ExceptionHandlerExceptionResolver warns when re-throwing the exception cause

[arlowhite]

spring-framework/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ExceptionHandlerExceptionResolver.java

Line 412 in 3d913b8

if (invocationEx != exception && logger.isWarnEnabled()) {

If an @ExceptionHandler method matches and rethrows a cause of the root exception, it will always log this warning. Instead, the warning should only be logged if the exception differs from the one bound to the ExceptionHandler method's parameter.

Instead, this code should do something like this:

        Throwable evaluatedException = null;
        try {
            if (logger.isTraceEnabled()) {
                logger.trace("Invoking @ExceptionHandler method: " + exceptionHandlerMethod);
            }
            Throwable cause = exception.getCause();
            if (cause != null) {
                // Expose cause as provided argument as well
                evaluatedException = cause;
                exceptionHandlerMethod.invokeAndHandle(webRequest, mavContainer, exception, cause, handlerMethod);
            }
            else {
                // Otherwise, just the given exception as-is
                evaluatedException = exception;
                exceptionHandlerMethod.invokeAndHandle(webRequest, mavContainer, exception, handlerMethod);
            }
        }
        catch (Throwable invocationEx) {
            // Any other than the original exception is unintended here,
            // probably an accident (e.g. failed assertion or the like).
            if (invocationEx != evaluatedException && logger.isWarnEnabled()) {
                logger.warn("Failed to invoke @ExceptionHandler method: " + exceptionHandlerMethod, invocationEx);
            }
            // Continue with default processing of the original exception...
            return null;
        }

I'm testing on Spring 4.3.24, but the code appears to be the same.

[rstoyanchev]

Both the top level exception and the cause are made available, so we should be checking both. The exception handler method could be re-throwing either one.