最近在做微服务的学习，发现在使用feign做服务调用时，使用继承的方式调用服务，加入Hystrix的熔断处理fallback配置时，会报错，代码如下：

@RequestMapping("/demo/api") public interface HelloApi {      @GetMapping("user/{id}")     User getUserById(@PathVariable("id") long id);      @GetMapping("hello")     String echo(@RequestParam("name") String name); }

@FeignClient(value = "ms-server", fallback = ConsumerFeignServiceFallBack.class) public interface ConsumerFeignService extends HelloApi {  }

@Component public class ConsumerFeignServiceFallBack implements ConsumerFeignService {     @Override     public User getUserById(long id) {         return new User();     }      @Override     public String echo(String name) {         return "echo error: " + name;     } }

报错如下：

Caused by: java.lang.IllegalStateException: Ambiguous mapping. Cannot map 'com.thoughtworks.demo.consumer.service.ConsumerFeignService' method  public abstract java.lang.String com.thoughtworks.demo.api.HelloApi.echo(java.lang.String) to {[/demo/api/hello],methods=[GET]}: There is already 'consumerFeignServiceFallBack' bean method public java.lang.String com.thoughtworks.demo.consumer.service.ConsumerFeignServiceFallBack.echo(java.lang.String) mapped. 	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.assertUniqueMethodMapping(AbstractHandlerMethodMapping.java:576) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE] 	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.register(AbstractHandlerMethodMapping.java:540) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE] 	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.registerHandlerMethod(AbstractHandlerMethodMapping.java:264) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE] 	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.detectHandlerMethods(AbstractHandlerMethodMapping.java:250) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE] 	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.initHandlerMethods(AbstractHandlerMethodMapping.java:214) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE] 	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.afterPropertiesSet(AbstractHandlerMethodMapping.java:184) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE] 	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping.afterPropertiesSet(RequestMappingHandlerMapping.java:127) ~[spring-webmvc-4.3.14.RELEASE.jar:4.3.14.RELEASE] 	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1687) ~[spring-beans-4.3.14.RELEASE.jar:4.3.14.RELEASE] 	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1624) ~[spring-beans-4.3.14.RELEASE.jar:4.3.14.RELEASE] 	... 21 common frames omitted

错误原因是这里继承的接口类是一个controller接口，继承时会继承到父类的

@RequestMapping("/demo/api")

SpringMvc在做mapping映射的时候发现ConsumerFeignService和ConsumerFeignServiceFallBack的mapping重复了，所以抛出异常，如何解决呢？

解决的方法有2个：

一是更改ConsumerFeignServiceFallBack的mapping配置，代码如下：

@Component @RequestMapping("fallback/demo/api") public class ConsumerFeignServiceFallBack implements ConsumerFeignService {     @Override     public User getUserById(long id) {         return new User();     }      @Override     public String echo(String name) {         return "echo error: " + name;     } }

二是使用fallbackFactory，代码如下：

@Component public class ConsumerFeignServiceFallBack implements FallbackFactory<ConsumerFeignService> {      @Override     public ConsumerFeignService create(Throwable cause) {         return new ConsumerFeignService() {             @Override             public User getUserById(long id) {                 return new User();             }              @Override             public String echo(String name) {                 return "echo error: " + name;             }         };     } }

运行后，关闭服务提供者，发现熔断并没有生效，没有像单独使用@HystrixCommand时进入fallback方法，查了很多方式，发现原来是feign的hystix的配置开关没有打开

解决方法，在application.yml中增加配置如下：

feign:   hystrix:     enabled: true

在IntelliJ IDEA里也没有这个配置的提示，还报告警告，不知道算不算是个BUG，这里我使用的版本是

springBootVersion = '1.5.10.RELEASE' springCloudVersion = 'Edgware.SR3'

以上就是我在使用feign时发现的一些小坑，如有问题，欢迎随时拍砖~