阅读代码块（一）

        以下代码是ActiveMQ中的作为消费者的代码，我会以我自己的理解来逐行的讲解这段代码，同时我是一个小白，一定会有很多问题存在，我会尽可能的去翻阅更多的资料，如果还有问题欢迎大家指出。

// 订阅消息报警
	@PostConstruct
	public void alarm() {
		try {
			ConnectionFactory connectionFactory = ActiveMQutil.getAmqFactory();
			Connection connection = connectionFactory.createConnection();
			if(connection != null){
				connection.start();
				final javax.jms.Session session = connection.createSession(Boolean.TRUE, javax.jms.Session.AUTO_ACKNOWLEDGE);
				Destination  destination = session.createTopic( "队列名" );
				MessageConsumer messageConsumer = session.createConsumer(destination);
				//生成线程池
				final ExecutorService fixedThreadPool = Executors.newFixedThreadPool(2);
				messageConsumer.setMessageListener(new MessageListener() {
					@Override
					public void onMessage(Message message) {
						try {
							//获取队列中消息
							final MapMessage mapMessage = (MapMessage)message;
							fixedThreadPool.e