java - ACTIVEMQ-发布者订阅者 Hello World 示例

Question

有两个程序:订阅者和发布者...订阅者能够将消息放到主题上并且消息发送成功。当我在浏览器上检查 activemq 服务器时，它显示 1 msg enqueued 。但是当我运行消费者代码时，它没有收到消息

这里是生产者代码:

import javax.jms.*;

import org.apache.activemq.ActiveMQConnection;
import org.apache.activemq.ActiveMQConnectionFactory;

public class producer {

    private static String url = ActiveMQConnection.DEFAULT_BROKER_URL;

    public static void main(String[] args) throws JMSException {

        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(url);
        Connection connection = connectionFactory.createConnection();
        connection.start();

        // JMS messages are sent and received using a Session. We will
        // create here a non-transactional session object. If you want
        // to use transactions you should set the first parameter to 'true'
        Session session = connection.createSession(false,
                Session.AUTO_ACKNOWLEDGE);

        Topic topic = session.createTopic("testt");

        MessageProducer producer = session.createProducer(topic);

        // We will send a small text message saying 'Hello'

        TextMessage message = session.createTextMessage();

        message.setText("HELLO JMS WORLD");
        // Here we are sending the message!
        producer.send(message);
        System.out.println("Sent message '" + message.getText() + "'");

        connection.close();
    }
}

运行此代码后，控制台的输出为:

26 Jan, 2012 2:30:04 PM org.apache.activemq.transport.failover.FailoverTransport doReconnect
INFO: Successfully connected to tcp://localhost:61616
Sent message 'HELLO JMS WORLD'

这里是消费者代码:

import javax.jms.*;

import org.apache.activemq.ActiveMQConnection;
import org.apache.activemq.ActiveMQConnectionFactory;

public class consumer {
    // URL of the JMS server
    private static String url = ActiveMQConnection.DEFAULT_BROKER_URL;

    // Name of the topic from which we will receive messages from = " testt"

    public static void main(String[] args) throws JMSException {
        // Getting JMS connection from the server

        ConnectionFactory connectionFactory = new ActiveMQConnectionFactory(url);
        Connection connection = connectionFactory.createConnection();
        connection.start();

        Session session = connection.createSession(false,
                Session.AUTO_ACKNOWLEDGE);

        Topic topic = session.createTopic("testt");

        MessageConsumer consumer = session.createConsumer(topic);

        MessageListener listner = new MessageListener() {
            public void onMessage(Message message) {
                try {
                    if (message instanceof TextMessage) {
                        TextMessage textMessage = (TextMessage) message;
                        System.out.println("Received message"
                                + textMessage.getText() + "'");
                    }
                } catch (JMSException e) {
                    System.out.println("Caught:" + e);
                    e.printStackTrace();
                }
            }
        };

        consumer.setMessageListener(listner);
        connection.close();

    }
}    

运行此代码后，它不显示任何内容。有人可以帮我解决这个问题吗？

Answer 1

您的问题是您的消费者正在运行，然后立即关闭。

尝试将其添加到您的消费者中:

    consumer.setMessageListener(listner);

    try {
        System.in.read();
    } catch (IOException e) {
        e.printStackTrace();
    }

    connection.close();

这将等到您按下一个键才停止。

其他需要考虑的事项:

• 使用 finally block 结束
• Java 命名约定鼓励类的首字母使用大写