This commit brings back the writeHeaders method on ServerHttpResponse
that was once added (2a6a4f) and then removed (9c7151).
This version is a little simpler since writeHeaders doesn't explicitly
flush/send headers which runtimes are expected to do by default.
Instead the main purpose of writeHeaders now is to ensure changes made
via HttpHeaders are applied to the underlying runtime response at some
point and we now do that once at the very end.
This approach provides the most flexibility (vs keeping HttpHeaders in
sync) because it allows a full and consistent set of mutative
operations for both headers and cookies (to be added) regardless of the
API exposed by the underlying runtime.
This change adds a WebServerExchange and updates all contracts at the
the same level (i.e. org.springframework.web.server) as well as the
org.springframework.web.reactive level to use it so that all
framework-related code will have access to server-side processing
features such as request attributes (and others to come).
This change separates out lower-level HTTP adapter code from the more
(framework-specific) HTTP processing into a separate package under
org.springframework.web.server (not under org.springframework.http).
Flux and Mono are used both for implementation and exposed at API
level to express 1 versus N semantic and to provide default Rx
operators:
- Flux<T> for multiple values Publisher (issue #48)
- Mono<T> for single value Publisher (issue #50)
- Mono<Void> for Publisher with no value (issue #49)
For those runtimes that don't directly support Reacitve Streams this
commit separates more formally Reactive Streams bridge code out of
the request and response implementations which become simple adapters
to the ServerHttpRequest/Response contracts like their RxNetty and
Reactor Net counterparts.
ServerHttpResponse implementations now immediately propagate
HttpHeaders changes as they so there is no need to call applyHeaders().
The writeHeaders from ServerHttpResponse is also removed. RxNetty and
Reactor Net both support implicitly completing if the handler
completes without explicitly writing the headers or the response body.
The DispatcherHandler now has an errorMapper property that is a
function for transforming errors. By default this property is set to an
instance of DispatcherHandlerExceptionMapper which wraps "standard"
framework exceptions and @ResponseStatus-annotated exceptions as
ResponseStatusException.
This makes it easy to handle the exceptions downstream uniformly.
This change adds a ResponseStatusException to associate an exception
with a status code at runtime. Along with that is an
ResponseStatusExceptionHandler that handles ResponseStatusException
by setting the response status.
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.
Rossen Stoyanchev
Stephane Maldini
Sebastien Deleuze