General improvements e.g. make use of Java 8 Stream. The main reason
for the refactoring however to tighten error handling. To that extent:
InvocableHandlerMethod turns all exceptions into Reactive Streams
error signals, in effect never allowing any Exceptions to bubble up.
HandlerMethodArgumentResolver may throw an Exception for sync resolution
or produce an error signal via the returned Publisher. Either way the
exception is consistently wrapped with helpful method argument details.
For the latter case using a custom mapError operator.
HandlerMethodArgumentResolver no longer needs to return Optional for
nullable argument values. Instead (for now) the defaultIfEmpty operator
of reactor.rx.Stream operator is used to ensure a default constant value
(called "NO_VALUE") is produced. That way an argument resolver may
produce 0..1 values where 0 means it did not resolve to any value and
that results in null passed as the argument value.
If a HandlerMethodArgumentResolver produces more than one value, all
additional values beyond the first one will be ignored with the help
of a custom "first" operator.
As HandlerMethod is invoked within the map operator, checked exceptions
are not allowed but instead of wrapping it in a runtime exception what
we really need is to unwrap the target exception for exception
resolution purposes. To this end concatMap is used to produce a nested
Publisher or an error Publisher with the unwrapped target exception.
Related to that InvocableHandlerMethod now returns
Publisher<HandlerResult> instead of Publisher<Object> so that no longer
needs to be externally mapped from Object to HandlerResult.
InvocableHandlerMethodTests provides tests for the above scenarios and
verifies the details of resulting error signals.
This change also removes reactor-stream variants of the request and
response since the request and response aren't used directly by
application code and get passed through reactor.Publishers anyway.
Fixed a bug where the URL content negotiation "format" parameter values
were case sensitive and only lowercase values were accepted. For
example, URL query parameter format=json returned the appropriate JSON
response but format=JSON resulted in a
HttpMediaTypeNotAcceptableException and returned:
406 - The resource identified by this request is only capable of
generating responses with characteristics not acceptable according to
the request "accept" headers.
When the MappingMediaTypeFileExtensionResolver is constructed, it is
passed a map containing the media type key to MediaType mappings
defined in the ContentNegotiationConfigurer. In the constructor of
MappingMediaTypeFileExtensionResolver, the keys are converted to
lowercase and the mappings of keys to MediaTypes are added to the
ConcurrentMap<String, MediaType> mediaTypes using the lowercase
version of the keys. However, when retrieving the MediaType from a key
in the lookupMediaType method, no conversion to lowercase is performed
so any value for the URL "format" parameter other than the lowercase
version will not return the proper MediaType result.
On May 1st, 2014, a change was made to
ParameterContentNegotiationStrategy to handle cases where the content
negotiation format URL parameter does not result in a match for a
MediaType. If no match is found, a HttpMediaTypeNotAcceptableException
is thrown resulting in the 406 response above. Prior to this commit, a
null was returned instead of throwing an exception so this issue was
hidden and appeared to function correctly.
To make the media type lookup case insensitive, added a line to the
lookupMediaType method in MediaTypeFileExtensionResolver to first
convert the extension (media type key) to lowercase prior to attempting
to retrieve it from the mediaTypes map.
Issue: SPR-13747
This commit reworks the arrangement to a centralized cache, avoiding any extra reflection attempts if a cache entry is known already. In the course of this, it also enforces toXXX methods to be declared as non-static now (which is the only sensible arrangement anyway).
Issue: SPR-13703
