Spring Improve handling of malformed Accept header for @ExceptionHandler methods

Used version

spring-boot: 2.2.4
spring-web: 5.2.3

The issue

If the clients send a malformed Accept header, then the server will fail to respond using @ExceptionHandler and (spring-boot's) ErrorController.

Stacktrace (click to expand)

2020-02-17 12:03:22.721  INFO 24996 --- [io-8081-exec-10] .h.e.e.h.AbstractRequestExceptionHandler : Responding with CONFLICT (HTTP-409): configuration.version_exists_already <<<9Q7w+6sRi+BXyxQT/p0xQr2ibHfUtLZAcy7Yx1mGURo>>>
2020-02-17 12:03:23.746  WARN 24996 --- [io-8081-exec-10] .m.m.a.ExceptionHandlerExceptionResolver : Failure in @ExceptionHandler com.example.errorhandling.handler.RestInvalidRequestExceptionHandler#handleApiException(ApiException)

org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/'
    at org.springframework.web.accept.HeaderContentNegotiationStrategy.resolveMediaTypes(HeaderContentNegotiationStrategy.java:59) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.accept.ContentNegotiationManager.resolveMediaTypes(ContentNegotiationManager.java:124) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.getAcceptableMediaTypes(AbstractMessageConverterMethodProcessor.java:404) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:234) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:226) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:82) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:124) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver.doResolveHandlerMethodException(ExceptionHandlerExceptionResolver.java:407) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerMethodExceptionResolver.doResolveException(AbstractHandlerMethodExceptionResolver.java:61) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:141) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.handler.HandlerExceptionResolverComposite.resolveException(HandlerExceptionResolverComposite.java:80) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1300) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1111) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) [tomcat-embed-websocket-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) [spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) [spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:108) [spring-boot-actuator-2.2.4.RELEASE.jar:2.2.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) [spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) [spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at java.lang.Thread.run(Thread.java:834) [?:?]

2020-02-17 12:03:23.749 ERROR 24996 --- [io-8081-exec-10] o.a.c.c.C.[.[.[.[dispatcherServlet]      : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is com.example.errorhandling.ApiException: configuration.version_exists_already (9Q7w+6sRi+BXyxQT/p0xQr2ibHfUtLZAcy7Yx1mGURo)] with root cause

com.example.errorhandling.ApiException: configuration.version_exists_already (9Q7w+6sRi+BXyxQT/p0xQr2ibHfUtLZAcy7Yx1mGURo)
    at com.example.service.controller.ConfigurationsController.createVersionForType(ConfigurationsController.java:156) ~[classes/:?]
    at com.example.service.controller.ConfigurationsController$$FastClassBySpringCGLIB$$376cd8e3.invoke(<generated>) ~[classes/:?]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:769) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:747) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.validation.beanvalidation.MethodValidationInterceptor.invoke(MethodValidationInterceptor.java:120) ~[spring-context-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:747) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:689) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at com.example.service.controller.ConfigurationsController$$EnhancerBySpringCGLIB$$45cc246d.createVersionForType(<generated>) ~[classes/:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:?]
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
    at java.lang.reflect.Method.invoke(Method.java:566) ~[?:?]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:888) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:108) ~[spring-boot-actuator-2.2.4.RELEASE.jar:2.2.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at java.lang.Thread.run(Thread.java:834) [?:?]

2020-02-17 12:03:23.750 ERROR 24996 --- [io-8081-exec-10] .h.e.e.h.AbstractRequestExceptionHandler : Responding with INTERNAL_SERVER_ERROR (HTTP-500): http.internal_server_error <<<fekDDbaJQS/Fo7RMnKtCeXR4rifwxCFMwFP7rlZEwDo>>>

