This commit introduces the following changes.
1) It adds a new Spring @NonNull annotation which allows to apply
@NonNullApi semantic on a specific element, like @Nullable does.
Combined with @Nullable, it allows partial null-safety support when
package granularity is too broad.
2) @Nullable and @NonNull can apply to ElementType.TYPE_USE in order
to be used on generic type arguments (SPR-15942).
3) Annotations does not apply to ElementType.TYPE_PARAMETER anymore
since it is not supported yet (applicability for such use case is
controversial and need to be discussed).
4) @NonNullApi does not apply to ElementType.FIELD anymore since in a
lot of use cases (private, protected) it is not part for the public API
+ its usage should remain opt-in. A dedicated @NonNullFields annotation
has been added in order to set fields default to non-nullable.
5) Updated Javadoc and reference documentation.
Issue: SPR-15756
The main `build.gradle` file contains now only the common build
infrastructure; all module-specific build configurations have
been moved to their own build file.
Issue: SPR-15885
Bean-derived null values may still get passed into bean properties and injection points but only if those are declared as non-required. Note that getBean will never return null; a manual bean.equals(null) / "null".equals(bean.toString()) check identifies expected null values now. This will only ever happen with custom FactoryBeans or factory methods returning null - and since all common cases are handled by autowiring or bean property values in bean definitions, there should be no need to ever manually check for such a null value received from getBean.
Issue: SPR-15829
By using function literals with receiver, we can avoid requiring
lambda parameters for a shorter and nicer syntax. Based on a
proposal from Joseph Taylor.
Issue: SPR-15815
This commit ensure that null-safety is consistent between
getters and setters in order to be able to provide beans
with properties with a common type when type safety is
taken in account like with Kotlin.
It also add a few missing property level @Nullable
annotations.
Issue: SPR-15792
As a follow-up of the ApplicationContext Kotlin extensions, close to
the Kotlin functional WebFlux DSL and partially inspired of the
Groovy/Scala bean configuration DSL, this commit introduces a
lightweight Kotlin DSL for functional bean declaration.
It allows declaring beans as following:
beans {
bean<Foo>()
profile("bar") {
bean<Bar>("bar", scope = Scope.PROTOTYPE)
}
environment({ it.activeProfiles.contains("baz") }) {
bean { Baz(it.ref()) }
bean { Baz(it.ref("bar")) }
}
}
Advantages compared to Regular ApplicationContext API are:
- No exposure of low-level ApplicationContext API
- Focused DSL easier to read, but also easier to write with a fewer
entries in the auto-complete
- Declarative syntax instead of functions with verbs like registerBeans
while still allowing programmatic registration of beans if needed
- Such DSL is idiomatic in Kotlin
- No need to have an ApplicationContext instance to write how you
register your beans since beans { } DSL is conceptually a
Consumer<GenericApplicationContext>
This DSL effectively replaces ApplicationContext Kotlin extensions as
the recommended way to register beans in a functional way with Kotlin.
Issue: SPR-15755
This commits extends nullability declarations to the field level, formalizing the interaction between methods and their underlying fields and therefore avoiding any nullability mismatch.
Issue: SPR-15720
Juergen Hoeller
Sebastien Deleuze
Xavier Downs
Brian Clozel
Stephane Nicoll