Using the ESB as a JMS Consumer

This section describes how to configure the ESB Profile of WSO2 Enterprise Integrator (WSO2 EI) to listen to a JMS Queue.

One-way messaging

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

1. Configure the ESB Profile of WSO2 EI with Apache ActiveMQ and set up the JMS listener. For instructions, see Configure with ActiveMQ.

2. Create a proxy service with the following configuration. To create a proxy service using Tooling, see Working with Proxy Services via 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/>
          </target>
   </proxy>

   Proxy Service Configuration

   The OUT_ONLY property is set to true to indicate that the message exchange is one-way.

   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, the ESB Profile of WSO2 EI starts listening on a JMS queue with the same name as the proxy service.

   In the sample configuration above, the ESB Profile of WSO2 EI 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. For details, see below.

3. To test this scenario you need an HTTP back-end service. Deploy the SimpleStockQuoteService and start the Axis2 server. 

4. Place a message in the ActiveMQ queue by executing the following command from the <EI_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"

   The ESB Profile of WSO2 EI will read the message from the ActiveMQ queue and send it to the back-end service. You will see the following response on 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, the proxy service can listen to the queue, pick up a message and do a two-way HTTP call as well. It allows the response to be delivered to a queue specified by the client. This is done by specifying a ReplyDestination element when placing a request message to a JMS queue. The scenario is depicted in the diagram below.

<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="JMStoHTTPStockQuoteProxy1"
       transports="jms"
       startOnLoad="true"
       trace="disable">
   <description/>
   <target> 
      <inSequence>
         <send>
            <endpoint>
               <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
            </endpoint>
         </send>
      </inSequence>
      <outSequence/>
   </target>
   <parameter name="transport.jms.ContentType">
      <rules>
         <jmsProperty>contentType</jmsProperty>
         <default>text/xml</default>
      </rules>
   </parameter>
</proxy>

ant stockquote -Dsymbol=WSO2 -Dtrpurl="jms:/JMStoHTTPStockQuoteProxy1?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&transport.jms.ReplyDestination=ResponseQueue" 

Defining the content type of incoming JMS messages

By default, the ESB Profile of WSO2 EI considers all messages consumed from a queue as SOAP messages. 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. 
 
To demonstrate this, let's modify the above configuration as follows:

 <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/>
       </target>
       <parameter name="transport.jms.ContentType">
           <rules>
               <jmsProperty>contentType</jmsProperty>
               <default>application/xml</default>
           </rules>
       </parameter>
       <parameter name="transport.jms.Destination">MyJMSQueue</parameter>
   </proxy>