深入掌握JMS（五）实战Topic

最新推荐文章于 2018-12-01 18:19:00 发布

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#JMS #ActiveMQ #Apache

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本文通过示例介绍了Java消息服务（JMS）中主题（Topic）的发布/订阅模型。该模型允许多个消费者同时监听同一主题，并确保每个发布的消息都能被所有订阅者接收。示例使用了Apache ActiveMQ作为消息中间件。

与Queue不同的是，Topic实现的是发布/订阅模型，在下面的例子中，启动2个消费者共同监听一个Topic，然后循环给这个Topic中发送多个消息。

import javax.jms.Connection;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageConsumer;
import javax.jms.MessageListener;
import javax.jms.MessageProducer;
import javax.jms.Session;
import javax.jms.TextMessage;
import javax.jms.Topic;

import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.activemq.command.ActiveMQTopic;

public class TopicTest {

    public static void main(String[] args) throws Exception {
        ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("vm://localhost");

        Connection connection = factory.createConnection();
        connection.start();

        //创建一个Topic
        Topic topic= new ActiveMQTopic("testTopic");
        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);

        //注册消费者1
        MessageConsumer comsumer1 = session.createConsumer(topic);
        comsumer1.setMessageListener(new MessageListener(){
            public void onMessage(Message m) {
                try {
                    System.out.println("Consumer1 get " + ((TextMessage)m).getText());
                } catch (JMSException e) {
                    e.printStackTrace();
                }
            }
        });

        //注册消费者2
        MessageConsumer comsumer2 = session.createConsumer(topic);
        comsumer2.setMessageListener(new MessageListener(){
            public void onMessage(Message m) {
                try {
                    System.out.println("Consumer2 get " + ((TextMessage)m).getText());
                } catch (JMSException e) {
                    e.printStackTrace();
                }
            }

        });

        //创建一个生产者，然后发送多个消息。
        MessageProducer producer = session.createProducer(topic);
        for(int i=0; i<10; i++){
            producer.send(session.createTextMessage("Message:" + i));
        }
    }

}

运行后得到下面的输出结果：

Consumer1 get Message:0
Consumer2 get Message:0
Consumer1 get Message:1
Consumer2 get Message:1
Consumer1 get Message:2
Consumer2 get Message:2
Consumer1 get Message:3
Consumer2 get Message:3
Consumer1 get Message:4
Consumer2 get Message:4
Consumer1 get Message:5
Consumer2 get Message:5
Consumer1 get Message:6
Consumer2 get Message:6
Consumer1 get Message:7
Consumer2 get Message:7
Consumer1 get Message:8
Consumer2 get Message:8
Consumer1 get Message:9
Consumer2 get Message:9

说明每一个消息都会被所有的消费者消费。