Spring MVC - Failed to invoke custom ExceptionHandler

Question

I am receiving a strange exception in my application's server log. The exception occurs when a GET request is being made to a certain URL. The URL has the following format -

/some_list/{id}/some_method

handler for which is defined like this -

@RestController
@Validated
public class SomeController {
    @Autowired
    private SomeService someService;

    @RequestMapping(value = "/some_list/{id}/some_method", method = RequestMethod.GET)
    public Collection<SomeObject> getCollection(
        @PathVariable @SomeCustomJavaxConstraintValidator String id,
        @RequestParam(required = true) 
            @SomeCustomJavaxConstraintValidator String someOtherID) {

        return someService.getSomething(id, someOtherID);
    }

    // other methods
}

The exception looks like this (message formatted to fit the question area) -

2016-03-13 14:46:09.956 ERROR org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver - 
Failed to invoke @ExceptionHandler method: 
    public org.springframework.http.ResponseEntity<SomeEntity> 
        com.hogehoge.GenericExceptionHandler.handleServiceException(
            javax.servlet.http.HttpServletResponse, 
            com.hogehoge.CustomException)
java.lang.NullPointerException: Name is null
    at java.lang.Enum.valueOf(Enum.java:236) ~[na:1.8.0_66]
    at org.springframework.http.HttpMethod.valueOf(HttpMethod.java:27) ~[spring-web-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.http.server.ServletServerHttpRequest.getMethod(ServletServerHttpRequest.java:87) ~[spring-web-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.HttpEntityMethodProcessor.handleReturnValue(HttpEntityMethodProcessor.java:175) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:80) ~[spring-web-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:126) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver.doResolveHandlerMethodException(ExceptionHandlerExceptionResolver.java:363) ~[spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerMethodExceptionResolver.doResolveException(AbstractHandlerMethodExceptionResolver.java:60) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver.resolveException(AbstractHandlerExceptionResolver.java:137) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.handler.HandlerExceptionResolverComposite.resolveException(HandlerExceptionResolverComposite.java:74) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.processHandlerException(DispatcherServlet.java:1183) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1020) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:971) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) [tomcat8-servlet-api-8.0.26.jar:na]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) [spring-webmvc-4.2.3.RELEASE.jar:4.2.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) [tomcat8-servlet-api-8.0.26.jar:na]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) [tomcat8-catalina-8.0.26.jar:8.0.26]
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) [tomcat8-coyote-8.0.26.jar:8.0.26]
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673) [tomcat8-coyote-8.0.26.jar:8.0.26]
    at org.apache.tomcat.util.net.Nio2Endpoint$SocketProcessor.doRun(Nio2Endpoint.java:1074) [tomcat8-coyote-8.0.26.jar:8.0.26]
    at org.apache.tomcat.util.net.Nio2Endpoint$SocketProcessor.run(Nio2Endpoint.java:1033) [tomcat8-coyote-8.0.26.jar:8.0.26]
    at org.apache.tomcat.util.net.Nio2Endpoint.processSocket0(Nio2Endpoint.java:594) [tomcat8-coyote-8.0.26.jar:8.0.26]
    at org.apache.tomcat.util.net.Nio2Endpoint.processSocket(Nio2Endpoint.java:578) [tomcat8-coyote-8.0.26.jar:8.0.26]
    at org.apache.tomcat.util.net.SecureNio2Channel$1.completed(SecureNio2Channel.java:86) [tomcat8-coyote-8.0.26.jar:8.0.26]
    at org.apache.tomcat.util.net.SecureNio2Channel$1.completed(SecureNio2Channel.java:79) [tomcat8-coyote-8.0.26.jar:8.0.26]
    at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126) [na:1.8.0_66]
    at sun.nio.ch.Invoker$2.run(Invoker.java:218) [na:1.8.0_66]
    at sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112) [na:1.8.0_66]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_66]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_66]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat8-util-8.0.26.jar:8.0.26]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_66]

GenericExceptionHandler is a @ControllerAdvice which is registered like this -

@ControllerAdvice
public class GenericExceptionHandler {
    // fields and others......

    @ResponseBody
    @ExceptionHandler(CustomException.class)
    public ResponseEntity<SomeEntity> handleServiceException(
        HttpServletResponse response, CustomException e) {

        // method implementation
    }

I could not reproduce this exception in my local environment as the exception apparently occurs at random. I tried to debug it following the stack trace, and it looks like for some reason the getMethod method of HttpServletRequest returns null (!!??), and as a result HttpMethod.valueOf is throwing this exception, but I don't know why this is the case.

Update

Although this is a Spring Boot app, it is being deployed on an independent tomcat server. The POM file has been configured with the maven plugin so that the repackaging is done properly. Also the packaging of the app has been marked as war. Sample -

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>com.hogehoge</groupId>
        <artifactId>some-parent</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

    <artifactId>some-app</artifactId>
    <packaging>war</packaging>

    <!-- Lots of other things -->

    <build>
        <finalName>the-mighty-app</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>

            <!-- Some other plugins -->
        </plugins>
    </build>
</project>

Answer 1

I checked latest Spring source code HttpEntityMethodProcessor.java(around line 175) and I see that code has changed slightly, now it is not possible to get NPE there. I see they switched back and forth a few times between: inputMessage.getMethod() == HttpMethod.GET and inputMessage.getMethod().equals(HttpMethod.GET)