spring cloud Feign导入jar失败

Feign导入jar失败的问题

网上很多人在使用的feign时在pom.xml中填写的是

   <dependency> 
      <groupId>org.springframework.cloud</groupId> 
      <artifactId>spring-cloud-starter-feign</artifactId> 
    </dependency>

但是在我个人的使用过程中没能成功，像上面填好后一直报错，说没有指定版本，后来我有百度看是怎么回事：

    <dependency> 
      <groupId>org.springframework.cloud</groupId> 
      <artifactId>spring-cloud-starter-feign</artifactId> 
      <version>1.3.1.RELEASE</version> 
    </dependency>

变成这个有版本号的了，以为成功了，准备写@FeignClient发现没有这个标签，这下把我玩够了，又在百度上找问题所在。

有的说是可能没有下载完成导致的需要重新导入，搞了好久都没有解决。最后我尝试了最笨的方法，修改版本号看行不行，结果行了，把我玩够了。下面这个在pom.xml 中导入就么有问题。

    <dependency> 
      <groupId>org.springframework.cloud</groupId> 
      <artifactId>spring-cloud-starter-feign</artifactId> 
      <version>1.4.1.RELEASE</version> 
    </dependency>

经过自己在学习中发现

用以下的方式也能够完美导入feign

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>

最后分析了一下可能是因为feign的版本更新太快导致的吧。

Springcloud feign 异常报错及解决

报错异常如下

There was an unexpected error (type=Internal Server Error, status=500).
Type definition error: [simple type, class demo.domain.ApiResult]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `demo.domain.ApiResult` (no Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator) at [Source: (PushbackInputStream); line: 1, column: 2]

Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is feign.FeignException$InternalServerError: status 500 reading FeignService#test()] with root cause

feign.FeignException$InternalServerError: status 500 reading FeignService#test()
    at feign.FeignException.errorStatus(FeignException.java:114) ~[feign-core-10.2.3.jar:na]
    at feign.FeignException.errorStatus(FeignException.java:86) ~[feign-core-10.2.3.jar:na]
    at feign.codec.ErrorDecoder$Default.decode(ErrorDecoder.java:93) ~[feign-core-10.2.3.jar:na]
    at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:149) ~[feign-core-10.2.3.jar:na]
    at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:78) ~[feign-core-10.2.3.jar:na]
    at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103) ~[feign-core-10.2.3.jar:na]
    at com.sun.proxy.$Proxy77.test(Unknown Source) ~[na:na]
    at demo.controller.ConsumerController.test(ConsumerController.java:25) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_221]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_221]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_221]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_221]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1039) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:118) ~[spring-web-5.1.9.RELEASE.jar:5.1.9.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:853) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1587) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_221]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_221]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.22.jar:9.0.22]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_221]

其原因是 feign 传递对象没有空构造方法 或 没有 get/set 方法

这里是我报错前的代码

可以看到我这个ApiResult并没有get/set及空构造方法

添加后即可 更推荐使用lombok的@Data注解

改造后

浏览器访问可以正常请求

以上为个人经验，希望能给大家一个参考，也希望大家多多支持。