SpringCloud学习笔记（九、SpringCloud Stream）

目录：

• 什么是SpringCloud Stream
• 如何使用SpringCloud Stream
• 消息分流

什么是SpringCloud Stream：

SpringCloud Stream是一个用于构建消息驱动的微服务应用框架。它通过注入，输入、输出通道来与外界通信；因此它很容易实现消息的中转，并且在更换消息中间件的时候不需要该代码，仅需要修改配置即可。支持的消息中间件如RabbitMQ、Kafka等等。

如何使用SpringCloud Stream（以RabbitMQ为例）：

1、增加maven依赖

 <dependency>
     <groupId>org.springframework.cloud</groupId>
     <artifactId>spring-cloud-stream</artifactId>
 </dependency>
 <dependency>
     <groupId>org.springframework.cloud</groupId>
     <artifactId>spring-cloud-stream-binder-rabbit</artifactId>
 </dependency>
 <dependency>
     <groupId>org.springframework.cloud</groupId>
     <artifactId>spring-cloud-stream-test-support</artifactId>
     <scope>test</scope>
 </dependency>

2、增加properties配置

 spring.application.name=stream
 server.port=7070

 # rabbitmq
 spring.rabbitmq.host=localhost
 spring.rabbitmq.port=5672
 spring.rabbitmq.username=guest
 spring.rabbitmq.password=guest

 # stream
 spring.cloud.stream.bindings.input.destination=customer
 spring.cloud.stream.bindings.output.destination=customer

3、启动类加上本工程的消息代理类型

@EnableBinding({Processor.class})

@EnableBinding分为三种类型

）org.springframework.cloud.stream.messaging.Processor：接收和发送消息

）org.springframework.cloud.stream.messaging.Source：仅支持发送消息

）org.springframework.cloud.stream.messaging.Sink：仅支持接收消息

4、加上Controller及Service

 @RestController
 @AllArgsConstructor
 public class ProcessorController {

     private final ProcessorService processorService;

     @GetMapping("/testProcessor/{message}")
     public boolean testProcessor(@PathVariable("message") String message) {
         return processorService.send(message);
     }
 }

 @Service
 @AllArgsConstructor
 public class ProcessorService {

     private final Processor processor;

     public boolean send(String message) {
         return processor.output().send(MessageBuilder.withPayload(message).build());
     }

     public boolean subscribe(MessageHandler handler) {
         return processor.input().subscribe(handler);
     }
 }

5、在任意bean下写上接收逻辑或另起一个工程（另一个工程的mq需要配成一个哦）

 @StreamListener(Sink.INPUT)
 public void receive(String message) {
     System.err.println("receive message: " + message);
 }

然后我们启动项目，访问http://localhost:7070/testProcessor/hello，此时就会在控制台看到receive message: hello的字样。

消息分流（kafka特性）：

 @GetMapping("/testMessageShunt/{type}")
 public boolean testMessageShunt(@PathVariable("type") String type) {
     String header = "a".equalsIgnoreCase(type) ? "msg1" : "msg2";
     return processorService.send(type, header);
 }

 /**
  * RabbitMQ不支持消息分流
  */
 @StreamListener(value = Sink.INPUT, condition = "headers['contentType']=='mgs1'")
 public void receiveMessage1(@Payload Message<String> message) {
     System.err.println("receive message1: " + message.getPayload());
 }

 /**
  * RabbitMQ不支持消息分流
  */
 @StreamListener(value = Sink.INPUT, condition = "headers['contentType']=='mgs2'")
 public void receiveMessage2(@Payload Message<String> message) {
     System.err.println("receive message2: " + message.getPayload());
 }