org.springframework.web.util.NestedServletException: Request processing failed; nested exception is com.example.errorhandling.ApiException: configuration.version_exists_already (9Q7w+6sRi+BXyxQT/p0xQr2ibHfUtLZAcy7Yx1mGURo)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:108) ~[spring-boot-actuator-2.2.4.RELEASE.jar:2.2.4.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) ~[tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at java.lang.Thread.run(Thread.java:834) [?:?]
Caused by: com.example.service.errorhandling.ApiException: configuration.version_exists_already (9Q7w+6sRi+BXyxQT/p0xQr2ibHfUtLZAcy7Yx1mGURo)
    at com.example.service.controller.ConfigurationsController.createVersionForType(ConfigurationsController.java:156) ~[classes/:?]
    at com.example.service.controller.ConfigurationsController$$FastClassBySpringCGLIB$$376cd8e3.invoke(<generated>) ~[classes/:?]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218) ~[spring-core-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:769) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:747) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.validation.beanvalidation.MethodValidationInterceptor.invoke(MethodValidationInterceptor.java:120) ~[spring-context-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:747) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:689) ~[spring-aop-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at com.example.service.controller.ConfigurationsController$$EnhancerBySpringCGLIB$$45cc246d.createVersionForType(<generated>) ~[classes/:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:?]
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?]
    at java.lang.reflect.Method.invoke(Method.java:566) ~[?:?]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:888) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    ... 41 more

2020-02-17 12:03:27.169  INFO 24996 --- [io-8081-exec-10] .h.e.e.h.AbstractRequestExceptionHandler : Responding with NOT_ACCEPTABLE (HTTP-406): request.media_not_acceptable <<<tuHdumnZD0jMbnVw2w44qj+kRgXbqKPsgW0YZ2xfKPw>>>
2020-02-17 12:03:28.650  WARN 24996 --- [io-8081-exec-10] .m.m.a.ExceptionHandlerExceptionResolver : Failure in @ExceptionHandler com.example.errorhandling.handler.InvalidRequestExceptionHandler#handleMediaTypeNotAcceptable(HttpMediaTypeNotAcceptableException)

org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/'
    at org.springframework.web.accept.HeaderContentNegotiationStrategy.resolveMediaTypes(HeaderContentNegotiationStrategy.java:59) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.accept.ContentNegotiationManager.resolveMediaTypes(ContentNegotiationManager.java:124) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.getAcceptableMediaTypes(AbstractMessageConverterMethodProcessor.java:404) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:234) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:181) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:82) ~[spring-web-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:124) ~[spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver.doResolveHandlerMethodException(ExceptionHandlerExceptionResolver.java:407) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerMethodExceptionResolver.doResolveException(AbstractHandlerMethodExceptionResolver.java:61) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:141) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.handler.HandlerExceptionResolverComposite.resolveException(HandlerExceptionResolverComposite.java:80) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1300) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1111) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:660) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) [spring-webmvc-5.2.3.RELEASE.jar:5.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:461) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:384) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:394) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:253) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:348) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:173) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.30.jar:9.0.30]
    at java.lang.Thread.run(Thread.java:834) [?:?]

2020-02-17 12:03:28.650  WARN 24996 --- [io-8081-exec-10] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/']

The error flow is somewhat like this:

A) Throwing a handled exception in the controller method:

Invoke original method
Throw ApiException configuration_conflict
The @ExceptionHandler maps ApiException to an ErrorDTO (409) // Expected to end here
The server fails to parse the Accept header and throws another exception ( NestedServletException)
The ErrorController catches the expection and maps the new exception to an ErrorDTO again (500)
The server fails to parse the Accept header and throws another exception ( HttpMediaTypeNotAcceptableException)
The @ExceptionHandler maps the new exception to an ErrorDTO again (406)
The server/spring(?) determines it cannot respond and just responds with HTTP-406 without body.

B) Returning any DTO from the method

Invoke original method
Return some DTO
The server is unable to parse the Accept header and throws HttpMediaTypeNotAcceptableException
The @ExceptionHandler maps the exception to an ErrorDTO (406) // Expected to end here
The server fails to parse the Accept header
The ErrorController triggers the fallback handling and maps it to an ErrorDTO (406)
The server/spring(?) determines it cannot respond and just responds with HTTP-406 without body.

I expliticly added a HttpMessageConverter that is able to serialize ErrorDTOs to MediaTypes.ALL (forced JSON), but it won't get called at all.

Reproduce

You can reproduce this error by using the following call:

$ curl 'http://localhost:8080/test' -H 'Accept: null' -v
< HTTP/1.1 406
< Content-Length: 0

The following works as expected:

$ curl 'http://localhost:8080/test' -H 'Accept: null/null' -v
< HTTP/1.1 409
< Content-Type: application/json
< Content-Length: 280
<
{
  "errorCode": "configuration.version_exists_already",
  "errorId": "Qd3fZRkJm+of7kk+v22hrvBtcoHSEjt2J1WIsVtJjYE",
  "statusCode": 409
}

Summary

The message converter for HttpMediaTypeNotAcceptableException shouldn't fail due to the very same reason.

