This commit handles "empty" cases for `ResponseEntity` controller
handler return types when wrapped with a `java.util.Optional` in Spring
MVC or a single `Publisher` like `Mono`.
Given the following example for Spring MVC:
```
@GetMapping("/user")
public Optional<ResponseEntity<User>> fetchUser() {
Optional<User> user = //...
return user.map(ResponseEntity::ok);
}
```
If the resulting `Optional` is empty, Spring MVC will infer a
`ResponseEntity` with an empty body and a 404 HTTP response status.
The same reasoning is applied to Spring WebFlux with Publisher types:
```
@GetMapping("/user")
public Mono<ResponseEntity<User>> fetchUser() {
Mono<User> user = //...
return user.map(ResponseEntity::ok);
}
```
This feature is only valid for `HttpEntity` return types and does not
apply to `@ResponseBody` controller handlers.
Issue: SPR-13281
Forwarded headers are now processed before ServerWebExchange is created
through ForwardedHeaderTransformer which has the same logic as the
ForwardedHeaderFilter but works on the request only.
ForwardedHeaderFilter is deprecated as of 5.1 but if registered it is
removed from the list of filters and ForwardedHeaderTransformer is used
instead.
Issue: SPR-17072
This commit introduces Protobuf support in WebFlux via dedicated
codecs.
Flux<Message> are serialized/deserialized using delimited Protobuf
messages with the size of each message specified before the message
itself. In that case, a "delimited=true" parameter is added to the
content type.
Mono<Message> are expected to use regular Protobuf message
format (without the size prepended before the message).
Related HttpMessageReader/Writer are automatically registered when the
"com.google.protobuf:protobuf-java" library is detected in the classpath,
and can be customized easily if needed via CodecConfigurer, for example
to specify protocol extensions via the ExtensionRegistry based
constructors.
Both "application/x-protobuf" and "application/octet-stream" mime types
are supported.
Issue: SPR-15776
The new EncodedResourceResolver is a generalized version of
GzipResourceResolver that can be configured to support different
content codings, by "br" and "gzip".
GzipResourceResolver is now deprecated.
Issue: SPR-16381
This commit removes all places where forwarded headers are checked
implicitly, on an ad-hoc basis.
ForwardedHeaderFilter is expected to be used instead providing
centralized control over using or discarding such headers.
Issue: SPR-16668
@EnableWebFlux bootstraps both annotated controllers and functional
endpoints, so we need to be more explicit about which parts of the
configuration apply to which.
Issue: SPR-16360
Sam Brannen
Brian Clozel
Rossen Stoyanchev
sdeleuze
Violeta Georgieva
Juergen Hoeller
Jeremy Wright
Daniel Kift
KwonJH
Johnny Lim
Jan Nielsen