基於上篇文章"基於Tomcat + JNDI + ActiveMQ實現JMS的點對點消息傳送"很容易就可以編寫一個發佈/訂閱消息傳送例子,相關環境準備與該篇文章基本類似,主要的區別如下。 在Tomcat中配置JNDI 配置連接工廠和話題 在Web工廠中編寫代碼 新建一個發佈者Servlet 新建一個 ...
基於上篇文章"基於Tomcat + JNDI + ActiveMQ實現JMS的點對點消息傳送"很容易就可以編寫一個發佈/訂閱消息傳送例子,相關環境準備與該篇文章基本類似,主要的區別如下。
在Tomcat中配置JNDI
配置連接工廠和話題
<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&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工廠中編寫代碼
新建一個發佈者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 } }
新建一個訂閱者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 } }
運行Web工程,分別打開多個標簽訪問訂閱servlet,然後訪問發佈servlet,結果如下:
在訂閱者訂閱消息的時候,一開始沒接收到消息,一旦發佈者發佈消息後,訂閱者馬上收到消息。
代碼參考自:http://howtodoinjava.com/jms/jms-publish-subscribe-message-example/