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A JMS synchronous invocation takes place when a JMS producer receives a response to a JMS request produced by it when invoked. The ESB Profile of WSO2 Enterprise Integrator (WSO2 EI) uses an internal JMS correlation ID to correlate the request and the response. See JMS Request/Reply Example for more information.

JMS synchronous invocations are further explained in the following use case.

Use case   

When the proxy service named SMSSenderProxy receives an HTTP request, it publishes that request in a JMS queue named SMSStore. Another proxy service named SMSForwardProxy subscribes to messages published in this queue and forwards them to a back-end service named SimpleStockQuoteService. When this back-end service returns an HTTP response, internal ESB logic is used to save that message as a JMS message in a JMS queue named SMSReceiveNotification. Then this response is taken from the SMSReceiveNotification queue and delivered to the client as an HTTP message using internal ESB logic.

The correlation between request and response:

Note that the message that is passed to the back-end service contains the JMS message ID. However, the back-end service is required to return the response using the JMS correlation ID. Therefore, the back-end service should be configured to copy the message ID from the request (the value of the JMSMessageID header) to the correlation ID of the response (using the JMSCorrelationID header).

The following sub sections explain how to execute this use case. Here, the Message Broker Profile of WSO2 EI is used as the JMS broker.

Prerequisites

  • Install WSO2 Enterprise Integrator. For information on how you can install, see the Installing the Product.
  • Deploy the sample back-end service.

    In this example, the SimpleStockQuoteService serves as the back-end service and receives the message from the SMSForwardProxy proxy service via the JMS transport. The response sent by the SimpleStockQuoteService is published in the SMSReceiveNotificationStore queue that is set as the value of the transport.jms.ReplyDestination parameter of the SMSSenderProxy proxy service. This allows the SMSSenderProxy to pick the response and deliver it to the client. Follow the steps below to build and deploy the SimpleStockQuoteService:

    1. Open a command prompt (or a shell in Linux) and go to the <EI_HOME>/samples/axis2Server/src/SimpleStockQuoteService directory.
    2. Run ant

  • Follow the steps below to enable the JMS transport of the ESB Profile to communicate with the Message Broker profile:

    1. Edit the <EI_HOME>/conf/axis2/axis2.xml file, find the commented <transport receiver> block and uncomment it as follows:

       <!--Uncomment this and configure as appropriate for JMS transport support with WSO2 MB 2.x.x -->
         <transportReceiver name="jms" class="org.apache.axis2.transport.jms.JMSListener">
             <parameter name="myTopicConnectionFactory" locked="false">
                <parameter name="java.naming.factory.initial" locked="false">org.wso2.andes.jndi.PropertiesFileInitialContextFactory</parameter>
                 <parameter name="java.naming.provider.url" locked="false">conf/jndi.properties</parameter>
                 <parameter name="transport.jms.ConnectionFactoryJNDIName" locked="false">TopicConnectionFactory</parameter>
                 <parameter name="transport.jms.ConnectionFactoryType" locked="false">topic</parameter>
             </parameter>
       
             <parameter name="myQueueConnectionFactory" locked="false">
                 <parameter name="java.naming.factory.initial" locked="false">org.wso2.andes.jndi.PropertiesFileInitialContextFactory</parameter>
                 <parameter name="java.naming.provider.url" locked="false">conf/jndi.properties</parameter>
                 <parameter name="transport.jms.ConnectionFactoryJNDIName" locked="false">QueueConnectionFactory</parameter>
                <parameter name="transport.jms.ConnectionFactoryType" locked="false">queue</parameter>
             </parameter>
       
             <parameter name="default" locked="false">
                 <parameter name="java.naming.factory.initial" locked="false">org.wso2.andes.jndi.PropertiesFileInitialContextFactory</parameter>
                 <parameter name="java.naming.provider.url" locked="false">conf/jndi.properties</parameter>
                 <parameter name="transport.jms.ConnectionFactoryJNDIName" locked="false">QueueConnectionFactory</parameter>
                 <parameter name="transport.jms.ConnectionFactoryType" locked="false">queue</parameter>
             </parameter>
         </transportReceiver>
    2. Uncomment the following <transport sender> block for JMS in the same file:

      <!-- uncomment this and configure to use connection pools for sending messages-->
      <transportSender name="jms" class="org.apache.axis2.transport.jms.JMSSender"/>

      For more information on the JMS configuration parameters used in the code segments above, see JMS Connection Factory Parameters.

    3. Open the <EI_HOME>/conf/jndi.properties file and update the connection factories and queues as follows:

      # register some connection factories
      # connectionfactory.[jndiname] = [ConnectionURL]
      connectionfactory.QueueConnectionFactory = amqp://admin:[email protected]/carbon?brokerlist='tcp://localhost:5675'
      
      # register some queues in JNDI using the form
      # queue.[jndiName] = [physicalName]
      queue.SMSStore=SMSStore
      queue.SMSReceiveNotificationStore=SMSReceiveNotificationStore
    4. Copy the following JARs from the <EI_HOME>/wso2/broker/client-lib folder to the <EI_HOME>/lib folder.
      • andes-client-3.2.19.jar
      • geronimo-jms_1.1_spec-1.1.0.wso2v1.jar
      • org.wso2.securevault-1.0.0-wso2v2.jar

  • Start the Message Broker Profile. For information on how to start the Message Broker Profile, see Starting the Message Broker Profile.
  • Start the ESB Profile. For information on how to start the ESB Profile, see Starting the ESB Profile.