Also the WARN log Failure in @ExceptionHandler com.example.errorhandling.handler.InvalidRequestExceptionHandler#handleMediaTypeNotAcceptable(HttpMediaTypeNotAcceptableException) with the stacktrace is confusing, because the method passed successfully, but the server failed to serialize it.

workaround (not tested)

Bypass the HttpMessageConverter and return byte[] directly and thus (hopefully) bypass the parsing of the Accept header.

Comment From: rstoyanchev

Small correction. It's not a message converter where the failure occurs. It's the AbstractMessageConverterMethodProcessor which is trying to perform content negotiation in order to find a compatible message converter.

Suppose we did ignore the HttpMediaTypeNotAcceptableException, we wouldn't know then what media type to render the response with. A 406 error seems an acceptable outcome for what is essentially a bad request.

If you want more control over the parsing of the Accept header you can use the WebMVcConfigurer#configureContentNegotiation, possibly replacing the HeaderContentNegotiationStrategy with an extension that suppresses parsing errors, if it there is something you can rely to fall back on. Or perhaps using */* in you case too.

Comment From: ST-DDT

A 406 error seems an acceptable outcome for what is essentially a bad request.

Yes, that's indeed acceptable. But, it's not acceptable to throw a HTTP-500 in the middle, and I would still like to answer in a self/well-defined error format (instead of the empty 406), even if the request was not valid.

The HTTP-500 won't actually hit the client, because the server fails to send it as well, but it's still in the server's logs.

Comment From: rstoyanchev

But, it's not acceptable to throw a HTTP-500 in the middle

I can't reproduce that 500 error.

@GetMapping(path = "/24539")
public ResponseEntity<Map<String, String>> handle() {
    return ResponseEntity.ok()
            .body(Collections.singletonMap("issue", "24539"));
}

@ExceptionHandler
public ResponseEntity<Map<String, String>> handleEx(HttpMediaTypeNotAcceptableException ex) {
    return ResponseEntity.status(HttpStatus.NOT_ACCEPTABLE)
            .body(Collections.singletonMap("reason", ex.getMessage()));
}

Gives me the following log output.

