Making Simple POJO to Message Driven POJO with Spring

In the past, I posted a few examples of implementing Messaging using J2EE and Spring. This post will describe how to use the Spring MessageListenerAdapter to enable any Java class to act as a Message Driven POJO. This can be used to enable existing applications to use Asynchronous Messaging. Follow these steps to run the example:

The Message Driven POJO

1. The following is the code for the Simple Java class that will be used as a Message Driven POJO

   public class MsgListener {
   public void receive(String message) {
     System.out.println("The message was : " + message);
   }
   }

   MsgListener.java
2. The Spring Configuration used for this is shown below

   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"
   "http://www.springframework.org/dtd/spring-beans.dtd">
   <beans>
    <bean id="messageListener" class="org.springframework.jms.listener.adapter.MessageListenerAdapter">
      <constructor-arg>
        <bean class="jms.MsgListener" />
      </constructor-arg>
      <property name="defaultListenerMethod" value="receive" />
      <!-- we don't want automatic message context extraction -->
      <property name="messageConverter">
        <bean class="org.springframework.jms.support.converter.SimpleMessageConverter"></bean>
      </property>
    </bean>
   
   <!-- and this is the message listener container... -->
   <bean id="listenerContainer" class="org.springframework.jms.listener.DefaultMessageListenerContainer">
     <property name="concurrentConsumers" value="5" />
     <property name="connectionFactory" ref="connectionFactory" />
     <property name="destination" ref="queue" />
     <property name="messageListener" ref="messageListener" />
   </bean>
   
   <bean id="jndiTemplate" class="org.springframework.jndi.JndiTemplate">
     <property name="environment">
       <props>
         <prop key="java.naming.factory.initial">weblogic.jndi.WLInitialContextFactory</prop>
         <prop key="java.naming.provider.url">t3://localhost:20001</prop>
       </props>
     </property>
   </bean>
   <bean id="connectionFactory" class="org.springframework.jndi.JndiObjectFactoryBean">
     <property name="jndiTemplate">
       <ref bean="jndiTemplate" />
     </property>
     <property name="jndiName">
       <value>jms/connectionFactory</value>
     </property>
   </bean>
   
   <bean id="queue" class="org.springframework.jndi.JndiObjectFactoryBean">
     <property name="jndiTemplate">
       <ref bean="jndiTemplate" />
     </property>
     <property name="jndiName">
       <value>jms/testQueue</value>
     </property>
   </bean>
   </beans>

   WEB-INF/applicationContext.xml
   Note: The MessageListenerAdapter used here (bean-messageListener) is acts as an adapter to enable the MsgListener class to receive messages.
3. The Web Deployment descriptor

   <?xml version="1.0" encoding="UTF-8"?>
   <web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
   <display-name>SpringJMSWeb</display-name>
   <welcome-file-list>
     <welcome-file>index.html</welcome-file>
     <welcome-file>index.htm</welcome-file>
     <welcome-file>index.jsp</welcome-file>
   </welcome-file-list>
    <listener>
      <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
   </web-app>

   web.xml

The Client

1. Create a Simple Servlet that will be used to start the application. The code for the Servlet is shown below.

   public class QueueSenderServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet {
   protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
     WebApplicationContext ctx = WebApplicationContextUtils.getRequiredWebApplicationContext(this.getServletContext());
     QueueSender sender = (QueueSender)ctx.getBean("jmsSender");
     sender.sendMesage();
   } 
   }

   QueueSenderServlet.java
2. The following code shows Queue Sender. The Queue sender uses the JMSTemplate to send message to the queue.

   public class QueueSender {
   private JmsTemplate jmsTemplate;
   public void setJmsTemplate(JmsTemplate jmsTemplate) {
     this.jmsTemplate = jmsTemplate;
   }
   public void sendMesage() {
     jmsTemplate.send("jms/testQueue", new MessageCreator() {
       public Message createMessage(Session session) throws JMSException {
         return session.createTextMessage("Hello");
       }
     });
   }
   }

   QueueSender.java
3. Spring Configuration: The Spring configuration file is shown below

   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"
   "http://www.springframework.org/dtd/spring-beans.dtd">
   <beans>
   <bean id="jndiTemplate" class="org.springframework.jndi.JndiTemplate">
     <property name="environment">
       <props>
         <prop key="java.naming.factory.initial">weblogic.jndi.WLInitialContextFactory</prop>
         <prop key="java.naming.provider.url">t3://localhost:20001</prop>
       </props>
     </property>
   </bean>
   
   <bean id="queueConnectionFactory" class="org.springframework.jndi.JndiObjectFactoryBean">
     <property name="jndiTemplate">
       <ref bean="jndiTemplate" />
     </property>
     <property name="jndiName">
       <value>jms/connectionFactory</value>
     </property>
   </bean>
   
   <bean id="jmsDestinationResolver" class="org.springframework.jms.support.destination.JndiDestinationResolver">
     <property name="jndiTemplate">
       <ref bean="jndiTemplate" />
     </property>
     <property name="cache">
       <value>true</value>
     </property>
   </bean>
   
   <bean id="queueTemplate" class="org.springframework.jms.core.JmsTemplate">
     <property name="connectionFactory">
       <ref bean="queueConnectionFactory" />
     </property>
     <property name="destinationResolver">
       <ref bean="jmsDestinationResolver" />
     </property>
   </bean>
   
   <bean id="jmsSender" class="jms.QueueSender">
     <property name="jmsTemplate">
       <ref bean="queueTemplate" />
     </property>
   
   </bean>
   </beans>

   WEB-INF/applicationContext.xml
4. The Web Deployment descriptor

   <?xml version="1.0" encoding="UTF-8"?>
   <web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
   <display-name>SpringJMSWeb</display-name>
   <welcome-file-list>
     <welcome-file>index.html</welcome-file>
     <welcome-file>index.htm</welcome-file>
     <welcome-file>index.jsp</welcome-file>
   </welcome-file-list>
   <listener>
     <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
   </listener>
   </web-app>

   web.xml