Spring Cloud Stream 使用笔记

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zhangyue

#Spring Cloud Stream
Spring 已经对JMS中间件做了很多封装，比如Spring对ampq队列协议的封装`spring-rabbit.jar``,以及企业集成的实现`Spring Integration`(解决服务间的异步通讯交互问题),而Spring Cloud Stream是对针对消息中间件的进一步封装,Stream已经支持Kafka/Rabbit MQ/Redis/Gemfire.

Spring Cloud Stream官网模型图如下：
**![](https://leanote.com/api/file/getImage?fileId=5a0d7305ab6441677d002467)**

- Middleware:一些消息中间件，如Kafka/RabbitMQ
- Binder：粘合剂，将Middleware和Stream应用粘合起来，不同Middleware对应不同的Binder。初始化一些中间件的连接信息
- Channel：通道，应用程序通过一个明确的Binder与外界（中间件）通信。消息发布使用output通道，消息监听使用input通道
- ApplicationCore：Stream自己实现的消息机制封装，包括分区、分组、发布订阅的语义，与具体中间件无关，这会让开发人员很容易地以相同的代码使用不同类型的中间件。

> 官方定义:Spring Cloud Stream是构建消息驱动的微服务应用程序的框架。Spring Cloud Stream基于Spring Boot建立独立的生产级Spring应用程序，并使用Spring Integration提供与消息代理的连接。它提供了来自几家供应商的中间件的意见配置，介绍了持久发布订阅语义，消费者组和分区的概念。
Spring Integration

# 使用
## 1. 配置
```
#设置接受者input的队列名称 这里的test_channel 对应@Input或@Output的value
spring.cloud.stream.bindings.test_channel.destination=sink-channel
spring.cloud.stream.bindings.test_channel2.destination=sink-channel2

#rabbitMQ服务器地址 配置rabbit
spring.cloud.stream.binders.rabbit.type=rabbit
#environment 属性会在spring stream加载时加载环境变量属性中，会影视业到RabbitProperties
spring.cloud.stream.binders.rabbit.environment.spring.rabbitmq.host=localhost
spring.cloud.stream.binders.rabbit.environment.spring.rabbitmq.port=5672
spring.cloud.stream.binders.rabbit.environment.spring.rabbitmq.username=guest
spring.cloud.stream.binders.rabbit.environment.spring.rabbitmq.password=guest
spring.cloud.stream.binders.rabbit.environment.spring.rabbitmq.virtual-host=/
```

## 2.声明channel的inputs和outputs
```
public interface MyChannel {

/**
     * 这里的 test_channel 对应配置文件中的 spring.cloud.stream.bindings.test_channel
     */
    String TEST_CHANNEL = "test_channel";

@Input(TEST_CHANNEL)
    SubscribableChannel testChannelInput();

@Output(TEST_CHANNEL)
    MessageChannel testChannelOutput();

//-----------------------------

String TEST_CHANNEL_TOW = "test_channel2";

@Input(TEST_CHANNEL_TOW)
    SubscribableChannel testChannelInputTow();

@Output(TEST_CHANNEL_TOW)
    MessageChannel testChannelOutputTow();
}
```
> 如果@Input未指定value时默认就是方法名,@Input和@Output的value对应配置中的spring.cloud.stream.bindings.*, 使用@Output注解是，改channel必须在配置文件中配置初始化，否则将报错` Dispatcher has no subscribers`

## 3. 开启`MyChannel`接口的实现，在启动类中加上`@EnableBinding({MyChannel.class})`,spring将会为其启动生成实现类
```
@Slf4j
@EnableBinding({MyChannel.class,Processor.class})
@SpringBootApplication
public class BootApplication {

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

}

```

## 4. 使用注解`@InboundChannelAdapter(MyChannel.TEST_CHANNEL)`绑定生产者
```
@Slf4j
@Service
public class ProducerService {

@InboundChannelAdapter(MyChannel.TEST_CHANNEL)
    public String timerMessageSource() {
        String format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
        log.info("publish message success:"+format);
        return format;
    }
}
```
`@InboundChannelAdapter`默认在后台开启一个定时任务，每隔1s执行一次

# 5. 使用注解`@StreamListener`或者`@ServiceActivator`监听队列消息
```
@Slf4j
@Service
public class ReceiverService {

/**
     * @StreamListener 是Stream提供的注解，Spring Integration也有一个类似功能的注解@ServiceActivator，两者都有监听通道功能，
     * 区别是@StreamListener可以根据contentType去解析数据，比如一个json格式的数据，@StreamListener可以自动解析成Java bean
     * @param payload
     */
    @ServiceActivator(inputChannel = MyChannel.TEST_CHANNEL, outputChannel = MyChannel.TEST_CHANNEL_TOW)
    //@StreamListener(MyChannel.TEST_CHANNEL)//读取input通道的数据
    //@SendTo(MyChannel.TEST_CHANNEL)//经过方法处理后输出到output通道
    public String receivedMsg(Object payload) {
        log.info("Received--" + payload);
        return "Received--" + payload;
    }

@StreamListener(MyChannel.TEST_CHANNEL_TOW)//读取input通道的数据
    public void receivedChannelTow(Object payload) {
        log.info("Received Tow: " + payload);
    }

}
```
## 6.执行结果
```
2017-11-16 18:55:16.423  INFO 42168 --- [ask-scheduler-5] com.okeeper.service.ProducerService      : publish message success:2017-11-16 18:55:16
2017-11-16 18:55:16.423  INFO 42168 --- [ask-scheduler-5] com.okeeper.service.ReceiverService      : Received--2017-11-16 18:55:16
2017-11-16 18:55:16.423  INFO 42168 --- [ask-scheduler-5] com.okeeper.service.ReceiverService      : Received Tow: Received--2017-11-16 18:55:16
2017-11-16 18:55:17.424  INFO 42168 --- [ask-scheduler-5] com.okeeper.service.ProducerService      : publish message success:2017-11-16 18:55:17
2017-11-16 18:55:17.424  INFO 42168 --- [ask-scheduler-5] com.okeeper.service.ReceiverService      : Received--2017-11-16 18:55:17
2017-11-16 18:55:17.424  INFO 42168 --- [ask-scheduler-5] com.okeeper.service.ReceiverService      : Received Tow: Received--2017-11-16 18:55:17
2017-11-16 18:55:18.426  INFO 42168 --- [ask-scheduler-5] com.okeeper.service.ProducerService      : publish message success:2017-11-16 18:55:18
2017-11-16 18:55:18.426  INFO 42168 --- [ask-scheduler-5] com.okeeper.service.ReceiverService      : Received--2017-11-16 18:55:18
2017-11-16 18:55:18.426  INFO 42168 --- [ask-scheduler-5] com.okeeper.service.ReceiverService      : Received Tow: Received--2017-11-16 18:55:18
```
每隔一秒执行一次

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