这篇文章主要介绍了RabbitMQ简单队列实例及原理解析,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下

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

package com.anqi.mq.nat;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 { //1. 创建一个 ConnectionFactory 并进行设置 ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); factory.setVirtualHost("/"); factory.setUsername("guest"); factory.setPassword("guest"); //2. 通过连接工厂来创建连接 Connection connection = factory.newConnection(); //3. 通过 Connection 来创建 Channel Channel channel = connection.createChannel(); //实际场景中，消息多为json格式的对象 String msg = "hello"; //4. 发送三条数据 for (int i = 1; i <= 3 ; i++) { channel.basicPublish("", QUEUE_NAME, null, msg.getBytes()); System.out.println("Send message" + i +" : " + msg); } //5. 关闭连接 channel.close(); connection.close(); }} /** * 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

package com.anqi.mq.nat;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 { //1. 创建一个 ConnectionFactory 并进行设置 ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); factory.setVirtualHost("/"); factory.setUsername("guest"); factory.setPassword("guest"); //2. 通过连接工厂来创建连接 Connection connection = factory.newConnection(); //3. 通过 Connection 来创建 Channel Channel channel = connection.createChannel(); //4. 声明一个队列 channel.queueDeclare(QUEUE_NAME, true, false, false, null); System.out.println(" [*] Waiting for messages. To exit press CTRL+C"); //5. 创建消费者并接收消息 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 + "'"); } }; //6. 设置 Channel 消费者绑定队列 channel.basicConsume(QUEUE_NAME, true, consumer); }}Send message1 : helloSend message2 : helloSend message3 : hello [*] Waiting for messages. To exit press CTRL+C [x] Received 'hello' [x] Received 'hello' [x] Received 'hello'

当我们启动生产者之后查看RabbitMQ管理后台可以看到有一条消息正在等待被消费。

当我们启动消费者之后再次查看，可以看到积压的一条消息已经被消费。

总结

• 队列声明queueDeclare的参数：第一个参数表示队列名称、第二个参数为是否持久化（true表示是，队列将在服务器重启时生存）、第三个参数为是否是独占队列（创建者可以使用的私有队列，断开后自动删除）、第四个参数为当所有消费者客户端连接断开时是否自动删除队列、第五个参数为队列的其他参数。
• basicConsume的第二个参数autoAck: 应答模式，true：自动应答，即消费者获取到消息，该消息就会从队列中删除掉，false：手动应答，当从队列中取出消息后，需要程序员手动调用方法应答，如果没有应答，该消息还会再放进队列中，就会出现该消息一直没有被消费掉的现象。
• 这种简单队列的模式，系统会为每个队列隐式地绑定一个默认交换机，交换机名称为" (AMQP default)"，类型为直连 direct，当你手动创建一个队列时，系统会自动将这个队列绑定到一个名称为空的 Direct 类型的交换机上，绑定的路由键 routing key 与队列名称相同，相当于channel.queueBind(queue:"QUEUE_NAME", exchange:"(AMQP default)“, routingKey:"QUEUE_NAME");虽然实例没有显式声明交换机，但是当路由键和队列名称一样时，就会将消息发送到这个默认的交换机中。这种方式比较简单，但是无法满足复杂的业务需求，所以通常在生产环境中很少使用这种方式。
• The default exchange is implicitly bound to every queue, with a routing key equal to the queue name. It is not possible to explicitly bind to, or unbind from the default exchange. It also cannot be deleted.默认交换机隐式绑定到每个队列，其中路由键等于队列名称。不可能显式绑定到，或从缺省交换中解除绑定。它也不能被删除。——引自 RabbitMQ 官方文档

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 */@NullableObject receiveAndConvert(String queueName) throws AmqpException;

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