Click for log output

[http-nio-8080-exec-2] 21:05 [] [/]: Initializing Spring DispatcherServlet 'dispatcherServlet'
[http-nio-8080-exec-2] 21:05 [] DispatcherServlet: Initializing Servlet 'dispatcherServlet'
[http-nio-8080-exec-2] 21:05 [] DispatcherServlet: Detected StandardServletMultipartResolver
[http-nio-8080-exec-2] 21:05 [] DispatcherServlet: enableLoggingRequestDetails='false': request parameters and headers will be masked to prevent unsafe logging of potentially sensitive data
[http-nio-8080-exec-2] 21:05 [] DispatcherServlet: Completed initialization in 14 ms
[http-nio-8080-exec-2] 21:05 [] DispatcherServlet: GET "/24539", parameters={}
[http-nio-8080-exec-2] 21:05 [] RequestMappingHandlerMapping: Mapped to car.app.CarController#handle()
[http-nio-8080-exec-2] 21:05 [] ExceptionHandlerExceptionResolver: Using @ExceptionHandler car.app.CarController#handleEx(HttpMediaTypeNotAcceptableException)
[http-nio-8080-exec-2] 21:05 [] ExceptionHandlerExceptionResolver: Failure in @ExceptionHandler car.app.CarController#handleEx(HttpMediaTypeNotAcceptableException)
org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/'
    at org.springframework.web.accept.HeaderContentNegotiationStrategy.resolveMediaTypes(HeaderContentNegotiationStrategy.java:59)
    at org.springframework.web.accept.ContentNegotiationManager.resolveMediaTypes(ContentNegotiationManager.java:128)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.getAcceptableMediaTypes(AbstractMessageConverterMethodProcessor.java:396)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:226)
    at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:226)
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:82)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:124)
    at org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver.doResolveHandlerMethodException(ExceptionHandlerExceptionResolver.java:407)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodExceptionResolver.doResolveException(AbstractHandlerMethodExceptionResolver.java:61)
    at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:141)
    at org.springframework.web.servlet.handler.HandlerExceptionResolverComposite.resolveException(HandlerExceptionResolverComposite.java:80)
    at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1300)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1111)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)
[http-nio-8080-exec-2] 21:05 [] DefaultHandlerExceptionResolver: Resolved [org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/']
[http-nio-8080-exec-2] 21:05 [] DispatcherServlet: Completed 406 NOT_ACCEPTABLE
[http-nio-8080-exec-2] 21:05 [] DispatcherServlet: "ERROR" dispatch for GET "/error", parameters={}
[http-nio-8080-exec-2] 21:05 [] RequestMappingHandlerMapping: Mapped to org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#error(HttpServletRequest)
[http-nio-8080-exec-2] 21:05 [] ExceptionHandlerExceptionResolver: Using @ExceptionHandler org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#mediaTypeNotAcceptable(HttpServletRequest)
[http-nio-8080-exec-2] 21:05 [] ExceptionHandlerExceptionResolver: Failure in @ExceptionHandler org.springframework.boot.autoconfigure.web.servlet.error.BasicErrorController#mediaTypeNotAcceptable(HttpServletRequest)
org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/'
    at org.springframework.web.accept.HeaderContentNegotiationStrategy.resolveMediaTypes(HeaderContentNegotiationStrategy.java:59)
    at org.springframework.web.accept.ContentNegotiationManager.resolveMediaTypes(ContentNegotiationManager.java:128)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.getAcceptableMediaTypes(AbstractMessageConverterMethodProcessor.java:396)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:226)
    at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:226)
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:82)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:124)
    at org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver.doResolveHandlerMethodException(ExceptionHandlerExceptionResolver.java:407)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodExceptionResolver.doResolveException(AbstractHandlerMethodExceptionResolver.java:61)
    at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:141)
    at org.springframework.web.servlet.handler.HandlerExceptionResolverComposite.resolveException(HandlerExceptionResolverComposite.java:80)
    at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1300)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1111)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:461)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:384)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312)
    at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:394)
    at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:253)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:175)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)
[http-nio-8080-exec-2] 21:05 [] DefaultHandlerExceptionResolver: Resolved [org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/']
[http-nio-8080-exec-2] 21:05 [] DispatcherServlet: Exiting from "ERROR" dispatch, status 406

Note how ExceptionHandlerExceptionResolver returns null if exception handling itself failed in order to allow other resolvers to work. Then you'll see DefaultHandlerExceptionResolver handling it and setting the response to 406. After comes the Boot ERROR dispatch which does fail to render a body but still there is no 500 in the entire sequence.

I would still like to answer in a self/well-defined error format (instead of the empty 406), even if the request was not valid

It just occurred to me that you can preset the content-type of the response, and avoid content negotiation. The following does work:

@ExceptionHandler
public ResponseEntity<Map<String, String>> handleEx(HttpMediaTypeNotAcceptableException ex) {
    return ResponseEntity.status(HttpStatus.NOT_ACCEPTABLE)
            .contentType(MediaType.APPLICATION_JSON)    // <-- this here
            .body(Collections.singletonMap("reason", ex.getMessage()));
}

I'm afraid we as a framework can't ignore a failure to parse the Accept header and go ahead and render anyway. You might be able to do that based in your case(s) and the above shows how you can do that.

Comment From: ST-DDT

Well it's not intuitive to reproduce but it goes like this:

Command: curl http://localhost:8080 -H "Accept: null" -v

Java-Source

package test;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;

import javax.servlet.RequestDispatcher;
import javax.servlet.http.HttpServletRequest;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.error.ErrorController;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@SpringBootApplication
@RestController
public class Test implements ErrorController, WebMvcConfigurer {

    // Application

    public static void main(String... args) {
        SpringApplication.run(Test.class, args);
    }

    @Override
    public void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
        converters.add(0, new ErrorHttpMessageConverter());
    }

    public static class ErrorHttpMessageConverter implements HttpMessageConverter<Object> {

        @Override
        public boolean canRead(Class<?> clazz, MediaType mediaType) {
            return false;
        }

        @Override
        public boolean canWrite(Class<?> clazz, MediaType mediaType) {
            return true; // Usually limited to just the error model
        }

        @Override
        public List<MediaType> getSupportedMediaTypes() {
            return Arrays.asList(MediaType.ALL);
        }

