MQ全称为Message Queue, 即消息队列。MQ是一种应用程序对应用程序的通信方法。应用程序通过读写出入队列的消息（针对应用程序的数据）来通信，而无需专用连接来链接它们。消息传递指的是程序之间通过在消息中发送数据进行通信，而不是通过直接调用彼此来通信，直接调用通常是用于诸如远程过程调用的技术。排队指的是应用程序通过队列来通信。队列的使用除去了接收和发送应用程序同时执行的要求。RabbitMQ则是一个在AMQP基础上完整的，可复用的企业消息系统。

RabbitMQ安装与启动

安装命令

终端中输入以下命令

brew update
brew install rabbitmq

配置RabbitMQ

安装完成后需要将/usr/local/sbin添加到环境变量中

打开.bash_profile文件

vim ~/.bash_profile

将 PATH=/usr/local/sbin:$PATH 加入文件

通过:wq命令保持文件并退出

source ~/.bash_profile

启动RabbitMQ

终端中输入以下命令

rabbitmq-server

登录Web管理界面

浏览器地址栏输入 http://localhost:15672/，账户密码默认 guest

Hello RabbitMQ

通过一个实例来体验RabbitMQ的使用方法。

添加依赖包

在pom.xml文件中新增dependency


    com.rabbitmq
    amqp-client
    3.6.5

Send实现

public class Send {
    private final static String QUEUE_NAME = "hello";
    public static void main(String[] argv)
            throws java.io.IOException {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = null;
        Channel channel = null;
        try {
            connection = factory.newConnection();
            channel = connection.createChannel();
            channel.queueDeclare(QUEUE_NAME, false, false, false, null);
            String message = "Hello Rabbit!";
            channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
            System.out.println(" [x] Sent '" + message + "'");
        } catch (TimeoutException e) {
            e.printStackTrace();
        } finally {
            try {
                channel.close();
            } catch (TimeoutException e) {
                e.printStackTrace();
            }
            connection.close();
        }
    }
}

Recv实现

public class Recv {
    private final static String QUEUE_NAME = "hello";
    public static void main(String[] argv)
            throws java.io.IOException,
            java.lang.InterruptedException {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = null;
        try {
            connection = factory.newConnection();
        } catch (TimeoutException e) {
            e.printStackTrace();
        }
        Channel channel = connection.createChannel();
        channel.queueDeclare(QUEUE_NAME, false, false, false, null);
        System.out.println(" [*] Waiting for messages. To exit press CTRL+C");
        Consumer consumer = new DefaultConsumer(channel) {
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body)
                    throws IOException {
                String message = new String(body, "UTF-8");
                System.out.println(" [x] Received '" + message + "'");
            }
        };
        channel.basicConsume(QUEUE_NAME, true, consumer);
    }
}

测试结果

多次运行Send类 [x] Sent 'Hello Rabbit!'可以通过界面查看在消息队列中暂存的消息。

此时运行Recv类可以读取消息队列中的消息

[*] Waiting for messages. To exit press CTRL+C
[x] Received 'Hello Rabbit!'
[x] Received 'Hello Rabbit!'
[x] Received 'Hello Rabbit!'