RabbitMQ 之简单队列

RabbitMQ 简述
简单队列
java 方式
spring-amqp方式

RabbitMQ 简述

RabbitMQ是一个消息代理：它接受并转发消息。您可以将其视为邮局：当您将要把寄发的邮件投递到邮箱中时，您可以确信Postman 先生最终会将邮件发送给收件人。在这个比喻中，RabbitMQ是一个邮箱，邮局和邮递员，用来接受，存储和转发二进制数据块的消息。

队列就像是在RabbitMQ中扮演邮箱的角色。虽然消息经过RabbitMQ和应用程序，但它们只能存储在队列中。队列只受主机的内存和磁盘限制的限制，它本质上是一个大的消息缓冲区。许多生产者可以发送到一个队列的消息，许多消费者可以尝试从一个队列接收数据。

producer即为生产者，用来产生消息发送给队列。consumer是消费者，需要去读队列内的消息。producer，consumer和broker(rabbitMQ server)不必驻留在同一个主机上;确实在大多数应用程序中它们是这样分布的。

简单队列

简单队列是最简单的一种模式，由生产者、队列、消费者组成。生产者将消息发送给队列，消费者从队列中读取消息完成消费。

在下图中，“P”是我们的生产者，“C”是我们的消费者。中间的框是队列 - RabbitMQ代表消费者的消息缓冲区。

java 方式

生产者

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

public class MyProducer {
    private static final String QUEUE_NAME = "ITEM_QUEUE";

    public static void main(String[] args) throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        //初始化链接工厂
        initFactory(factory);
        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();
        channel.queueDeclare(QUEUE_NAME,false, false, false, null);
        //实际场景中，消息多为json格式的对象
        String msg = "hello";
        channel.basicPublish("", QUEUE_NAME, null, msg.getBytes());
        System.out.println("Send message : " + msg);
      
        channel.close();
        connection.close();
    }

    private static void initFactory(ConnectionFactory factory) {
        factory.setHost("localhost");
        factory.setVirtualHost("/");
        factory.setUsername("guest");
        factory.setPassword("guest");
    }
}

    /**
     * Declare a queue
     * @param queue the name of the queue
     * @param durable true if we are declaring a durable queue (the queue will survive a server restart)
     * @param exclusive true if we are declaring an exclusive queue (restricted to this connection)
     * @param autoDelete true if we are declaring an autodelete queue (server will delete it when no longer in use)
     * @param arguments other properties (construction arguments) for the queue
     * @return a declaration-confirm method to indicate the queue was successfully declared
     * @throws java.io.IOException if an error is encountered
     */
    Queue.DeclareOk queueDeclare(String queue, boolean durable, boolean exclusive, boolean autoDelete,Map<String, Object> arguments) throws IOException;

    /**
     * Publish a message
     * @see com.rabbitmq.client.AMQP.Basic.Publish
     * @param exchange the exchange to publish the message to
     * @param routingKey the routing key
     * @param props other properties for the message - routing headers etc
     * @param body the message body
     * @throws java.io.IOException if an error is encountered
     */
    void basicPublish(String exchange, String routingKey, BasicProperties props, byte[] body) throws IOException;


    /**
     * Start a non-nolocal, non-exclusive consumer, with
     * a server-generated consumerTag.
     * @param queue the name of the queue
     * @param autoAck true if the server should consider messages
     * acknowledged once delivered; false if the server should expect
     * explicit acknowledgements
     * @param callback an interface to the consumer object
     * @return the consumerTag generated by the server
     * @throws java.io.IOException if an error is encountered
     * @see com.rabbitmq.client.AMQP.Basic.Consume
     * @see com.rabbitmq.client.AMQP.Basic.ConsumeOk
     * @see #basicConsume(String, boolean, String, boolean, boolean, Map, Consumer)
     */
    String basicConsume(String queue, boolean autoAck, Consumer callback) throws IOException;

消费者

import com.rabbitmq.client.*;
import java.io.IOException;

public class MyConsumer {
    private static final String QUEUE_NAME = "ITEM_QUEUE";

    public static void main(String[] args) throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        initFactory(factory);
        factory.setHost("localhost");
        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();
        channel.queueDeclare(QUEUE_NAME, false, false, false, null);
        //声明队列是幂等的 - 只有当它不存在时才会被创建,这里声明队列不是必须的，但是我们可能会在
        //publisher之前启动消费者，所以我们要确保队列存在，然后再尝试从中消费消息
        System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

        /*
           true:表示自动确认，只要消息从队列中获取，无论消费者获取到消息后是否成功消费，都会认为消
                    息已经成功消费
           false:表示手动确认，消费者获取消息后，服务器会将该消息标记为不可用状态，等待消费者的反馈，
                                如果消费者一直没有反馈，那么该消息将一直处于不可用状态，并且服务器会认为该消费者已经
                                挂掉，不会再给其发送消息，直到该消费者反馈。
        */
        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);
    }

    private static void initFactory(ConnectionFactory factory) {
        factory.setHost("localhost");
        factory.setVirtualHost("/");
        factory.setUsername("guest");
        factory.setPassword("guest");
    }
}

Send message : hello

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

spring-amqp方式

引入 Maven 依赖

        <dependency>
            <groupId>com.rabbitmq</groupId>
            <artifactId>amqp-client</artifactId>
            <version>5.6.0</version>
        </dependency>        
                <dependency>
            <groupId>org.springframework.amqp</groupId>
            <artifactId>spring-rabbit</artifactId>
            <version>2.1.5.RELEASE</version>
        </dependency>

spring 配置文件

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:rabbit="http://www.springframework.org/schema/rabbit"
       xsi:schemaLocation="http://www.springframework.org/schema/rabbit
           https://www.springframework.org/schema/rabbit/spring-rabbit.xsd
           http://www.springframework.org/schema/beans
           https://www.springframework.org/schema/beans/spring-beans.xsd">

    <rabbit:connection-factory id="connectionFactory" host="localhost" virtual-host="/"
    username="guest" password="guest"/>
    <rabbit:template id="amqpTemplate" connection-factory="connectionFactory"/>
    <rabbit:admin connection-factory="connectionFactory"/>
    <rabbit:queue name="MY-QUEUE"/>
</beans>

使用测试

import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Main {
    public static void main(String[] args) {
        ApplicationContext app = new ClassPathXmlApplicationContext("spring/rabbit-context.xml");
        AmqpTemplate amqpTemplate = app.getBean(AmqpTemplate.class);
        amqpTemplate.convertAndSend("MY-QUEUE", "Item");
        String msg = (String) amqpTemplate.receiveAndConvert("MY-QUEUE");
        System.out.println(msg);
    }
}

参考方法

/**
 * Convert a Java object to an Amqp {@link Message} and send it to a specific exchange
 * with a specific routing key.
 *
 * @param exchange the name of the exchange
 * @param routingKey the routing key
 * @param message a message to send
 * @throws AmqpException if there is a problem
 */
void convertAndSend(String exchange, String routingKey, Object message) throws AmqpException;
/**
     * Receive a message if there is one from a specific queue and convert it to a Java
     * object. Returns immediately, possibly with a null value.
     *
     * @param queueName the name of the queue to poll
     * @return a message or null if there is none waiting
     * @throws AmqpException if there is a problem
     */
@Nullable
Object receiveAndConvert(String queueName) throws AmqpException;