        @Override
        public Object read(Class<? extends Object> clazz, HttpInputMessage inputMessage)
                throws IOException, HttpMessageNotReadableException {
            throw new HttpMessageNotReadableException("Cannot read at all!", inputMessage);
        }

        @Override
        public void write(Object t, MediaType contentType, HttpOutputMessage outputMessage)
                throws IOException, HttpMessageNotWritableException {
            try (OutputStream os = outputMessage.getBody()) {
                os.write(Objects.toString(t).getBytes());
            }
        }

    }

    // Request

    @RequestMapping("/")
    public Object test() {
        System.out.println("Method called");
        throw new ApiException("Validation failed!");
        // return Collections.emptyMap();
    }

    // Main Error Handling

    public static class ApiException extends RuntimeException {

        private static final long serialVersionUID = -4214494053231775872L;

        public ApiException(String message) {
            super(message);
        }

    }

    @ExceptionHandler(Throwable.class)
    @ResponseStatus(HttpStatus.I_AM_A_TEAPOT)
    public Object handle(Throwable e) { // Usually done for each exception type separately
        System.out.println("Handling " + e.getClass().getSimpleName());
        return Collections.singletonMap("error", e.getMessage());
    }

    // Fallback Error Handling

    public static final String ERROR_PATH = "/error";

    @Override
    public String getErrorPath() {
        return ERROR_PATH;
    }

    @RequestMapping("/error")
    public Object fallbackErrorHandler(HttpServletRequest request) {
        HttpStatus status = extractHttpStatus(request);
        String message = extractErrorMessage(request);
        Throwable t = extractErrorException(request);
        String uri = extractErrorRequestUri(request);
        new Exception("Failed to handle error on: " + uri + " (" + status + ") due to " + message, t).printStackTrace();
        Map<String, Object> error = new LinkedHashMap<>();
        error.put("code", status);
        error.put("message", message);
        error.put("uri", uri);
        return error;
    }

    // Helper methods

    private static HttpStatus extractHttpStatus(HttpServletRequest request) {
        return HttpStatus.valueOf((Integer) request.getAttribute(RequestDispatcher.ERROR_STATUS_CODE));
    }

    private String extractErrorMessage(HttpServletRequest request) {
        return (String) request.getAttribute(RequestDispatcher.ERROR_MESSAGE);
    }

    private Throwable extractErrorException(HttpServletRequest request) {
        return (Throwable) request.getAttribute(RequestDispatcher.ERROR_EXCEPTION);
    }

    private String extractErrorRequestUri(HttpServletRequest request) {
        return (String) request.getAttribute(RequestDispatcher.ERROR_REQUEST_URI);
    }

}

Logs

Method called
Handling ApiException
Feb. 24, 2020 5:06:40 NACHM. org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver doResolveHandlerMethodException
WARNUNG: Failure in @ExceptionHandler test.Test#handle(Throwable)
org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/'
    at org.springframework.web.accept.HeaderContentNegotiationStrategy.resolveMediaTypes(HeaderContentNegotiationStrategy.java:59)
    at org.springframework.web.accept.ContentNegotiationManager.resolveMediaTypes(ContentNegotiationManager.java:124)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.getAcceptableMediaTypes(AbstractMessageConverterMethodProcessor.java:404)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:234)
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:181)
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:82)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:124)
    at org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver.doResolveHandlerMethodException(ExceptionHandlerExceptionResolver.java:407)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodExceptionResolver.doResolveException(AbstractHandlerMethodExceptionResolver.java:61)
    at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:141)
    at org.springframework.web.servlet.handler.HandlerExceptionResolverComposite.resolveException(HandlerExceptionResolverComposite.java:80)
    at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1300)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1111)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:834)

Feb. 24, 2020 5:06:40 NACHM. org.apache.catalina.core.StandardWrapperValve invoke
SCHWERWIEGEND: Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is test.Test$ApiException: Validation failed!] with root cause
test.Test$ApiException: Validation failed!
    at test.Test.test(Test.java:84)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:888)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:834)

