JMS发布/订阅消息传送例子

2022-10-29 23:03:16

前言

基于上篇文章"基于Tomcat + JNDI + ActiveMQ实现JMS的点对点消息传送"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

    <Resource name="topic/connectionFactory" auth="Container"

        type="org.apache.activemq.ActiveMQConnectionFactory" description="JMS Connection Factory"

        factory="org.apache.activemq.jndi.JNDIReferenceFactory"

        brokerURL="failover:(tcp://localhost:61616)?initialReconnectDelay=100&amp;maxReconnectAttempts=5"

        brokerName="LocalActiveMQBroker" useEmbeddedBroker="false" />

    <Resource name="topic/topic0"

        auth="Container"

        type="org.apache.activemq.command.ActiveMQTopic" description="My Topic" factory="org.apache.activemq.jndi.JNDIReferenceFactory"

        physicalName="TestTopic" />

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。

参考资料

http://howtodoinjava.com/jms/jms-publish-subscribe-message-example/

码农公寓

前言

在Tomcat中配置JNDI

在Web工厂中编写代码

参考资料

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