异常的报错信息通常有以下几种:

 feign.FeignException: status 404 reading

Json exception:syntax error 404 等等(主要报错信息)

问题的根源是:消费者找不到想要调用的方法，也就是你定义的 Feign 客户端接口与被调用接口不一致。要么是请求方式、请求路径不匹配，要么就是参数不匹配，只要认真核对，不难纠正错误。

下面举一个网上的例子:在 portal-test-service 项目中，指定了 context-path 属性，调用 portal-test-service 接口会加上 /portalWsg 前缀。

server:
  port: 9990
  context-path: /portalWsg

然而，我在定义 Feign 接口的时候，忘记加上 /portalWsg 前缀，代码如下：

@FeignClient(name = "portal-test-service")
public interface IPortalInterface {

    @RequestMapping(value = "/system/v1/SysUserWsg/queryList", method = RequestMethod.GET)
    @ResponseBody
    PortalResult queryListByObj(@RequestParam("id") String id);

}

于是报错，截取部分信息如下：

feign.FeignException: status 404 reading IPortalInterface#queryListByObj(String)
    at feign.FeignException.errorStatus(FeignException.java:62) ~[feign-core-9.5.0.jar:?]
    at feign.codec.ErrorDecoder$Default.decode(ErrorDecoder.java:91) ~[feign-core-9.5.0.jar:?]
    at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:138) ~[feign-core-9.5.0.jar:?]
    at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:76) ~[feign-core-9.5.0.jar:?]
    at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103) ~[feign-core-9.5.0.jar:?]
    at com.sun.proxy.$Proxy296.queryListByObj(Unknown Source) ~[?:?]
    at com.sitech.cmap.paasplatform.wsg.controller.workorder.PortalTestController.listUsers(PortalTestController.java:33) ~[classes/:?]
    at com.sitech.cmap.paasplatform.wsg.controller.workorder.PortalTestController$$FastClassBySpringCGLIB$$b7108cc2.invoke(<generated>) ~[classes/:?]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738) ~[spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at org.springframework.aop.aspectj.MethodInvocationProceedingJoinPoint.proceed(MethodInvocationProceedingJoinPoint.java:85) ~[spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at com.sitech.cmap.wsg.common.aspect.WsgResultAspect.handlerControllerMethod(WsgResultAspect.java:36) [wsg-extension-3.1.0-SNAPSHOT.jar:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_91]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_91]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_91]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_91]
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethodWithGivenArgs(AbstractAspectJAdvice.java:629) [spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at org.springframework.aop.aspectj.AbstractAspectJAdvice.invokeAdviceMethod(AbstractAspectJAdvice.java:618) [spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at org.springframework.aop.aspectj.AspectJAroundAdvice.invoke(AspectJAroundAdvice.java:70) [spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92) [spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) [spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673) [spring-aop-4.3.11.RELEASE.jar:4.3.11.RELEASE]
    at com.sitech.cmap.paasplatform.wsg.controller.workorder.PortalTestController$$EnhancerBySpringCGLIB$$dd10d04f.listUsers(<generated>) [classes/:?]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_91]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_91]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_91]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_91]

路径同时加上 /portalWsg 前缀，问题便得到解决！

@FeignClient(name = "portal-test-service")
public interface IPortalInterface {

    @RequestMapping(value = "/portalWsg/system/v1/SysUserWsg/queryList", method = RequestMethod.GET)
    @ResponseBody
    PortalResult queryListByObj(@RequestParam("id") String id);

}

特别说明:以上例子来源于https://www.jianshu.com/p/2745cc19a6da