java - 无法使用activemq获取异步消息

Question

大家好，我无法使用 Activity mq 接收异步消息，下面的代码是我用于发布消息并订阅它的代码。

    public class publishMessage extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

       InitialContext initCtx = new InitialContext();
            Context envContext = (Context) initCtx.lookup("java:comp/env");
            ActiveMQConnectionFactory connectionFactory = (ActiveMQConnectionFactory) envContext.lookup("jms/ConnectionFactory");
            Connection connection = connectionFactory.createConnection();
            connection.start() ;
            Session session = connection.createSession(true, Session.AUTO_ACKNOWLEDGE);
            Destination destination = session.createQueue("jms/topic/MyQueue");
            MessageProducer producer = session.createProducer(destination);
            producer.setDeliveryMode(DeliveryMode.PERSISTENT) ;
            TextMessage msg=session.createTextMessage();
            msg.setText("Message sent");
                    System.out.println("Message Sent");
            producer.send(msg);
            session.commit() ;
            connection.close() ;
            }catch(Exception ex){
                ex.printStackTrace() ;
            }
    }}


class Consumer{

    protected Queue queue;


    protected String queueName = "jms/topic/MyQueue";

    protected String url = ActiveMQConnection.DEFAULT_BROKER_URL;

    protected int ackMode = Session.AUTO_ACKNOWLEDGE;

    public static void main(String[] args) {
        Consumer rec=new Consumer();
        try {
            rec.run();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    public void run() throws JMSException{

        System.out.println("URL:" + url);
        ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory(url);
        TopicConnection connection = (TopicConnection)connectionFactory.createTopicConnection();
        connection.setClientID("Testingconn1") ;
        connection.start();
        MessageConsumer consumer = null;
        Session session = connection.createSession(true, Session.CLIENT_ACKNOWLEDGE);
        queue = session.createQueue(queueName) ;
        consumer = session.createConsumer(queue);
        consumer.setMessageListener(new MyListener()) ;
        session.commit() ;
        consumer.close();
        session.close();
        connection.close();
    }

}

package com.java;

import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.MessageListener;
import javax.jms.TextMessage;

public class MyListener implements MessageListener{

    @Override
    public void onMessage( final Message message )
    {
        if ( message instanceof TextMessage )
        {
            final TextMessage textMessage = (TextMessage) message;
            try
            {
                System.out.println("Listener:" +  textMessage.getText() );
            }
            catch (final JMSException e)
            {
                e.printStackTrace();
            }
        }

    }
}

当我执行上述代码时，发布者成功发送一条消息，并且当我启动消费者时，输出按要求出现，没有输出进入我的控制台。

请帮助我解决它或建议一个代码来接收异步消息。

Answer 1

您的消费者代码实际上并没有给消费者任何时间来消费消息。当消费者将存活一段时间并且您的应用程序可以处理传入消息时，将使用异步消费者。在上面的代码中，您最好使用 MessageConsumer 的定时接收方法，例如Consumer.receive(5000) 或一些适合您应用程序的时间段。不能保证您的消费者在创建后立即收到消息，因为代理需要时间来注册消费者并将消息路由到它，因此您必须在您的应用程序中允许这一点。