others-How to solve the `feign.FeignException$BadGateway` error when running a springboot application with feign?

1. Purpose

In this post, I would demonstrate how to solve the feign.FeignException$BadGateway error when running a spring boot application with feign.

2022-02-18 15:46:36.101 ERROR 46380 --- [nio-8086-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is feign.FeignException$BadGateway: status 502 reading DemoClient#hello(String)] with root cause


2. The solution

2.1 The details of the problem

2022-02-18 15:46:36.101 ERROR 46380 --- [nio-8086-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is feign.FeignException$BadGateway: status 502 reading DemoClient#hello(String)] with root cause

feign.FeignException$BadGateway: status 502 reading DemoClient#hello(String)
        at feign.FeignException.serverErrorStatus(FeignException.java:199) ~[feign-core-10.4.0.jar:na]
        at feign.FeignException.errorStatus(FeignException.java:144) ~[feign-core-10.4.0.jar:na]
        at feign.FeignException.errorStatus(FeignException.java:133) ~[feign-core-10.4.0.jar:na]
        at feign.codec.ErrorDecoder$Default.decode(ErrorDecoder.java:92) ~[feign-core-10.4.0.jar:na]
        at feign.SynchronousMethodHandler.executeAndDecode(SynchronousMethodHandler.java:151) ~[feign-core-10.4.0.jar:na]
        at feign.SynchronousMethodHandler.invoke(SynchronousMethodHandler.java:80) ~[feign-core-10.4.0.jar:na]
        at feign.ReflectiveFeign$FeignInvocationHandler.invoke(ReflectiveFeign.java:103) ~[feign-core-10.4.0.jar:na]
        at com.sun.proxy.$Proxy98.hello(Unknown Source) ~[na:na]
        at com.example.nacosfeign.clients.DemoController.hello(DemoController.java:19) ~[classes/:na]
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121]
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121]
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
        at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
        at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:892) ~[spring-webmvc-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:797) ~[spring-webmvc-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:626) ~[tomcat-embed-core-9.0.39.jar:4.0.FR]
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) ~[tomcat-embed-core-9.0.39.jar:4.0.FR]
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:94) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.1.19.RELEASE.jar:5.1.19.RELEASE]
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_121]
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_121]
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.39.jar:9.0.39]
        at java.lang.Thread.run(Thread.java:745) [na:1.8.0_121]




2.2 The service provider and feign client

We have defined a method in service provider:

    @GetMapping("hello")
    public Map<String, Object> hello(String name) {
        logger.info("get/hello "+name);
        Map<String, Object> map = new HashMap<>();
        map.put("hello param", name);
        return map;
    }


And the feign client is:

@FeignClient(name="nacos-provider-bswencw1", configuration = FeignConfig.class)
public interface DemoClient {
    @GetMapping("/hello")
    public Map<String, Object> hello(String name);
}



2.3 The reason of the problem

You can find that our provider does not define the method parameter in the request mapping annotation.

 @GetMapping("hello")
 public Map<String, Object> hello(String name) {



2.4 The solution

So the solution is to map the parameters in provider and feign classes

The provider class:

    @GetMapping("hello/{name}")
    public Map<String, Object> hello(@PathVariable String name) {
        logger.info("访问/hello "+name);
        Map<String, Object> map = new HashMap<>();
        map.put("hello param", name);
        return map;
    }

The feign class:

@FeignClient(name="nacos-provider-bswencw1", configuration = FeignConfig.class)
public interface DemoClient {
    @GetMapping("/hello/{name}")
    public Map<String, Object> hello(@PathVariable String name);
}

Now it works!



3. Summary

In this post, I demonstrated how to solve the feign.FeignException$BadGateway error when running a springboot application with feign . The key point is to map the parameters in provider and feign client correctly That’s it, thanks for your reading.

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