java.lang.Exception: Failed to handle error on: / (500 INTERNAL_SERVER_ERROR) due to 
    at test.Test.fallbackErrorHandler(Test.java:121)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:888)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:461)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:384)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312)
    at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:394)
    at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:253)
    at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:348)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:173)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: org.springframework.web.util.NestedServletException: Request processing failed; nested exception is test.Test$ApiException: Validation failed!
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1014)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    ... 12 more
Caused by: test.Test$ApiException: Validation failed!
    at test.Test.test(Test.java:84)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:106)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:888)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    ... 37 more
Handling HttpMediaTypeNotAcceptableException
Feb. 24, 2020 5:06:40 NACHM. org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver doResolveHandlerMethodException
WARNUNG: Failure in @ExceptionHandler test.Test#handle(Throwable)
org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/'
    at org.springframework.web.accept.HeaderContentNegotiationStrategy.resolveMediaTypes(HeaderContentNegotiationStrategy.java:59)
    at org.springframework.web.accept.ContentNegotiationManager.resolveMediaTypes(ContentNegotiationManager.java:124)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.getAcceptableMediaTypes(AbstractMessageConverterMethodProcessor.java:404)
    at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:234)
    at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:181)
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:82)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:124)
    at org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver.doResolveHandlerMethodException(ExceptionHandlerExceptionResolver.java:407)
    at org.springframework.web.servlet.handler.AbstractHandlerMethodExceptionResolver.doResolveException(AbstractHandlerMethodExceptionResolver.java:61)
    at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:141)
    at org.springframework.web.servlet.handler.HandlerExceptionResolverComposite.resolveException(HandlerExceptionResolverComposite.java:80)
    at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1300)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1111)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
    at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:461)
    at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:384)
    at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312)
    at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:394)
    at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:253)
    at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:348)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:173)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:367)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:860)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1598)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.base/java.lang.Thread.run(Thread.java:834)

Feb. 24, 2020 5:06:40 NACHM. org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver logException
WARNUNG: Resolved [org.springframework.web.HttpMediaTypeNotAcceptableException: Could not parse 'Accept' header [null]: Invalid mime type "null": does not contain '/']

Shortened logs:

Method called
Handling ApiException // <-- I only want this one
[...]
java.lang.Exception: Failed to handle error on: / (500 INTERNAL_SERVER_ERROR) due to 
[...]
Handling HttpMediaTypeNotAcceptableException // <-- Or maybe this one

I expect to get only one (the second) line in the logs (instead of these 250). Or at least a big fat warning that @ExceptionHandler and ErrorController should define a Content-Type explicitly (must use ResponseBody)

I also found this section regarding the Accept header.

Source

The HyperText Transfer Protocol (HTTP) 406 Not Acceptable client error response code indicates that the server cannot produce a response matching the list of acceptable values defined in the request's proactive content negotiation headers, and that the server is unwilling to supply a default representation.

Proactive content negotiation headers include:

Accept

Accept-Charset

Accept-Encoding

Accept-Language

"Proactive" sounds (to me) like it should be evaluated before the request is processed (especially if it is garbage). Am I mistaken?

Comment From: ST-DDT

I have a suggestion for a non invasive fix for the "could not send response part":

If the parsing of the Accept header fails, then it will check whether the producible content types contains */* and if it does, then it uses that to continue. Because having such a converter means literally "I don't care what you expect".

Comment From: rstoyanchev

Thanks for the sample.

I expect to get only one (the second) line in the logs (instead of these 250). Or at least a big fat warning that @ExceptionHandler and ErrorController should define a Content-Type explicitly (must use ResponseBody)

When an exception handler fails to handle an exception, and we move on to other exception handlers, it is important to log both the exception that could not be handled, and the exception for why it couldn't be handled. Suppressing one or both exceptions at this point omits crucial information.

That said I can see how it gets verbose for this use and we can reduce some of the noise by catching HttpMediaTypeNotAcceptableException as a result of an @ExceptionHandler method and logging something a little more helpful and minimal.

"Proactive" sounds (to me) like it should be evaluated before the request is processed (especially if it is garbage). Am I mistaken?

I think you are. That's just describing what the 406 means. It is not suggesting how to avoid it or take alternative action.

If the parsing of the Accept header fails, then it will check whether the producible content types contains / and if it does, then it uses that to continue. Because having such a converter means literally "I don't care what you expect".

