topichellobean.java

《J2EE企业级应用开发》一书的配套源代码

package com.hellking.study.ejb;
import java.rmi.RemoteException;

import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
import javax.ejb.EJBException;

import javax.naming.InitialContext;
import javax.naming.Context;

import javax.jms.TopicConnectionFactory;
import javax.jms.TopicConnection;
import javax.jms.TopicSession;
import javax.jms.TopicPublisher;
import javax.jms.Topic;
import javax.jms.Session;
import javax.jms.TextMessage;
import javax.jms.JMSException;



/**
 * Hello bean, send a message to the configured topic.
 * The JMS stuff is configured via the deployment descriptor.
 *
 * The TopicConnection is comparable to the JDBC DataSource,
 * and the TopicSession to the JDBC Connection.
 *
 * @author Peter Antman
 * @version $Revision: 3.1 $
 */
public class TopicHelloBean implements SessionBean {

  /**
   * Name used to lookup TopicConnectionFactory
   */
  private static final String CONNECTION_JNDI =
    "java:comp/env/jms/HellkingTopicConnection";

  /**
   * Name used to lookup topic destination
   */
  private static final String TOPIC_JNDI = "java:comp/env/jms/HellkingTopicName";

  private SessionContext ctx = null;

  private Topic topic = null;
  private TopicConnection topicConnection = null;

  public TopicHelloBean() {
  }

  public void setSessionContext(SessionContext ctx) {

    this.ctx = ctx;

  }

  public void ejbCreate()  {

    try {

      Context context = new InitialContext();

      // Lookup the topic
      topic = (Topic)context.lookup(TOPIC_JNDI);

      // Lookup the connection factory
      TopicConnectionFactory factory =
        (TopicConnectionFactory)context.lookup(CONNECTION_JNDI);

      topicConnection = factory.createTopicConnection();

      // Keep both around

    } catch (Exception ex) {

      // JMSException or NamingException could be thrown
      ex.printStackTrace();
      throw new EJBException(ex.toString());

    }
  }

  /**
   * Send a message with a message nr in property MESSAGE_NR
   */
  public void hello(String msg) {

    sendMessage(msg);

  }

  public void ejbRemove() throws RemoteException {

    if (topicConnection != null) {

      try {

        // Remember to close the connection when the bean is destroyed
        topicConnection.close();

      } catch (Exception e) {

        e.printStackTrace();

      }

    }

  }

  public void ejbActivate() {}
  public void ejbPassivate() {}

  /**
   * Help method to send message via JMS
   */
  private void sendMessage(String msg) {

    TopicSession topicSession = null;

    try {

      TopicPublisher topicPublisher = null;
      TextMessage message = null;

      // Create a session
      topicSession = topicConnection.createTopicSession(true,
        Session.AUTO_ACKNOWLEDGE);

      // Create a publisher
      topicPublisher = topicSession.createPublisher(topic);

      // Create a message
      message = topicSession.createTextMessage();
      message.setText(msg);

      // Publish it
      System.out.println("Publishing message " + msg);
      topicPublisher.publish(message);

    } catch (JMSException ex) {

      ex.printStackTrace();
      ctx.setRollbackOnly();
      throw new EJBException(ex.toString());

    } finally {

      // ALWAYS close the session. It's pooled, so do not worry.

      if (topicSession != null) {

         try {

           topicSession.close();

         } catch (Exception e) {

           e.printStackTrace();

         }

       }

     }

  }

}