一、RabbitMQ的RPC简介
实际业务中，有的时候我们还需要等待消费者返回结果给我们，或者是说我们需要消费者上的一个功能、一个方法或是一个接口返回给我们相应的值，而往往大型的系统软件，生产者跟消费者之间都是相互独立的两个系统，部署在两个不同的电脑上，不能通过直接对象.方法的形式获取想要的结果，这时候我们就需要用到RPC（Remote Procedure Call）远程过程调用方式。
RabbitMQ实现RPC的方式很简单，生产者发送一条带有标签（消息ID（correlation_id）+回调队列名称）的消息到发送队列，消费者（也称RPC服务端）从发送队列获取消息并处理业务，解析标签的信息将业务结果发送到指定的回调队列，生产者从回调队列中根据标签的信息获取发送消息的返回结果。
如图，客户端C发送消息，指定消息的ID=rpc_id，回调响应的队列名称为rpc_resp，消息从C发送到rpc_request队列，服务端S获取消息业务处理之后，将correlation_id附加到响应的结果发送到指定的回调队列rpc_resp中，客户端从回调队列获取消息，匹配与发送消息的correlation_id相同的值为消息应答结果。
二、SpringBoot中使用RabbitMQ的RPC功能
注意：springboot中使用的时候，correlation_id为系统自动生成的，reply_to在加载AmqpTemplate实例的时候设置的。
实例：
说明：队列1为发送队列，队列2为返回队列
1.先配置rabbitmq
package com.ws.common;
import org.springframework.amqp.core.Binding;
import org.springframework.amqp.core.BindingBuilder;
import org.springframework.amqp.core.Queue;
import org.springframework.amqp.core.TopicExchange;
import org.springframework.amqp.rabbit.connection.CachingConnectionFactory;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class RabbitMQConfig {
public static final String TOPIC_QUEUE1 = "topic.queue1";
public static final String TOPIC_QUEUE2 = "topic.queue2";
public static final String TOPIC_EXCHANGE = "topic.exchange";
@Value("${spring.rabbitmq.host}")
private String host;
@Value("${spring.rabbitmq.port}")
private int port;
@Value("${spring.rabbitmq.username}")
private String username;
@Value("${spring.rabbitmq.password}")
private String password;
@Autowired
ConnectionFactory connectionFactory;
@Bean(name = "connectionFactory")
public ConnectionFactory connectionFactory() {
CachingConnectionFactory connectionFactory = new CachingConnectionFactory();
connectionFactory.setHost(host);
connectionFactory.setPort(port);
connectionFactory.setUsername(username);
connectionFactory.setPassword(password);
connectionFactory.setVirtualHost("/");
return connectionFactory;
}
@Bean
public RabbitTemplate rabbitTemplate() {
RabbitTemplate rabbitTemplate = new RabbitTemplate(connectionFactory);
//设置reply_to（返回队列，只能在这设置）
rabbitTemplate.setReplyAddress(TOPIC_QUEUE2);
rabbitTemplate.setReplyTimeout(60000);
return rabbitTemplate;
}
//返回队列监听器（必须有）
@Bean(name="replyMessageListenerContainer")
public SimpleMessageListenerContainer createReplyListenerContainer() {
SimpleMessageListenerContainer listenerContainer = new SimpleMessageListenerContainer();
listenerContainer.setConnectionFactory(connectionFactory);
listenerContainer.setQueueNames(TOPIC_QUEUE2);
listenerContainer.setMessageListener(rabbitTemplate());
return listenerContainer;
}
//创建队列
@Bean
public Queue topicQueue1() {
return new Queue(TOPIC_QUEUE1);
}
@Bean
public Queue topicQueue2() {
return new Queue(TOPIC_QUEUE2);
}
//创建交换机
@Bean
public TopicExchange topicExchange() {
return new TopicExchange(TOPIC_EXCHANGE);
}
//交换机与队列进行绑定
@Bean
public Binding topicBinding1() {
return BindingBuilder.bind(topicQueue1()).to(topicExchange()).with(TOPIC_QUEUE1);
}
@Bean
public Binding topicBinding2() {
return BindingBuilder.bind(topicQueue2()).to(topicExchange()).with(TOPIC_QUEUE2);
