Feign默認已經(jīng)整合了Hystrix。

一、使用如何使用

單純服務(wù)降級

• 加配置，默認Feign是不啟用Hystrix的，需要添加配置啟用Hystrix，這樣所有的Feign Client都會受到Hystrix保護！

  feign:
    hystrix:
      enabled: true
  

• 提供Fallback：

  @FeignClient(name = "student-server", fallback = StudentFeignClientFallback.class)
  public interface StudentFeignClient {
    @GetMapping("/student/{id}")
    User findById(@PathVariable("id") Long id);
  }
  
  @Component
  class StudentFeignClientFallback implements StudentFeignClient {
    @Override
    public User findById(Long id) {
      return new User(id, "小i", "大家好，我是聰明的小i", 8);
    }
  }
  

獲得造成fallback的原因

@FeignClient(name = "student-server", fallbackFactory = StudentFeignClientFallbackFactory.class)
public interface StudentFeignClient {
  @GetMapping("/student/{id}")
  User findById(@PathVariable("id") Long id);
}

@Component
@Slf4j
class UserFeignClientFallbackFactory implements FallbackFactory<UserFeignClient> {
  @Override
  public StudentFeignClient create(Throwable throwable) {
    return new UserFeignClient() {
      @Override
      public User findById(Long id) {
        log.error("進入回退邏輯", throwable);
        return new User(id, "小i", "大家好，我是聰明的小i", 8);
      }
    };
  }
}

通過工廠類獲取Fallback的原因(推薦)

@Component
public class StudentFeignFallBackFactory implements FallbackFactory<StudentFeignClient> {
    @Override
    public StudentFeignClient create(Throwable throwable) {
        StudentFeignClientFallback studentFeign = new StudentFeignClientFallback();
        studentFeign.setCause(throwable);
        return studentFeign;
    }
}

二、開關(guān)配置

Feign啟用/禁用Hystrix

1. 全局啟用

feign.hystrix.enabled: true

2. 全局禁用(默認)

feign.hystrix.enabled: false

局部啟用/禁用Hystrix

在@FeignClient的configuration中配置啟用/禁用的配置類。

@FeignClient(name = "student-server", configuration = FeignDisableHystrixConfiguration.class)
public interface StudentFeignClient {
  @GetMapping("/student/{id}")
  User findById(@PathVariable("id") Long id);
}

1. 局部啟用

利用Feign配置的自定義，為指定Feign Client指定如下配置類即可。

public class FeignDisableHystrixConfiguration {
  @Bean
    @Scope("prototype")
    public HystrixFeign.Builder feignBuilder() {
        return HystrixFeign.builder();
    }
}

2. 局部禁用

public class FeignDisableHystrixConfiguration {
  @Bean
    @Scope("prototype")
    public Feign.Builder feignBuilder() {
        return Feign.builder();
    }
}