阅读目录

前言

基于上篇文章""很容易就可以编写一个发布/订阅消息传送例子，相关环境准备与该篇文章基本类似，主要的区别如下。

在Tomcat中配置JNDI

配置连接工厂和话题

在Web工厂中编写代码

新建一个发布者Servlet

package pubSub;import java.io.IOException;import java.io.PrintWriter;import javax.naming.InitialContext;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.jms.Topic;import javax.jms.Session;import javax.jms.TextMessage;import javax.jms.TopicPublisher;import javax.jms.DeliveryMode;import javax.jms.TopicSession;import javax.jms.TopicConnection;import javax.jms.TopicConnectionFactory;/** * Servlet implementation class JMSTest */@WebServlet("/Publish")public class Publisher extends HttpServlet {    private static final long serialVersionUID = 1L;    /**     * @see HttpServlet#HttpServlet()     */    public Publisher() {        super();        // TODO Auto-generated constructor stub    }    /**     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse     *      response)     */    protected void doGet(HttpServletRequest request,            HttpServletResponse response) throws ServletException, IOException {        PrintWriter out = response.getWriter();        try {            // get the initial context            InitialContext ctx = new InitialContext();            // lookup the topic object            Topic topic = (Topic) ctx.lookup("java:comp/env/topic/topic0");            // lookup the topic connection factory            TopicConnectionFactory connFactory = (TopicConnectionFactory) ctx                    .lookup("java:comp/env/topic/connectionFactory");            // create a topic connection            TopicConnection topicConn = connFactory.createTopicConnection();            // create a topic session            TopicSession topicSession = topicConn.createTopicSession(false,                    Session.AUTO_ACKNOWLEDGE);            // create a topic publisher            TopicPublisher topicPublisher = topicSession.createPublisher(topic);            topicPublisher.setDeliveryMode(DeliveryMode.NON_PERSISTENT);            // create the "Hello World" message            TextMessage message = topicSession.createTextMessage();            message.setText("Hello World");            // publish the messages            topicPublisher.publish(message);            // print what we did            out.write("Message published: " + message.getText());            // close the topic connection            topicConn.close();        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    /**     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse     *      response)     */    protected void doPost(HttpServletRequest request,            HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub    }}

新建一个订阅者Servlet

package pubSub;import java.io.IOException;import java.io.PrintWriter;import javax.jms.Session;import javax.jms.TextMessage;import javax.jms.Topic;import javax.jms.TopicConnection;import javax.jms.TopicConnectionFactory;import javax.jms.TopicSession;import javax.jms.TopicSubscriber;import javax.naming.InitialContext;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class Receive */@WebServlet("/Subscribe")public class Subscriber extends HttpServlet {    private static final long serialVersionUID = 1L;    /**     * @see HttpServlet#HttpServlet()     */    public Subscriber() {        super();        // TODO Auto-generated constructor stub    }    /**     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse     *      response)     */    protected void doGet(HttpServletRequest request,            HttpServletResponse response) throws ServletException, IOException {        PrintWriter out = response.getWriter();        try {            // get the initial context            InitialContext ctx = new InitialContext();            // lookup the topic object            Topic topic = (Topic) ctx.lookup("java:comp/env/topic/topic0");            // lookup the topic connection factory            TopicConnectionFactory connFactory = (TopicConnectionFactory) ctx                    .lookup("java:comp/env/topic/connectionFactory");            // create a topic connection            TopicConnection topicConn = connFactory.createTopicConnection();            // create a topic session            TopicSession topicSession = topicConn.createTopicSession(false,                    Session.AUTO_ACKNOWLEDGE);            // create a topic subscriber            TopicSubscriber topicSubscriber = topicSession                    .createSubscriber(topic);            // start the connection            topicConn.start();            // receive the message            TextMessage message = (TextMessage) topicSubscriber.receive();            // print the message            out.write("Message received: " + message.getText());            // close the topic connection            topicConn.close();        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }    /**     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse     *      response)     */    protected void doPost(HttpServletRequest request,            HttpServletResponse response) throws ServletException, IOException {        // TODO Auto-generated method stub    }}

运行Web工程，分别打开多个标签访问订阅servlet，然后访问发布servlet，结果如下：

在订阅者订阅消息的时候，一开始没接收到消息，一旦发布者发布消息后，订阅者马上收到消息。