy service, ESB will start listening on a JMS queue with the same name as the proxy service. In the sample configuration above, ESB listens to a JMS queue named JMStoHTTPStockQuoteProxy. To make the proxy service listen to a different JMS queue, define the transport.jms.Destination parameter with the name of the destination queue.
To test this you will need an HTTP back-end service. Deploy the SimpleStockQuoteService and start the Axis2 server.

Place a message into the ActiveMQ queue by executing the following command from <ESB_HOME>/samples/axis2Client folder.

ant stockquote -Dmode=placeorder -Dtrpurl="jms:/JMStoHTTPStockQuoteProxy?transport.jms.ConnectionFactoryJNDIName=QueueConnectionFactory&java.naming.factory.initial=org.apache.activemq.jndi.ActiveMQInitialContextFactory&java.naming.provider.url=tcp://localhost:61616&transport.jms.ContentTypeProperty=Content-Type&transport.jms.DestinationType=queue"

ESB will read the message from the ActiveMQ queue and send it to the back-end service. You will see the following response in the Axis2 Server console:

Fri Dec 16 10:21:11 GST 2016 samples.services.SimpleStockQuoteService  :: Accepted order #1 for : 7424 stocks of IBM at $ 156.74347214873563

Two-way HTTP Back-end Call

In addition to one-way invocations, WSO2 ESB proxy service can listen to the queue, pick up a message and do a two-way HTTP call as well. This is done when the client specifies a replyDestination element when placing a request message to a JMS queue. It allows the response to be delivered to the replyDestination queue specified by the client. The scenario is depicted in the diagram below.

We can have a proxy service similar to the following to simulate a two-way invocation.

<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="Proxy1"
       transports="jms"
       startOnLoad="true"
       trace="disable">
   <description/>
   <target> 
      <inSequence>
         <send>
            <endpoint>
               <address uri="http://localhost:9765/services/t/superqa.com/Axis2Service"/>
            </endpoint>
         </send>
      </inSequence>
      <outSequence>
         <send/>
      </outSequence>
   </target>
   <parameter name="transport.jms.ContentType">
      <rules>
         <jmsProperty>contentType</jmsProperty>
         <default>text/xml</default>
      </rules>
   </parameter>
</proxy>

Defining Content Type of Incoming JMS Messages

By default, WSO2 ESB considers all messages consumed from a queue as a SOAP message. To consider messages consumed from a queue as a different format, define the transport.jms.ContentType parameter with the respective content type as a proxy service parameter. The sample code below

To demonstrate this, we have modified the above configuration as follows to connect to MyJMSQueue queue and read messages as POX messages.

 <proxy xmlns="http://ws.apache.org/ns/synapse" name="JMStoHTTPStockQuoteProxy" transports="jms">
       <target>
           <inSequence>
               <property action="set" name="OUT_ONLY" value="true"/>
               <send>
                   <endpoint>
                       <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
                   </endpoint>
               </send>
           </inSequence>
           <outSequence>
               <send/>
           </outSequence>
       </target>
       <parameter name="transport.jms.ContentType">
           <rules>
               <jmsProperty>contentType</jmsProperty>
               <default>application/xml</default>
           </rules>
       </parameter>
       <parameter name="transport.jms.Destination">MyJMSQueue</parameter>
   </proxy>