SpringCloud(八)-手把手教你使用Stream消息驱动

在现在愈益复杂的应用系统中，消息中间件必不可少，而不同的业务也可能会选择不同的消息中间件，比如RabbitMQ或者Kafka。而不同的中间件又有一套不同的逻辑结构，假如一个系统从RabbitMQ换成Kafka，那么将是灾难性的迁移，因此为了解决这个问题，Spring Cloud Stream帮我们屏蔽了消息中间件的差异来实现消息传递。

系列文章
SpringCloud(一)-手把手教你创建springcloud微服务父子项目
 SpringCloud(二)-手把手教你搭建Eureka Server和Eureka Client
SpringCloud(三)-手把手教你通过Rinbbon实现客户端负载均衡
 SpringCloud(四)-手把手教你使用OpenFeign
SpringCloud(五)-手把手教你使用Hystrix配置服务熔断和降级以及Hystrix Dashboard
SpringCloud(六)-手把手教你搭建SpringCloud Config配置中心
 SpringCloud(七)-手把手教你使用消息总线Bus实现动态刷新
 SpringCloud(八)-手把手教你使用Stream消息驱动

1. 简介

Spring Cloud Stream 提供了input，output，binder实现应用程序间的交互，其中output相当于消息发送者，input相当于消息接收者，它们通过binder绑定起来，然后通过通道进行连接。开发者不需要再关注使用到的具体的消息中间件，只需要实现对应的接口即可。

2. 安装RabbitMQ

在笔者的另一篇文章中[RabbitMQ和Kafka:Win10安装教程] (https://www.jianshu.com/p/63d32ab9389f)，已经详细介绍了如何安装和启动RabbitMQ了，如果本机还没安装RabbitMQ的同学请参考上篇文章。

启动成功后的RabbitMQ，在浏览器中输入http://localhost:15672/#/ 可以看到如下界面，就说明RabbitMQ安装和启动成功。

RabbitMQ主界面

3. 搭建stream-producer-8700

新增子项目springcloud-stream-producer-8700(简称stream-producer-8700)，项目的结构如下:

springcloud-stream-producer-8700

3.1 pom.xml引入依赖

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>springcloudtest</artifactId>
        <groupId>com.elio.springcloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>springcloud-stream-producer-8700</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-stream</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-stream-rabbit</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    </dependencies>

    <!--热启动插件-->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <fork>true</fork>
                    <addResources>true</addResources>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

3.2 新增application.yml配置文件

其中cloud.stream.bindings 就是我们要绑定的输出通道，其中myOutput是自定义的

server:
  port: 8700 #端口号

spring:
  application:
    name: springcloud-stream-producer

  rabbitmq:
    host: localhost
    port: 5672
    username: guest
    password: guest

  cloud:
    stream:
      bindings:
        myOutput:
          destination: stream-test

eureka:
  instance:
    instance-id: ${spring.application.name}:${server.port}
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: http://localhost:8300/eureka/,http://localhost:8301/eureka/

3.3 新增StreamProducer8700主启动类

主启动类没有加上什么特殊注解

package com.elio.springcloud;

import com.elio.springcloud.service.MySource;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.stream.annotation.EnableBinding;

@SpringBootApplication
@EnableDiscoveryClient
public class StreamProducer8700 {

    public static void main(String[] args){
        SpringApplication.run(StreamProducer8700.class, args);
    }
}

3.4 新增MySource个性化接口

其实标准的有个Source接口，但是可以自定义，因为实际生产中也是自定义较多。

package com.elio.springcloud.service;

import org.springframework.cloud.stream.annotation.Output;
import org.springframework.messaging.MessageChannel;
import org.springframework.stereotype.Component;

@Component
public interface MySource {

    @Output("myOutput")
    MessageChannel myOutput();
}

3.5 新增SendService服务类

这个服务类将会被controller调用，进行发送消息

package com.elio.springcloud.service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.stream.annotation.EnableBinding;
import org.springframework.cloud.stream.messaging.Source;
import org.springframework.messaging.support.MessageBuilder;

import javax.annotation.Resource;

@EnableBinding({MySource.class})
public class SendService {

    @Autowired
    private  MySource mysource;

    public void sendMsg(String msg){
        mysource.myOutput().send(MessageBuilder.withPayload(msg).build());
    }
}

3.6 新增StreamProducerController类

package com.elio.springcloud.controller;

import com.elio.springcloud.service.SendService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class StreamProducerController {

    @Autowired
    private SendService sendService;

    @GetMapping(value="/send/{msg}")
    public void send(@PathVariable("msg") String msg){
        sendService.sendMsg(msg);
    }
}

4. 搭建stream-consumer-8800

新增springcloud-stream-consumer-8800（简称stream-consumer-8800）作为消息的接收者。

4.1 修改pom.xml引入相关依赖

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>springcloudtest</artifactId>
        <groupId>com.elio.springcloud</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>springcloud-stream-consumer-8800</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-stream</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-stream-rabbit</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    </dependencies>

    <!--热启动插件-->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <fork>true</fork>
                    <addResources>true</addResources>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

4.2 新增application.yml配置文件

其中myInput 是自定义的input

server:
  port: 8800 #端口号

spring:
  application:
    name: springcloud-stream-consumer

  rabbitmq:
    host: localhost
    port: 5672
    username: guest
    password: guest

  cloud:
    stream:
      bindings:
        myInput:
          destination: stream-test

eureka:
  instance:
    instance-id: ${spring.application.name}:${server.port}
  client:
    fetch-registry: true
    register-with-eureka: true
    service-url:
      defaultZone: http://localhost:8300/eureka/,http://localhost:8301/eureka/

4.3 新增StreamConsumer8800主启动类

package com.elio.springcloud;

import com.elio.springcloud.message.MySink;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.stream.annotation.EnableBinding;

@SpringBootApplication
@EnableDiscoveryClient
public class StreamConsumer8800 {

    public static void main(String[] args){
        SpringApplication.run(StreamConsumer8800.class, args);
    }

}

4.4 新增MySink类

package com.elio.springcloud.message;

import org.springframework.cloud.stream.annotation.Input;
import org.springframework.messaging.SubscribableChannel;

public interface MySink {

    @Input("myInput")
    SubscribableChannel myInput();
}

4.5 新增MySink类

package com.elio.springcloud.message;

import org.springframework.cloud.stream.annotation.Input;
import org.springframework.messaging.SubscribableChannel;

public interface MySink {

    @Input("myInput")
    SubscribableChannel myInput();
}

4.6 新增ReceiveService类

package com.elio.springcloud.message;

import org.springframework.cloud.stream.annotation.EnableBinding;
import org.springframework.cloud.stream.annotation.StreamListener;
import org.springframework.stereotype.Service;

@Service
@EnableBinding(MySink.class)
public class ReceiveService {

    @StreamListener("myInput")
    public void recieve(Object payload){
        System.out.println(payload);
    }
}

5. 测试

依次启动eureka-server-8300，eureka-server-8301，stream-producer-8700，stream-consumer-8800，启动成功后，访问stream-producer-8700发送消息接口

http://localhost:8700/send/hello%20world%20stream

然后查看stream-consumer-8800的控制台信息，发现消费者成功的接收到了信息。

image.png

6. 总结

通过这篇文章，我们简单的实现了通过Spring Cloud Stream来实现消息的发送者和接送者，在配置过程中，没有和具体的RabbitMQ进行交互，而是和input, output, binder继续交互，从而屏蔽底层消息中间件细节，达到解耦的效果。