This commit also removes nullability from two common spots: ResolvableType.getType() and TargetSource.getTarget(), both of which are never effectively null with any regular implementation. For such scenarios, a non-null empty type/target is the cleaner contract.
Issue: SPR-15540
Beyond just formally declaring the current behavior, this revision actually enforces non-null behavior in selected signatures now, not tolerating null values anymore when not explicitly documented. It also changes some utility methods with historic null-in/null-out tolerance towards enforced non-null return values, making them a proper citizen in non-null assignments.
Some issues are left as to-do: in particular a thorough revision of spring-test, and a few tests with unclear failures (ignored as "TODO: NULLABLE") to be sorted out in a follow-up commit.
Issue: SPR-15540
With the new `ParsingPathMatcher` implementation, new patterns are now
allowed, such as `"/foo/{*bar}". The `"{*bar}"` segment will capture
everything until the end of the given path. Adding other elements after
that segment is illegal and will throw exceptions.
One can configure on a `PathMatchConfigurer` various options like
`useTrailingSlashMatch` and `useSuffixPatternMatch`; those options, when
enabled, will try to append suffixes like `".*"` and `"/"` to existing
path patterns. In case of a "capture the rest" pattern segment, those
options won't be honored.
This is why this commit ensures that an exception is thrown at the start
of the application if an illegal configuration is applied to the
`PathMatchConfigurer`.
Issue: SPR-15303, SPR-15558
This commit introduces 2 new @Nullable and @NonNullApi
annotations that leverage JSR 305 (dormant but available via
Findbugs jsr305 dependency and already used by libraries
like OkHttp) meta-annotations to specify explicitly
null-safety of Spring Framework parameters and return values.
In order to avoid adding too much annotations, the
default is set at package level with @NonNullApi and
@Nullable annotations are added when needed at parameter or
return value level. These annotations are intended to be used
on Spring Framework itself but also by other Spring projects.
@Nullable annotations have been introduced based on Javadoc
and search of patterns like "return null;". It is expected that
nullability of Spring Framework API will be polished with
complementary commits.
In practice, this will make the whole Spring Framework API
null-safe for Kotlin projects (when KT-10942 will be fixed)
since Kotlin will be able to leverage these annotations to
know if a parameter or a return value is nullable or not. But
this is also useful for Java developers as well since IntelliJ
IDEA, for example, also understands these annotations to
generate warnings when unsafe nullable usages are detected.
Issue: SPR-15540
Prior to this commit, resolving resources from webjars using the
`WebJarAssetLocator.getFullPath` could lead to multiple candidates,
since this method is trying to find *any* resource matching that path
under the given webjar location.
This commit replaces that call with
`WebJarAssetLocator.getFullPathExact`, which avoids those multiple
matches and only resolves resources if the given path is exact.
Issue: SPR-15526
(cherry picked from commit e2aa117ff9)
Prior to this commit, the AbstractFlashMapManager has used the
originating URI but the query string of the forwarded request. That
resulted to FlashMap not being matched even when both originating
URI and query string matched the FlashMap attributes. The originating
query string is now used to match the forwarded request.
Issue: SPR-15505
HttpMessageConverter's are client and server and arguably shouldn't
contain a server-side concept such a response status.
The status field is recent, it was added to differentiate 400 vs 500
errors with Jackson 2.9+ but there is no need for it since the same
distinction is reflected in raising an HttpMessageNotReadableException
vs a general HttpMessageConversionException.
Issue: SPR-15516
Spring MVC now treats Flux<String> + "application/json" as (serialized)
text to be written directly to the response as is. This is consistent
with the rendering of String + "application/json".
Issue: SPR-15456
