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/