Implementing JMS with Spring: Messaging Client

Last week, I described how to implement JMS, using a stand-alone client and a Message Driven Bean. In this post and the next, I will describe how to implement JMS using Spring and Message Driven POJOs. This post will describe how to create a Messaging client using Spring. The next post will describe how to implement a Message driven POJO. For this I used a simple servlet that, when invoked will send a text message "hello", to a destination queue. The Message driven pojo, listening on the queue will then receive and print the message. Follow these steps to run the example

1. Setup the JMS environment as described in the "Configuring Weblogic JMS" post
2. Create the Messaging client: This is a simple Java class which uses the spring JmsTemplate to send a message to the queue. The JmsTemplate can be used for message production and synchronous message reception. For asynchronous reception, Spring provides a number of message listener containers that are used to create Message-Driven POJOs (MDPs).

   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. Configure the Bean in the applicationContext.xml file: The following is alisting of the applicationContext.xml file.

   <?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
   The JndiDestinationResolver class can be used to obtain the Queue destinations using the JNDI Name. The send method in JmsTemplate (see QueueSender), uses the JNDI name, which is used by the JndiDestinationResolver to obtain the appropriate destination.
4. Create a servlet to invoke the Message Sender: The following servlet is used to invoke the QueueSender:

   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
5. Update the web.xml file to add the servlet and spring application context:

   <?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>SpringJMSClientWeb</display-name>
   <servlet>
   <description></description>
   <display-name>QueueSenderServlet</display-name>
   <servlet-name>QueueSenderServlet</servlet-name>
   <servlet-class>jms.QueueSenderServlet</servlet-class>
   </servlet>
   <servlet-mapping>
   <servlet-name>QueueSenderServlet</servlet-name>
   <url-pattern>/QueueSenderServlet</url-pattern>
   </servlet-mapping>
   <listener>
   <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
   </listener>
   </web-app>

   web.xml
   The listener defined web.xml (ContextLoaderListener) by default loads the applicationContext.xml file in WEB-INF directory of the web application.

In the next post, we will see how implement the Message Driven POJO to consume the message sent from here.