}
}
2.发送消息并同步等待返回值
@Autowired
private RabbitTemplate rabbitTemplate;
//报文body
String sss = "报文的内容";
//封装Message
Message msg = this.con(sss);
log.info("客户端--------------------"+msg.toString());
//使用sendAndReceive方法完成rpc调用
Message message=rabbitTemplate.sendAndReceive(RabbitMQConfig.TOPIC_EXCHANGE, RabbitMQConfig.TOPIC_QUEUE1, msg);
//提取rpc回应内容body
String response = new String(message.getBody());
log.info("回应：" + response);
log.info("rpc完成---------------------------------------------");
public Message con(String s) {
MessageProperties mp = new MessageProperties();
byte[] src = s.getBytes(Charset.forName("UTF-8"));
//mp.setReplyTo("adsdas"); 加载AmqpTemplate时设置，这里设置没用
//mp.setCorrelationId("2222"); 系统生成，这里设置没用
mp.setContentType("application/json");
mp.setContentEncoding("UTF-8");
mp.setContentLength((long)s.length());
return new Message(src, mp);
}
3.写消费者
package com.ws.listener.mq;
import java.nio.charset.Charset;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageProperties;
import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import com.ws.common.RabbitMQConfig;
import lombok.extern.slf4j.Slf4j;
@Slf4j
@Component
public class Receiver {
@Autowired
private RabbitTemplate rabbitTemplate;
@RabbitListener(queues=RabbitMQConfig.TOPIC_QUEUE1)
public void receiveTopic1(Message msg) {
log.info("队列1:"+msg.toString());
String msgBody = new String(msg.getBody());
//数据处理，返回的Message
Message repMsg = con(msgBody+"返回了", msg.getMessageProperties().getCorrelationId());
rabbitTemplate.send(RabbitMQConfig.TOPIC_EXCHANGE, RabbitMQConfig.TOPIC_QUEUE2, repMsg);
}
@RabbitListener(queues=RabbitMQConfig.TOPIC_QUEUE2)
public void receiveTopic2(Message msg) {
log.info("队列2:"+msg.toString());
}
public Message con(String s, String id) {
MessageProperties mp = new MessageProperties();
byte[] src = s.getBytes(Charset.forName("UTF-8"));
mp.setContentType("application/json");
mp.setContentEncoding("UTF-8");
mp.setCorrelationId(id);
return new Message(src, mp);
}
}
日志打印：
2019-06-26 17:11:16.607 [http-nio-8080-exec-4] INFO com.ws.controller.UserController - 客户端--------------------(Body:‘报文的内容' MessageProperties [headers={}, contentType=application/json, contentEncoding=UTF-8, contentLength=5, deliveryMode=PERSISTENT, priority=0, deliveryTag=0])
2019-06-26 17:11:16.618 [SimpleAsyncTaskExecutor-1] INFO com.ws.listener.mq.Receiver - 队列1:(Body:‘报文的内容' MessageProperties [headers={}, correlationId=1, replyTo=topic.queue2, contentType=application/json, contentEncoding=UTF-8, contentLength=0, receivedDeliveryMode=PERSISTENT, priority=0, redelivered=false, receivedExchange=topic.exchange, receivedRoutingKey=topic.queue1, deliveryTag=1, consumerTag=amq.ctag-8IzlhblYmTebqUYd-uferw, consumerQueue=topic.queue1])
2019-06-26 17:11:16.623 [http-nio-8080-exec-4] INFO com.ws.controller.UserController - 回应：报文的内容返回了
2019-06-26 17:11:16.623 [http-nio-8080-exec-4] INFO com.ws.controller.UserController - rpc完成---------------------------------------------
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