Map OptimisticLockingFailureException to CONFLICT by default

[quaff]

Currently Spring Boot will return INTERNAL_SERVER_ERROR if OptimisticLockingFailureException thrown, It's better to use CONFLICT instead, to archive that I need customize an ExceptionHandler

@ControllerAdvice
@RequiredArgsConstructor
public class GlobalExceptionHandler {

	@ExceptionHandler(OptimisticLockingFailureException.class)
	public void handleConflict(HttpServletRequest request, HttpServletResponse response, Exception e)
			throws IOException {
		response.sendError(HttpStatus.CONFLICT.value());
	}

}

It would be great if Spring Boot handle it by default, or provide a way to map in properties, for example:

server.error.mapping:
   "org.springframework.dao.OptimisticLockingFailureException": 409

[wilkinsona]

Thanks for the suggestions.

It would be great if Spring Boot handle it by default

I don't think we can do this. Any 4xx response indicates that the client is at fault and we can't assume that's the case for every OptimisticLockingFailureException. In some cases it will be a server-side problem and a pessimistic locking strategy should have been used.

Or provide a way to map in properties, for example

This is certainly concise. However, it feels a bit like programming by properties to me and I'm not too sure how generally useful it would be. Let's see what the rest of the team thinks.

[wilkinsona]

The exception to HTTP status mapping part of this is a duplicate of #7349.

[philwebb]

I think I'd prefer not not use properties for Exception -> Status Code mapping since they're not type safe. The HandlerExceptionResolver might already work for general purpose mapping. I think that you can call response.sendError and return a null result.

Since we can't map OptimisticLockingFailureException, and we don't want to add properties support, I think we should close this one and continue the status mapping discussions in #7349.