当在使用feign时做服务降级产生的一个错误： There is already 'XXXXX' bean method

启动服务报错：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'requestMappingHandlerMapping' defined in class path resource [org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration$EnableWebMvcConfiguration.class]: Invocation of init method failed; nested exception is java.lang.IllegalStateException: Ambiguous mapping. Cannot map 'com.itheima.order.feign.ProductFeignClient' method 
public abstract com.itheima.order.entity.Product com.itheima.order.feign.ProductFeignClient.findById(java.lang.Long)
to {GET /product/{id}}: There is already 'productFeignClientFallBack' bean method
public com.itheima.order.entity.Product com.itheima.order.feign.ProductFeignClientFallBack.findById(java.lang.Long) mapped.
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1778) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:845) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:877) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:742) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:389) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:311) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1213) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1202) [spring-boot-2.1.6.RELEASE.jar:2.1.6.RELEASE]
	at com.itheima.order.OrderServerApplication.main(OrderServerApplication.java:17) [classes/:na]
Caused by: java.lang.IllegalStateException: Ambiguous mapping. Cannot map 'com.itheima.order.feign.ProductFeignClient' method 
public abstract com.itheima.order.entity.Product com.itheima.order.feign.ProductFeignClient.findById(java.lang.Long)
to {GET /product/{id}}: There is already 'productFeignClientFallBack' bean method
public com.itheima.order.entity.Product com.itheima.order.feign.ProductFeignClientFallBack.findById(java.lang.Long) mapped.
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.assertUniqueMethodMapping(AbstractHandlerMethodMapping.java:618) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping$MappingRegistry.register(AbstractHandlerMethodMapping.java:586) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.registerHandlerMethod(AbstractHandlerMethodMapping.java:312) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.lambda$detectHandlerMethods$1(AbstractHandlerMethodMapping.java:282) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at java.util.LinkedHashMap.forEach(LinkedHashMap.java:684) ~[na:1.8.0_221]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.detectHandlerMethods(AbstractHandlerMethodMapping.java:280) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.processCandidateBean(AbstractHandlerMethodMapping.java:252) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.initHandlerMethods(AbstractHandlerMethodMapping.java:211) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.web.servlet.handler.AbstractHandlerMethodMapping.afterPropertiesSet(AbstractHandlerMethodMapping.java:199) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping.afterPropertiesSet(RequestMappingHandlerMapping.java:164) ~[spring-webmvc-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1837) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1774) ~[spring-beans-5.1.8.RELEASE.jar:5.1.8.RELEASE]
	... 16 common frames omitted

 There is already 'productFeignClientFallBack' bean method

主要是这句 查询网上发现说是重复url地址了

我feign的设置是这样的

@FeignClient(name= "server-product",fallback = ProductFeignClientFallBack.class)
@RequestMapping("/product")
public interface ProductFeignClient {
    /**
     * 配置需要调用的接口
     */
    @GetMapping("/{id}")
    public Product findById(@PathVariable("id")Long id);

}

服务降级:

@Component
public class ProductFeignClientFallBack implements ProductFeignClient{


    public Product findById(Long id) {
        Product product = new Product();
        product.setProductName("请求参数失败");
        return product;
    }
}

测试了多次发现是确实是url的问题
把feign调用url的类RequestMapping去掉即可，加到方法中

@FeignClient(name = "server-product",fallback = ProductFeignClientFallBack.class)
public interface ProductFeignClient {
    /**
     * 配置需要调用的接口
     */
    @GetMapping("product/{id}")
    public Product findById(@PathVariable("id")Long id);

}

启动成功
记个坑，要用服务降级就不要在类上设置RequestMapping了。
都加在方法中即可！！！