ActiveMQ消息中间件

对于这次ActiveMQ的学习，故做一次学习记录，面试的时候能翻翻看看。
先导入pom.xml

 <dependency>
            <groupId>org.apache.activemq</groupId>
            <artifactId>activemq-all</artifactId>
            <version>5.15.9</version>
</dependency>

生产者代码

 		ActiveMQConnectionFactory activeMQConnectionFactory = new ActiveMQConnectionFactory("tcp://localhost:61616");
        Connection connection = activeMQConnectionFactory.createConnection();
        connection.start();
        Session session = connection.createSession(true, Session.AUTO_ACKNOWLEDGE);
        Queue queue = session.createQueue("message_queue");
        javax.jms.MessageProducer producer = session.createProducer(queue);


        for(int i=0;i<10;i++){
            producer.send(session.createTextMessage("消息队列【"+i+"】"));
        }
        session.commit();
        connection.close();

消费者代码

		ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("tcp://localhost:61616");
        Connection connection = factory.createConnection();
        connection.start();
		// 第一个参数代表是否开启事务，第二个参数代表传递参数
        Session session = connection.createSession(true, Session.AUTO_ACKNOWLEDGE);
        Queue message_queue = session.createQueue("message_queue");
        MessageConsumer consumer = session.createConsumer(message_queue);
        consumer.setMessageListener(new MessageListener() {

            public void onMessage(Message message) {
                try {
                    TextMessage textMessage = (TextMessage) message;
                    System.err.println("通道1："+textMessage.getText());
                } catch (Exception e) {
                    e.printStackTrace();
                }


            }
        });

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那些情况会引起消息重发？

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1.消费端开启事务，调用了 session.rollback();
2:消费端开启事务，没有调用session.commit();
3:消费的使用Session.CLIENT_ACKNOWLEDGE传递模式，调用session.recover();

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消息重发时间间隔和重发次数

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默认时间间隔：1000ms
默认重发次数：6
消费者可以自定义重发策略，次数达到后，将进入ActiveMQ.DLQ（死信队列）

		ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory("tcp://localhost:61616");

        RedeliveryPolicy redeliveryPolicy = new RedeliveryPolicy();
        // 设置重试次数，这里为2，实际为3次重试，重试还没成功接收到消息，直接进入死信队列
        redeliveryPolicy.setMaximumRedeliveries(2);
        // 设置初始重试等待时间
        redeliveryPolicy.setInitialRedeliveryDelay(2000);
        // 设置重发策略
        factory.setRedeliveryPolicy(redeliveryPolicy);