使用Tomcat、JNDI与ActiveMQ实现JMS消息通信服务

前言

之所以使用JNDI 是出于通用性考虑，该例子使用JMS规范提供的通用接口，没有使用具体JMS提供者的接口，这样可以保证我们编写的程序适用于任何一种JMS实现(ActiveMQ、HornetQ等)。

什么是JNDI：JNDI(Java Naming and Directory Interface)是一个标准规范，类似于JDBC，JMS等规范，为开发人员提供了查找和访问各种命名和目录服务的通用、统一的接口。J2EE 规范要求所有 J2EE 容器都要提供 JNDI 规范的实现，因此Tomcat就实现了JNDI 规范。

PTP(Point to point)消息模式（JMS的点对点消息传送）

1、使用Tomcat配置JNDI

找到Tomcat安装路径下的conf文件夹，打开context.xml，添加如下配置：

<Resource name="queue/connectionFactory"
                auth="Container"
                type="org.apache.activemq.ActiveMQConnectionFactory"
                description="JMS Connection Factory"
                factory="org.apache.activemq.jndi.JNDIReferenceFactory"
                brokerURL="tcp://localhost:61616"
                brokerName="LocalActiveMQBroker" />  

<Resource name="queue/queue0"
                auth="Container"
                type="org.apache.activemq.command.ActiveMQQueue"
                description="My Queue"
                factory="org.apache.activemq.jndi.JNDIReferenceFactory"
                physicalName="TomcatQueue" />

2、启动ActiveMQ

3、编写一个Web工程

Eclipse上新建web工程，添加ActiveMQ依赖的jar包，然后开始编写两个Servlet，一个用于生产消息，另一个用于消费消息，如下代码：

消息生产者Servlet：

import java.io.IOException;
import java.io.PrintWriter;

import javax.jms.DeliveryMode;
import javax.jms.Queue;
import javax.jms.QueueConnection;
import javax.jms.QueueConnectionFactory;
import javax.jms.QueueSender;
import javax.jms.QueueSession;
import javax.jms.Session;
import javax.jms.TextMessage;
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 JMSTest
 */
@WebServlet("/Send")
public class Send extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public Send() {
        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 context = new InitialContext();

            // lookup the queue object
            Queue queue = (Queue) context.lookup("java:comp/env/queue/queue0");

            // lookup the queue connection factory
            QueueConnectionFactory conFactory = (QueueConnectionFactory) context
                    .lookup("java:comp/env/queue/connectionFactory");

            // create a queue connection
            QueueConnection queConn = conFactory.createQueueConnection();

            // create a queue session
            QueueSession queSession = queConn.createQueueSession(false,
                    Session.DUPS_OK_ACKNOWLEDGE);

            // create a queue sender
            QueueSender queSender = queSession.createSender(queue);
            queSender.setDeliveryMode(DeliveryMode.NON_PERSISTENT);

            // create a simple message to say "Hello World"
            TextMessage message = queSession.createTextMessage("Hello World");

            // send the message
            queSender.send(message);

            // print what we did
            out.write("Message Sent: " + message.getText());

            // close the queue connection
            queConn.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
    }

}

消息消费者Servlet：

import java.io.IOException;
import java.io.PrintWriter;

import javax.jms.Queue;
import javax.jms.QueueConnection;
import javax.jms.QueueConnectionFactory;
import javax.jms.QueueReceiver;
import javax.jms.QueueSession;
import javax.jms.Session;
import javax.jms.TextMessage;
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("/Receive")
public class Receive extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public Receive() {
        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 context = new InitialContext();

            // lookup the queue object
            Queue queue = (Queue) context.lookup("java:comp/env/queue/queue0");

            // lookup the queue connection factory
            QueueConnectionFactory conFactory = (QueueConnectionFactory) context
                    .lookup("java:comp/env/queue/connectionFactory");

            // create a queue connection
            QueueConnection queConn = conFactory.createQueueConnection();

            // create a queue session
            QueueSession queSession = queConn.createQueueSession(false,
                    Session.AUTO_ACKNOWLEDGE);

            // create a queue receiver
            QueueReceiver queReceiver = queSession.createReceiver(queue);

            // start the connection
            queConn.start();

            // receive a message
            TextMessage message = (TextMessage) queReceiver.receive();

            // print the message
            out.write("Message Received: " + message.getText());

            // close the queue connection
            queConn.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
    }

}

4、验证结果

在Tomcat里运行该Web工程，执行消息生产者Servlet，返回消息发送成功标志，同时我们可以在http://localhost:8161/admin/queues.jsp查看到该消息，如下图所示

继续执行消息消费者Servlet，返回消息接收成功标志，同时我们可以打开http://localhost:8161/admin/queues.jsp页面，发现刚才的消息已经不见了，如下图所示

Pub/Sub消息模式（JMS发布/订阅消息传送）

1、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" />

2、启动ActiveMQ

3、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
    }

}

4、验证结果

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。