【SpringBoot学习笔记】运行错误：No fallback instance of type class found for feign client

[[报错情况：]]

feign中使用Hystrix，报错：No fallback instance of type class  found for feign client 

[源码：]

@FeignClient(value = "eureka-client", configuration = FeignConfig.class, fallback = HiHystrix.class)
public interface EurekaClientFeign {
    @GetMapping(value = "/hi")
    String sayHiFromClientEureka(@RequestParam(value = "name") String name);
}

@Component
public class HiHystrix implements EurekaClientFeign {
    @Override
    public String sayHiFromClientEureka(String name) {
        return "hi," + name + ",sorry,error!";
    }
}

[[原因和解决办法：]]
“HiHystrix”类实现“EurekaClientFeign”接口时，缺少注解“@Component”，导致编译时未将“HiHystrix”类自动实例化，当服务接口不可用时，进入到熔断器fallback的逻辑处理中，此时检查不到对应的实例，将无法使用，因此虽然编译器没检查到语法错误但运行时报错。