Prior to this commit, `DispatcherServlet` would completely reset the
response (status, headers and body) before handling errors within Spring
MVC. This can cause unintended consequences when Servlet Filters added
response headers before the error happened. Such response headers might
be still required in case of error handling.
This commit changes the complete reset of the response to only resetting
the response buffer, if possible.
Closes gh-31154
See gh-31104
This is a follow-up change related to gh-31104.
This change reverts the changes previously made in
`ExceptionHandlerExceptionResolver` and instead attempts to reset the
response directly in `DispatcherServlet` in order to cover all types or
exception handling.
Unlike the previous change, we decided to continue even if the response
was already committed: exception handlers will have a chance to be
called, even if it means they'll have to operate on a garbled response.
This change will cause less disruption, in case existing exception
handlers were relying on this behavior.
See gh-31104
Prior to this commit, the `ExceptionHandlerExceptionResolver` would
resolve exceptions and handle them by writing to the HTTP response body,
even if the request was already partially handled and content was
written to the response body.
This could result in HTTP responses with some content for the intended
application response, then other content for the handled exception.
This would happen especially when the error would be raised while
writing to the response (for example when serializing content).
This commit attempts to reset the HTTP response before handling the
exception. This effectively resets the response buffer for the body as
well as response headers. If the response is already committed, the
Servlet container raises an exception and the exception handling is
skipped altogether in order to avoid garbled responses.
Closes gh-31104
Prior to this commit, the `SseEventBuilder` would be used to create SSE
events and write them to the connection using the `ResponseBodyEmitter`.
This would send each data item one by one, effectively writing and
flushing to the network for each. Since multiple data lines are prepared
by the `SseEventBuilder`, a typical write of an SSE event performs
multiple flushes operations.
This commit adds a method on `ResponseBodyEmitter` to perform batch
writes (given a `Set<DataWithMediaType>`) and only flush once all
elements of the set have been written.
This also applies in case of early writes, where now all buffered
elements are written then flushed altogether.
Fixes gh-30912
To handle method validation errors in ResponseEntityExceptionHandler,
MethodValidationException and associated types should not depend on
Bean Validation. To that effect:
1. MethodValidationResult and ParameterValidationResult no longer make
the underlying ConstraintViolation set available, and instead expose
only the adapted validation errors (MessageSourceResolvable, Errors),
analogous to what SpringValidatorAdapter does. And likewise
MethodValidationException no longer extends ConstraintViolationException.
2. MethodValidationPostProcessor has a new property
adaptConstraintViolations to decide whether to simply raise
ConstraintViolationException, or otherwise to adapt the ConstraintViolations
and raise MethodValidationException instead, with the former is the default
for compatibility.
3. As a result, the MethodValidator contract can now expose methods that
return MethodValidationResult, which provided more flexibility for handling,
and it allows MethodValidationAdapter to implement MethodValidator directly.
4. Update Javadoc in method validation classes to reflect this shift, and
use terminology consistent with Spring validation in classes without an
explicit dependency on Bean Validation.
See gh-30644
