基于Tomcat + JNDI + ActiveMQ实现JMS的点对点消息传送

前言

　　写了一个简单的JMS例子，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...)。

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。

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" /> 

启动ActiveMQ

　　CMD到ActiveMQ安装路径下的bin目录，输入“activemq start”指令即可启动，可在浏览器中输入地址http://localhost:8161/admin，查看队列、话题等信息。

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
    }

}

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

参考资料

http://howtodoinjava.com/jms/jms-point-to-point-message-example/