主动在ActiveMQ上消耗消息

Question

I have used the following java application to put a message on a JMS queue

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


public class Main {
public static void main(String[] args) {
    ApplicationContext ctx = new ClassPathXmlApplicationContext("app-context.xml");
    JmsMessageSender jmsMessageSender = (JmsMessageSender)ctx.getBean("jmsMessageSender");

    java.lang.String text = "{\"name\": \"Bob\"}";
    jmsMessageSender.send(text);
    ((ClassPathXmlApplicationContext)ctx).close();
}

}

The message sender looks like this:

import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.Message;
import javax.jms.Session;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jms.core.JmsTemplate;
import org.springframework.jms.core.MessageCreator;
import org.springframework.stereotype.Service;

@Service
public class JmsMessageSender {
@Autowired
private JmsTemplate jmsTemplate;
public void send(final String text) {
    this.jmsTemplate.send(new MessageCreator() {
        @Override
        public Message createMessage(Session session) throws JMSException {
            Message message = session.createTextMessage(text);
            return message;
        }
    });
}


}

And the spring config is as follows:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xmlns:beans="http://www.springframework.org/schema/beans"
   xmlns:context="http://www.springframework.org/schema/context"
   xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">


<context:component-scan base-package="com.intonilof" />
<bean id="amqConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">
    <constructor-arg index="0" value="tcp://127.0.0.1:61616" />
</bean>

<bean id="connectionFactory"
      class="org.springframework.jms.connection.CachingConnectionFactory">
    <constructor-arg ref="amqConnectionFactory" />
</bean>

<bean id="defaultDestination" class="org.apache.activemq.command.ActiveMQTopic">
    <constructor-arg index="0" value="emailsToSend" />
</bean>

<bean id="jmsTemplate" class="org.springframework.jms.core.JmsTemplate">
    <property name="connectionFactory" ref="connectionFactory" />
    <property name="defaultDestination" ref="defaultDestination" />
</bean>

If I use this code to put the message on how can I create a consumer for the topic which will come and consume the jms message at a later time?

I have tried the following but it is not consuming the message:

import org.apache.activemq.command.ActiveMQTextMessage;
import org.apache.log4j.Logger;
import org.json.JSONObject;

import java.util.Date;

public class App {
final static Logger logger = Logger.getLogger(App.class);
public static void main(String[] args) throws Exception {
    thread(new HelloWorldConsumer(), false);
}

public static void thread(Runnable runnable, boolean daemon) {
    Thread brokerThread = new Thread(runnable);
    brokerThread.setDaemon(daemon);
    brokerThread.start();
}

public static class HelloWorldConsumer implements Runnable, ExceptionListener {

    public void run() {
        try {
            logger.trace("Running at: " + new Date().toString());
            ActiveMQConnectionFactory connectionFactory = new ActiveMQConnectionFactory("tcp://localhost:61616");
            Connection connection = connectionFactory.createConnection();
            connection.start();
            connection.setExceptionListener(this);
            Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
            Queue queue = session.createQueue("emailsToSend?consumer.retroactive=true");
            MessageConsumer consumer = session.createConsumer(topic);
            Message message = consumer.receive(1000);

            if (message instanceof TextMessage) {
                    System.out.println("Found message");

            } else if (message == null){
                logger.trace("No messages");
            }
            consumer.close();
            session.close();
            connection.close();
        } catch (Exception e) {
            logger.info("Caught: " + e);
            e.printStackTrace();
        }
    }

    public synchronized void onException(JMSException ex) {
        logger.trace("JMS Exception occured.  Shutting down client.");
    }
}
}

Answer 1

You need to create durable topic subscription first. Then JMS will retain all published messages while the subscriber is disconnected and deliver them when it reconnects.