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：
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，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，同时我们可以打开页面，发现刚才的消息已经不见了，如下图所示
