Kotlin - Spring REST - ControllerAdvice with ExceptionHandler won't get invoked

Question

In order to simplify my error handling i wanted an ExceptionHandler, i have used the 4. point on http://www.baeldung.com/exception-handling-for-rest-with-spring .

My exception handler class looks like follows:

@ControllerAdvice
class APIExceptionHandler : ResponseEntityExceptionHandler() {

    @ExceptionHandler(value = [(TestException::class)])
    fun handleConflict(exception: TestException, request: WebRequest): ResponseEntity<Any> {
        println("Handle")
        return handleExceptionInternal(exception, "Response Body", HttpHeaders(), HttpStatus.BAD_REQUEST, request)
    }
}

TestException is just a simple Exception that extends RuntimeException

class TestException : RuntimeException()

Anyhow, in my RestController i am simply throwing an exception as soon as any call is made:

@GetMapping("/lobby/close")
fun closeLobby(@RequestParam(value = "uuid") uuid: String, @RequestHeader(value = "userSession") userSession: String): ResponseEntity<Any> {
    throw TestException()
}

But the exception handler is not invoked.

However, calling this:

@GetMapping("/lobby/error")
fun error(): ResponseEntity<Any> {
    throw TestException()
}

it is invoked.

I don't quite understand what the difference is, besides of the first version expecting parameters and a specific header.

UPDATE 24.03.2018

The problem seems to be, that the ExceptionHandler isn't being invoked if the clients request was malformed.

By default a malformed request leads to a pretty detailed error report, but the custom ExceptionHandler seems to disable this functionality.

Answer 1

I got it working, here is my code.

@ControllerAdvice
class ControllerAdviceRequestError : ResponseEntityExceptionHandler() {
    @ExceptionHandler(value = [(UserAlreadyExistsException::class)])
    fun handleUserAlreadyExists(ex: UserAlreadyExistsException,request: WebRequest): ResponseEntity<ErrorsDetails> {
        val errorDetails = ErrorsDetails(Date(),
                "Validation Failed",
                ex.message!!
        )
        return ResponseEntity(errorDetails, HttpStatus.BAD_REQUEST)
    }
}

Exception class

class UserAlreadyExistsException(override val message: String?) : Exception(message)

Data class

data class ErrorsDetails(val time: Date, val message: String, val details: String)

MyController:

@PostMapping(value = ["/register"])
    fun register(@Valid @RequestBody user: User): User {
        if (userService.exists(user.username)) {
            throw UserAlreadyExistsException("User with username ${user.username} already exists")
        }
        return userService.create(user)
    }