常见问题（使用rabbitmq）

消息分组防止多实例重复消费
在一个服务多实例场景下使用默认使用@StreamListener监听消息消费，yml中没有特殊配置的话是会导致消息重复消费的，原因是此时每个实例都是匿名在rabbitmq上注册的队列，需要给消费者指定一个消费组，让消息在组里只被消费一次；

spring.cloud.stream.bindings.xxx(消费者队列名).group=xxx(组名)

在springboot下在同一个服务（项目中）使用@input和@outPut时指定的队列名是不可以重复的.会在启动编译的时候报bean定义重复。需要在yml给生产者和消费者指定同一个交换机。

spring:rabbitmq:host: xxx.xxx.xxx.xxport: 35672username: xxxpassword: xxxvirtual-host: /xxxcloud:stream:bindings:in:#若消息系统是RabbitMQ，目的地（destination）就是指exchange，消息系统是Kafka，那么就是指topicdestination: test#在多实例的时候需要制定一个消息分组，不然每个实例都是匿名方式把队列注册到rabbitmq上去，导致一个交换机下有多个队列#并且默认生成的交换机是topic类型的，会导致重复消费group: myInout:destination: test

先上依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.5.8.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.fchan</groupId><artifactId>springcloudstream</artifactId><version>0.0.1-SNAPSHOT</version><name>springcloudstream</name><description>Demo project for Spring Boot</description><properties><java.version>1.8</java.version></properties><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-stream-rabbit</artifactId>
<!--            <version>2.0.1.RELEASE</version>--></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-actuator</artifactId></dependency></dependencies><dependencyManagement><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-stream-dependencies</artifactId><version>Ditmars.RELEASE</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><build><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin></plugins></build></project>

再上yml配置

spring:rabbitmq:host: xxx.xxx.xxx.xxport: 35672username: xxxpassword: xxxvirtual-host: /xxxcloud:stream:bindings:in:#若消息系统是RabbitMQ，目的地（destination）就是指exchange，消息系统是Kafka，那么就是指topicdestination: test#在多实例的时候需要制定一个消息分组，不然每个实例都是匿名方式把队列注册到rabbitmq上去，导致一个交换机下有多个队列#并且默认生成的交换机是topic类型的，会导致重复消费group: myInout:destination: test

消息生产者

package com.fchan.springcloudstream.service;import org.springframework.cloud.stream.annotation.Input;
import org.springframework.cloud.stream.annotation.Output;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.SubscribableChannel;public interface MyMessageChannel {String out = "out";String in = "in";@Output(out)MessageChannel out();@Input(in)SubscribableChannel in();}

发送消息

package com.fchan.springcloudstream.controller;import com.fchan.springcloudstream.service.MyMessageChannel;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import javax.annotation.Resource;
import java.util.HashMap;
import java.util.Map;@RestController
public class MessageController {@Resourceprivate MyMessageChannel myMessageChannel;@RequestMapping("test")public String testMessage(){Map<String,Object> map = new HashMap<>();map.put("shopId", "123");myMessageChannel.out().send(MessageBuilder.withPayload(map).build());return "success";}}

消息消费者

package com.fchan.springcloudstream.service;import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.cloud.stream.annotation.EnableBinding;
import org.springframework.cloud.stream.annotation.StreamListener;
import org.springframework.messaging.Message;
import org.springframework.stereotype.Component;import java.util.Map;@Component
@EnableBinding({MyMessageChannel.class})
public class MyConsumer {Logger log = LoggerFactory.getLogger(MyConsumer.class);@StreamListener(MyMessageChannel.in)public void input(Message<Map<String,Object>> message){log.info("收到消息：{}", message.getPayload());}}