Spring-boot: Enable WARN logging with DefaultHandlerExceptionResolver

[philwebb]

Currently if an exception such as MissingServletRequestParameterException is thrown no stack-trace is logged. It would be useful to provide an option to add them.

Something like this in EnableWebMvcConfiguration:

        @Override
        protected void configureHandlerExceptionResolvers(
                List<HandlerExceptionResolver> exceptionResolvers) {
            addDefaultHandlerExceptionResolvers(exceptionResolvers);
            for (HandlerExceptionResolver resolver : exceptionResolvers) {
                if (resolver instanceof DefaultHandlerExceptionResolver) {
                    ((DefaultHandlerExceptionResolver) resolver)
                            .setWarnLogCategory(DefaultHandlerExceptionResolver.class
                                    .getName());
                }
            }
        }

I'm not sure if this should be on or off by default.

[philwebb]

@wilkinsona @dsyer Any thoughts about this? Trying to debug #2162 highlighted the problem. Not sure if we should enable by default because the logs could get pretty full just by people posting incomplete data.

[wilkinsona]

Tricky one. On the one hand, it could be used as a form of DoS attack if you managed to flood the logs with exception messages. On the other hand, it'd make problem diagnosis easier.

I could be convinced either way but perhaps we should err toward secure by default and default to off?

[philwebb]

Moving to 1.3. Could be another good candidate to enable during development but not in production.

[chrylis]

I'm not familiar enough with the internals of the MVC chain post-controller to say whether mine is a duplicate, but they're semantically related. This one seems to be dealing with resolving controller arguments, and mine is about exceptions thrown after the controller has returned an argument during JSON/XML serialization.

[snicoll]

@philwebb I gave that a try, you can find a proposal (see https://github.com/snicoll/spring-boot/commit/745671a99a4ec48e3aca055480bc74b0ef057fbe)

Let's assume I have added a @ResponseStatus annotation on a custom exception, here's what I get for a _single_ call to the service that throws that exception:

2016-05-24 13:28:05.641  WARN 97219 --- [nio-8080-exec-1] .m.m.a.ExceptionHandlerExceptionResolver : Handler execution resulted in exception: com.example.DemoApplication$MyException
2016-05-24 13:28:05.643  WARN 97219 --- [nio-8080-exec-1] .w.s.m.a.ResponseStatusExceptionResolver : Handler execution resulted in exception: com.example.DemoApplication$MyException

Your proposal above does not work as MVC ships with 3 "default" resolvers and that default is the fallback. Spring MVC logs the exception even if the handler does not ultimately resolve the model (that's what happens with ExceptionHandlerExceptionResolver).

Long story short:

• Enabling only DefaultHandlerExceptionResolver looks incomplete to me: there are two other implementations _before_ this one that have a chance to resolve the exception
• Enabling all 3 defaults can easily lead to duplicate warning log

Thoughts?

[celiovasconcelos]

Tested in 1.3.5.RELEASE

I was forced to workaround like this:

@Slf4j //lombok
@ResponseStatus(HttpStatus.BAD_REQUEST)
public class MyCustomException extends RuntimeException {

  public MyCustomException(String msg) {
    super(msg);
    log.warn(msg, this);
  }

}

Otherwise, no way to see my custom exception in the log.

[bclozel]

SPR-14392 has been fixed.

You should now get a single WARN log when the exception is actually resolved, like this:

[.m.m.a.ExceptionHandlerExceptionResolver] - Resolved exception caused by Handler execution: java.lang.IllegalStateException

@snicoll I think you can now merge your proposal.

[fedotxxl]

Exception has been correctly processed by ExceptionHandler. What's the point to log it? What's the point to log it at WARN level? What's the point to enable it by default?

[TorosyanV]

When I have ControllerAdvice and have method anotated with ExceptionHandler and I'm doing redirect ExceptionHandlerExceptionResolver logs with WARN level.
Why?
I already handled custom exception and logged it

[wilkinsona]

ExceptionHandlerExceptionResolver is part of Spring Framework. If you have a question about it, please ask on Stack Overflow. If you have a suggestion for an improvement, please open a JIRA ticket.

[MSMTFaro]

@TorosyanV I have same issue and having to fix by setting log level to ERROR. I wonder if you found a better way.
org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver: ERROR