作者：海向 \
起源：https://www.cnblogs.com/haixi…
RabbitMQ 简述
RabbitMQ 是一个音讯代理：它承受并转发音讯。您能够将其视为邮局：当您将要把寄发的邮件投递到邮箱中时，您能够确信 Postman 学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，用来承受，存储和转发二进制数据块的音讯。
队列就像是在 RabbitMQ 中表演邮箱的角色。尽管音讯通过 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度的限度，它实质上是一个大的音讯缓冲区。许多生产者能够发送到一个队列的音讯，许多消费者能够尝试从一个队列接收数据。
producer 即为生产者，用来产生音讯发送给队列。consumer 是消费者，须要去读队列内的音讯。producer，consumer 和 broker(rabbitMQ server)不用驻留在同一个主机上; 的确在大多数应用程序中它们是这样散布的。
简略队列
简略队列是最简略的一种模式，由生产者、队列、消费者组成。生产者将音讯发送给队列，消费者从队列中读取音讯实现生产。
在下图中，“P”是咱们的生产者，“C”是咱们的消费者。两头的框是队列 – RabbitMQ 代表消费者的音讯缓冲区。
java 形式
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. 创立一个 ConnectionFactory 并进行设置
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
factory.setVirtualHost("/");
factory.setUsername("guest");
factory.setPassword("guest");
//2. 通过连贯工厂来创立连贯
Connection connection = factory.newConnection();
//3. 通过 Connection 来创立 Channel
Channel channel = connection.createChannel();
// 理论场景中，音讯多为 json 格局的对象
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. 敞开连贯
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. 创立一个 ConnectionFactory 并进行设置
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
factory.setVirtualHost("/");
factory.setUsername("guest");
factory.setPassword("guest");
//2. 通过连贯工厂来创立连贯
Connection connection = factory.newConnection();
//3. 通过 Connection 来创立 Channel
Channel channel = connection.createChannel();
//4. 申明一个队列
channel.queueDeclare(QUEUE_NAME, true, false, false, null);
System.out.println("[*] Waiting for messages. To exit press CTRL+C");
/*
true: 示意主动确认，只有音讯从队列中获取，无论消费者获取到音讯后是否胜利生产，都会认为音讯曾经胜利生产
false: 示意手动确认，消费者获取音讯后，服务器会将该音讯标记为不可用状态，期待消费者的反馈，如果消费者一
直没有反馈，那么该音讯将始终处于不可用状态，并且服务器会认为该消费者曾经挂掉，不会再给其发送音讯，直到该消费者反馈。*/
//5. 创立消费者并接管音讯
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 : hello
Send message2 : hello
Send message3 : hello
[*] Waiting for messages. To exit press CTRL+C
[x] Received 'hello'
[x] Received 'hello'
[x] Received 'hello'当咱们启动生产者之后查看 RabbitMQ 治理后盾能够看到有一条音讯正在期待被生产。
当咱们启动消费者之后再次查看，能够看到积压的一条音讯曾经被生产。
总结
队列申明 queueDeclare 的参数：第一个参数示意队列名称、第二个参数为是否长久化（true 示意是，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（创建者能够应用的公有队列，断开后主动删除）、第四个参数为当所有消费者客户端连贯断开时是否主动删除队列、第五个参数为队列的其余参数。
basicConsume 的第二个参数 autoAck: 应答模式，true：自动应答，即消费者获取到音讯，该音讯就会从队列中删除掉，false：手动应答，当从队列中取出音讯后，须要程序员手动调用办法应答，如果没有应答，该音讯还会再放进队列中，就会呈现该音讯始终没有被生产掉的景象。
这种简略队列的模式，零碎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，当你手动创立一个队列时，零碎会主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 与队列名称雷同，相当于 channel.queueBind(queue:"QUEUE_NAME", exchange:"(AMQP default)“, routingKey:"QUEUE_NAME"); 尽管实例没有显式申明交换机，然而当路由键和队列名称一样时，就会将音讯发送到这个默认的交换机中。这种形式比较简单，然而无奈满足简单的业务需要，所以通常在生产环境中很少应用这种形式。
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，或从缺省替换中解除绑定。它也不能被删除。
——引自 RabbitMQ 官网文档
spring-amqp 形式
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>应用测试
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);
}
}参考办法
/**
* 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
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