I would consider a controller declaring to produce */* invalid. No controller method can produce anything, and not caring is more or less the same as ignoring the protocol and deciding to render anyway. We can't do that as a framework but you can. The following works fine:

@ExceptionHandler(Throwable.class)
public ResponseEntity<Object> handle(Throwable e) { // Usually done for each exception type separately
    System.out.println("Handling " + e.getClass().getSimpleName());
    return ResponseEntity.status(HttpStatus.I_AM_A_TEAPOT)
            .contentType(MediaType.APPLICATION_JSON)
            .body(Collections.singletonMap("error", e.getMessage()));
}

Comment From: rstoyanchev

So the one improvement I see here is special handling for HttpMediaTypeNotAcceptableException in ExceptionHandlerExceptionResolver to reduce logging a bit.

Comment From: ST-DDT

If the parsing of the Accept header fails, then it will check whether the producible content types contains / and if it does, then it uses that to continue. Because having such a converter means literally "I don't care what you expect".

I would consider a controller declaring to produce */* invalid. No controller method can produce anything, and not caring is more or less the same as ignoring the protocol and deciding to render anyway.

Is an @ExceptionHandler a controller? It doesn't define that it produces */* the HttpMessagrConverter does that to catch cases like the user requested an image, but the server couldn't find it. I can't test it right now, but what does default spring return a for 404 response that requested an image/*. IIRC it returns json/html or nothing, but it won't log weird exceptions or return 406.

I'll try it next week.

Comment From: ST-DDT

I confirmed, that even default spring(-boot) will log a warning in case of a bad Accept header. For me, a user error shouldn't cause a warning in the servers logs.

Comment From: s3curitybug

Any update on this? I'm receiving a lot of exception notifications for one of my cloud applications because someone (maybe a bot) is sending requests with an invalid accept header. It is annoying...

Comment From: rstoyanchev

@s3curitybug the case here is for a failure to parse the Accept header while handling an Exception through an @ExceptionHandler method. Is this your case as well? My suggestion for a fix was to handle HttpMediaTypeNotAcceptableException in ExceptionHandlerExceptionResolver and reduce the logging to a one-line message.

Alternatively you can customize Accept header resolution, see https://github.com/spring-projects/spring-framework/issues/24539#issuecomment-589089804, or fix the Content-Type of the response, see https://github.com/spring-projects/spring-framework/issues/24539#issuecomment-591662182.

Comment From: s3curitybug

@rstoyanchev thank you for your response.

I have a @ControllerAdvice where I control different types of exceptions, and I added an @ExceptionHandler for generic Exception, in order to control any other exception not specifically controlled. In my case, I preffer not to give any information in that case, since this only happens when the user is doing something that cannot be done using the front-end (typically this happens when someone is trying to manipulate the API), so I'm returning a 404 Not Found with no body, but I log the Exception so that I can review these cases in my log explorer:

    @ExceptionHandler
    public ResponseEntity<?> exceptionHandler(
            Exception e) {

        log.info(String.format(
                "Error during the request %s %s",
                request.getMethod(),
                request.getRequestURI()),
                e);

        return new ResponseEntity<>(HttpStatus.NOT_FOUND);

    }

Additionally, my log explorer sends me an email when a log entry of level higher than info is registered. This should not be the case, since I'm using log.info here. For instance, if a user makes a request without a required parameter, or violates a constraint (which happens a lot since my application is exposed to the internet and is constantly receiving random requests from bots and fuzzers), he will receive a 404 Not Found with no body and I will get an info entry in the log explorer, but not en email notification. I only use log.warn and log.error for things I really want to get notified for.

Last days I've been receiving a lot of notifications, and, reviewing the logs, I realized someone (probably a bot) is making requests with an invalid Accept header. This is captured by the generic ExceptionHandler, which produces an info log entry, but then, additionally produces a warn (org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver : Failure in @ExceptionHandler). So I'm constantly getting notified because some bot is sending invalid requests, and my logs are getting flooded with warn level entries. Additionally, the user is not getting a 404, but a 406, which is acceptable but I believe the framework should respect the output I preffer.

I've tried fixing the Content-Type of the response:

    @ExceptionHandler
    public ResponseEntity<?> exceptionHandler(
            Exception e) {

        log.info(String.format(
                "Error during the request %s %s",
                request.getMethod(),
                request.getRequestURI()),
                e);

        return ResponseEntity
                .status(HttpStatus.NOT_FOUND)
                .contentType(MediaType.APPLICATION_OCTET_STREAM)
                .body(null);

    }

This seems to work, so thank you. Anyway, I believe the framework should not behave like this. I understand the response content type is computed from the request accept header, but, if parsing the accept header fails in this point, it should not generate an exception and a warn, it should fallback to a default value, don't you think?