Configuring the JMS publisher

Configure a proxy service named SMSSenderProxy as follows:

Sample proxy service
<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="SMSSenderProxy"
       transports="https,http"
       statistics="disable"
       trace="disable"
       startOnLoad="true">
   <target>
      <inSequence>
         <property name="transport.jms.ContentTypeProperty"
                   value="Content-Type"
                   scope="axis2"/>
      </inSequence>
      <outSequence>
         <property name="TRANSPORT_HEADERS" scope="axis2" action="remove"/>
         <send/>
      </outSequence>
      <endpoint>
         <address uri="jms:/SMSStore?transport.jms.ConnectionFactoryJNDIName=QueueConnectionFactory&amp;java.naming.factory.initial=org.wso2.andes.jndi.PropertiesFileInitialContextFactory&amp;java.naming.provider.url=conf/jndi.properties&amp;transport.jms.DestinationType=queue&amp;transport.jms.ReplyDestination=SMSReceiveNotificationStore"/>
      </endpoint>
   </target>
   <description/>
</proxy>

This proxy service accepts messages sent via the HTTP transport, and stores the messages in the SMSStore queue in the Message Broker Profile of WSO2 EI.

The Property mediator used in this proxy service uses the following properties:

PropertyDescription
TRANSPORT_HEADERS

This property is used in the out sequence to make sure that transport headers (which are JMS headers in this example) are removed from the message when it is passed to the back-end client.

It is recommended to set this property because (according to the JMS specification) a property name can contain any character for which the Character.isJavaIdentifierPart Java method returns 'true'. Therefore when there are headers that contain special characters (e.g accept-encoding), some JMS brokers will give errors.

transport.jms.ContentTypeProperty

The JMS transport uses this property in the above configuration to determine the content type of the response message. If this property is not set, the JMS transport treats the incoming message as plain text.

Note: When this property is used, the content type is determined by the out transport. For example, if the proxy service/API is sending a request, the endpoint reference will determine the content type. Also, if the proxy service/API is sending the response back to the client, the configuration of the service/API will determine the content type.

JMS_WAIT_REPLY

This property can be used to specify how long the system should wait for the JMS queue (SMSRecieveNotification queue) to send the response back. You can add this property to the in sequence as shown below.

<property name="JMS_WAIT_REPLY" value="60000" scope="axis2"/>

The endpoint of this proxy service uses the following properties to map the proxy service with the Message Broker Profile:

PropertyValue for this use caseDescription

address uri

jms:/SMSStore

The destination in which the request received by the proxy service is stored.

java.naming.factory.initial

org.wso2.andes.jndi.PropertiesFileInitialContextFactory

The initial context factory to use.
The value specified here should be the same as that specified in <EI_HOME>/conf/axis2/axis2.xml for the JMS transport receiver.

java.naming.provider.url

conf/jndi.properties

The location of the JNDI service provider.

transport.jms.DestinationType

queueThe destination type of the JMS message that will be generated by the proxy service.
transport.jms.ReplyDestination

SMSReceiveNotificationStore

The destination in which the response generated by the back-end service is stored.

Since this is a two-way invocation, the OUT_ONLY property is not set in the In sequence. 

Configuring the JMS consumer

Configure a proxy service named SMSForwardProxy to consume messages from the SMSStore queue of the Message Broker Profile, and forward the messages to the back-end service.

<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="SMSForwardProxy"
       transports="jms"
       statistics="disable"
       trace="disable"
       startOnLoad="true">
   <target>
      <inSequence>
         <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>text/xml</default>
      </rules>
   </parameter>
   <parameter name="transport.jms.ConnectionFactory">myQueueConnectionFactory</parameter>
   <parameter name="transport.jms.DestinationType">queue</parameter>
   <parameter name="transport.jms.Destination">SMSStore</parameter>
   <description/>
</proxy>

The transport.jms.ConnectionFactory, transport.jms.DestinationType parameter and the transport.jms.Destination properties parameter map the proxy service to the SMSStore queue.

The SimpleStockQuoteService sample shipped with WSO2 EI is used as the back-end service in this example. To invoke this service, the address URI of this proxy service is defined as  http://localhost:9000/services/SimpleStockQuoteService.

Starting the Axis2 server

Follow the steps below to start the Axis2 server:

  1. Open a command prompt (or a shell in Linux) and go to the <EI_HOME>/samples/axis2Server directory.
  2. Execute one of the following commands 
    • On Windowsaxis2server.bat
    • On Linux/Solaris./axis2server.sh

Invoking the JMS publisher

Execute the following command from the <EI_HOME>/samples/axis2Client directory to invoke the SMSSenderProxy proxy service that you defined as the JMS publisher:

ant stockquote -Daddurl=http://localhost:8280/services/SMSSenderProxy -Dsymbol=IBM

Analyzing the output

Analyze the output on the Axis2 server console as well as the output on the client console to understand how a JMS producer can receive a response to a JMS request produced by it.

You will see the following on the Axis2 server console:

Fri Dec 08 11:19:29 IST 2017 samples.services.SimpleStockQuoteService :: Generating quote for : IBM

You will see the following response on the client console:

Standard :: Stock price = $162.04696182786148
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