# SEND a message to a TOPIC

Paul Tomoiu

●

JMS,

WebLogic,

Oracle,

Topics,

Messaging,

Examples

●

Published 2022-12-03

This tutorial explains to you how we can write (send) a simple message to a topic with Java EE. For testing the code I used a WebLogic Application Server.

# JMS Topic

A JMS topic is the channel through which users subscribe to receive specific messages from a producer in the publish-and-subscribe model of JMS messaging. The model can be compared to subscribing to a newspaper. In my case I used a WebLogic Topic. Here is a picture showing the Topic without any message received/ published:

After the messages are sent/ published (using the Java code in my case), you can see some messages on the queue:

You can see that there is no "Current" messages. It is because there is no durable subscriber.

# How to publish/send a message to a WebLogic Topic using Java

For testing, I used the following: Eclipse, JDK 8, a WebLogic Server 12c, and I created a Web application using JSF (PrimeFaces).

On a JSF page (.xhtml) I put a button to send the message:

<html>
  <body>
     <h:form>
        <p:commandbutton value="Publish Message" actionlistener="#{sendMessageTopic.sendMessage}">  </p:commandbutton>
     </h:form>
  </body>
</html>

Here is the SendMessageTopic.java file :

SendMessageTopic.java
package com;
import java.util.Hashtable;
 
//import javax.faces.application.FacesMessage;
import javax.faces.bean.ManagedBean;
//import javax.faces.context.FacesContext;
import javax.faces.event.ActionEvent;
 
import javax.naming.*;  
import javax.jms.*; 
 
@ManagedBean (name = "sendMessageTopic")
public class SendMessageTopic {
 
   // Defines the JNDI context factory.
   public final static String JNDI_FACTORY="weblogic.jndi.WLInitialContextFactory";
 
   // Defines the JMS context factory.
   public final static String JMS_FACTORY="ConnectionFactory2";
 
   // Defines the topic.
   public final static String MyTOPIC="jndi/Topic1";
          
   // Defines the WebLogic URL. The port is for the Managed Server or
   // the Admin Server where the JMS Server is running.
   public final static String WebLogicURL="t3://pc:7004";   
   
   public void sendMessage() throws Exception {
         
       //Create and start connection 
       Hashtable env = new Hashtable();
       env.put(Context.INITIAL_CONTEXT_FACTORY, JNDI_FACTORY);
       env.put(Context.PROVIDER_URL, WebLogicURL);
        
       InitialContext ic=new InitialContext(env);   
        
       TopicConnectionFactory f=(TopicConnectionFactory)ic.lookup("ConnectionFactory2") ;   
        
       TopicConnection con=f.createTopicConnection();  
       con.start();  
        
       //2) create topic session  
       TopicSession ses = con.createTopicSession(false, Session.AUTO_ACKNOWLEDGE);  
        
       //3) get the Topic object  
       Topic topic = (Topic)ic.lookup("jndi/Topic1");  
        
       //4)create topic publisher          
       TopicPublisher topicPublisher = ses.createPublisher(topic);  
       topicPublisher.setDeliveryMode(DeliveryMode.NON_PERSISTENT);
        
       //5) create TextMessage object  
        TextMessage msg=ses.createTextMessage();  
        msg.setText("This is my message !");
         
       //7) send message  
        topicPublisher.publish(msg);  
        
       System.out.println("Message successfully published: " + msg);  
 
       //8) connection close 
       con.close();
   }
}