EDIT:

In addition, why is Spring trying to guess the response content type in this scenario? The ResponseEntity body is null, so no content-type header should be returned. I used MediaType.APPLICATION_OCTET_STREAM as a "default" content type, but this response actually should not have a content type header. If I set it to null instead, Spring tries to guess it from the request accept header, which causes the warn again...

EDIT 2:

This seems to work:

    @ExceptionHandler
    @ResponseStatus(HttpStatus.NOT_FOUND)
    public void exceptionHandler(
            Exception e) {

        log.error(String.format(
                "Error during the request %s %s",
                request.getMethod(),
                request.getRequestURI()),
                e);

    }

This code sends a response without content type and does not cause the warning. Is there an inconsistency here? This should be similar to the previous one.

Comment From: ST-DDT

@rstoyanchev Also a javadoc hint regarding these issues in the @ExceptionHandler annotation might be helpful. Although I would prefer it, if the error dispatcher would ignore those errors.

Comment From: rstoyanchev

Thanks for the further detail.

why is Spring trying to guess the response content type in this scenario? The ResponseEntity body is null, so no content-type header should be returned.

I wondered the same. If the response body is null there is no reason to fail because of Accept header parse issues. I see that we currently make a similar body != null check when there are no compatible media types and just avoid the exception, so this should be very similar. We can fix this.

I understand the response content type is computed from the request accept header, but, if parsing the accept header fails in this point, it should not generate an exception and a warn, it should fallback to a default value, don't you think?

We can't choose a default value but I do appreciate that this a client issue. The challenge is it happens on exception handling and as a result obscures what happened. In this case a 406 when Boot tries to add error details. We did fix a similar issue https://github.com/spring-projects/spring-boot/issues/19522 that also resulted in 406 instead of the original and it was fixed by rendering the original status without a body.

I think we can do the same here by rendering the intended error status and skipping the body if the Accept header is malformed. This seems preferable to a 406 without any hint of the original error. I'll experiment with a fix.

Comment From: s3curitybug

Thank you @rstoyanchev.

I realized this also happens in a class implementing the ErrorController interface, not just in @ExceptionHandler methods, for instance, if a request to a non-existent path with an invalid accept header is received. However, the exception is captured by the @ExceptionHandler, if it suits.

Java Source


package xxx;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

import org.springframework.boot.web.error.ErrorAttributeOptions;
import org.springframework.boot.web.servlet.error.ErrorAttributes;
import org.springframework.boot.web.servlet.error.ErrorController;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.context.request.ServletWebRequest;

import lombok.RequiredArgsConstructor;

/**
 * Global Configuration for Error Handling.
 */
@Controller
@RequiredArgsConstructor
public class ErrorHandlingConfig
        implements ErrorController {

    /** Used to retrieve request error attributes. */
    private final ErrorAttributes errorAttributes;

    /** Current Request. */
    private final HttpServletRequest request;

    /** Current Session. */
    private final HttpSession session;

    /**
     * Error handler.
     *
     * @return Unauthorized (401), Forbidden (403) or Not Found (404) with no body.
     */
    @RequestMapping(value = "/error", method = {
            RequestMethod.GET,
            RequestMethod.POST,
            RequestMethod.PUT,
            RequestMethod.DELETE,
            RequestMethod.HEAD,
            RequestMethod.OPTIONS,
            RequestMethod.PATCH,
            RequestMethod.TRACE
    })
    public ResponseEntity<Void> error() {

        Map<String, Object> requestErrorAttributes = errorAttributes.getErrorAttributes(
                new ServletWebRequest(request), ErrorAttributeOptions.defaults());

        HttpStatus errorStatus = HttpStatus.valueOf((Integer) requestErrorAttributes.get("status"));

        if (HttpStatus.UNAUTHORIZED.equals(errorStatus) || HttpStatus.FORBIDDEN.equals(errorStatus)) {

            session.invalidate();

            return ResponseEntity
                    .status(errorStatus)
                    .contentType(null)
                    .body(null);

        } else {

            return ResponseEntity
                    .status(HttpStatus.NOT_FOUND)
                    .contentType(null)
                    .body(null);

        }

    }

    /**
     * @return The path to the error handler.
     */
    @Override
    public String getErrorPath() {

        return "/error";

    }

}

Tell me if you need any further information.