spring-cloud-alibaba学习实例（4）--集成Feign

spring-cloud-alibaba学习实例（4）–集成FeignClient
Feign是一个声明式WebService客户端.使用Feign能让编写WebService客户端更加简单,它的使用方法是定义一个接口,然后在上面添加注解,同时也支持JAX-RS标准的注解.Feign也支持可拔插式的编码器和解码器.Spring Cloud对Feign进行了封装,使其支持了Spring MVC标准注解
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我们知道，想要开启FeignClient，首先要素就是添加@EnableFeignClients注解。其主要功能是初始化FeignClient的配置和动态执行client的请求。
环境：jdk 1.8
idea
sping-cloud-alibaba 2.2.1.RELEASE
sping-boot 2.2.5.RELEASE
sping-cloud Hoxtom.SR3
1首先建立一个三个子模块，结构如下图。其中demo-producer用来提供服务A，demo-consumer用来rpc调用服务A。

2在demo-rpc-feigh中加入需要依赖的jar包

    
  org.springframework.cloud</groupId>
  spring-cloud-starter-openfeign</artifactId>
</dependency>
         
             com.alibaba.cloud</groupId>
             spring-cloud-starter-alibaba-nacos-config</artifactId>
         </dependency>

        
            org.springframework.boot</groupId>
            spring-boot-starter-web</artifactId>
        </dependency>

        
            org.springframework.boot</groupId>
            spring-boot-starter-actuator</artifactId>
        </dependency>
        
            com.alibaba.cloud</groupId>
            spring-cloud-starter-alibaba-sentinel</artifactId>
        </dependency>
        
            com.alibaba.cloud</groupId>
            spring-cloud-starter-alibaba-nacos-discovery</artifactId>
        </dependency>

        
            com.alibaba.csp</groupId>
            sentinel-datasource-nacos</artifactId>

        </dependency>

3 在demo-producer中引入配置文件bootstrap.yml和application.yml
bootstrap.yml

server.port: 8080
spring.application.name: nacos-config
spring.profiles.active: develop
spring.cloud.nacos.config.server-addr: 127.0.0.1:8848
spring.cloud.nacos.config.file-extension: yaml
spring.cloud.nacos.config.refresh.enabled: true

application.yml

在这里插入代码片

4 编写服务代码ProducerService，ProducerServiceImpl，ProducerApplication

public interface ProducerService {
    public  String  testProducer(String  msg);
}

@Service
public class ProducerServiceImpl implements ProducerService {
    @Override
    public String testProducer(String  msg) {
        return "调用producer成功!! "+msg;
    }
}
@SpringBootApplication
@EnableDiscoveryClient
public class ProducerApplication {
    public static void main(String[] args) {

        SpringApplication.run(ProducerApplication.class,args);
    }
}

5编写一个TestPoducerController

@RestController
public class TestPoducerController {
    @Autowired
    ProducerService producerService;
    @GetMapping("/teseProducer")
    public  String  testProducer(String  msg){
        String producer = producerService.testProducer(msg);
        return producer;
    }
}

6启动demo-producer 测试一下

7编写demo-consumer
配置文件修改 bootstrap.yml 和application.yml
bootstrap.yml

server.port: 8082
spring.application.name: demo-consumer
spring.profiles.active: develop
spring.cloud.nacos.config.server-addr: 127.0.0.1:8848
spring.cloud.nacos.config.file-extension: yaml
spring.cloud.nacos.config.refresh.enabled: true

application.yml

feign:
  sentinel:
    enabled: true


management:
  endpoints:
    web:
      exposure:
        include: "*"

8编写 controller 和service 和启动类

@RestController
public class TestConsumerController {
    @Autowired
    RpcProducerService rpcProducerService;

    @GetMapping("/tesetRpc")
    public  String  tesetRpc(String  msg){
        String testProducer = rpcProducerService.testProducer("我是消费者，我来调用rpc");
        return testProducer;
    }
}
@FeignClient(name = "demo-producer")

public interface RpcProducerService {
    @GetMapping("/teseProducer")
    public  String  testProducer(@RequestParam  String  msg);
}


@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ConsumerApplication {
    public static void main(String[] args) {

        SpringApplication.run(ConsumerApplication.class,args);
    }
}

说明 @FeignClient(name = “demo-producer”) 说明在这个service上面开启rpc调用，name是服务提供方的服务名称。 @GetMapping("/teseProducer")
public String testProducer(String msg);
这个必须要和服务提供方的controller接口一样

因为feigh底层是使用http协议的。
@EnableFeignClients表明项目开启了feigh功能
9启动domo-consumer 测试一下



10如何实现fallback
在demo-consumer中增加类，修改一个类
如下

@Component
public class RpcProducerServiceImp implements RpcProducerService {
    @Override
    public String testProducer(String msg) {
        return "不好意思，调用失败";
    }
}
@FeignClient(name = "demo-producer",fallback = RpcProducerServiceImp.class )

public interface RpcProducerService {
    @GetMapping("/teseProducer")
    public  String  testProducer(@RequestParam  String  msg);
}

@FeignClient(name = “demo-producer”,fallback = RpcProducerServiceImp.class )
其中fallback指定调用失败，会如何处理。
11测试一下，我们停掉demo-producer,制造调用失败场景

demo-producer已经被停掉了

github地址 https://github.com/userliyazhou/spirng-cloud-alibaba-project-demo/tree/master/alibaba-project-parent/demo-rpc-feigh