We have had an ObjectToOptionalConverter since Spring Framework 4.1;
however, prior to this commit we did not have a standard Converter for
the inverse (Optional to Object).
To address that, this commit introduces an OptionalToObjectConverter
that unwraps an Optional, using the ConversionService to convert the
object contained in the Optional (potentially null) to the target type.
This allows for conversions such as the following.
- Optional.empty() -> null
- Optional.of(42) with Integer target -> 42
- Optional.of(42) with String target -> "42"
- Optional.of(42) with Optional<String> target -> Optional.of("42")
The OptionalToObjectConverter is also registered by default in
DefaultConversionService, alongside the existing
ObjectToOptionalConverter.
See gh-20433
Closes gh-34544
This commit removes the BDDMockito Checkstyle rule, since it did not
actually enforce the use of BDDMockito.
This commit also updates static imports to use Mockito instead of
BDDMockito where appropriate (automated via the Eclipse IDE Organize
Imports clean-up task).
Closes gh-34616
This commit introduces null-safe support for java.util.Optional in the
following SpEL operators:
- PropertyOrFieldReference
- MethodReference
- Indexer
- Projection
- Selection
- Elvis
Specifically, when a null-safe operator is applied to an empty
`Optional`, it will be treated as if the `Optional` were `null`, and
the subsequent operation will evaluate to `null`. However, if a
null-safe operator is applied to a non-empty `Optional`, the subsequent
operation will be applied to the object contained in the `Optional`,
thereby effectively unwrapping the `Optional`.
For example, if `user` is of type `Optional<User>`, the expression
`user?.name` will evaluate to `null` if `user` is either `null` or an
empty `Optional` and will otherwise evaluate to the `name` of the
`user`, effectively `user.get().getName()` for property access.
Note, however, that invocations of methods defined in the `Optional`
API are still supported on an empty `Optional`. For example, if `name`
is of type `Optional<String>`, the expression `name?.orElse('Unknown')`
will evaluate to "Unknown" if `name` is an empty `Optional` and will
otherwise evaluate to the `String` contained in the `Optional` if
`name` is a non-empty `Optional`, effectively `name.get()`.
Closes gh-20433
Prior to this commit, if an appropriate Converter was registered with
the ConversionService that converts from a POJO to an array and that
ConversionService was registered with the Spring Expression Language
(SpEL) TypeConverter, an attempt to invoke a varargs method in a SpEL
expression with such a POJO would fail because the ConversionService
was not used to convert the POJO to an array suitable for the varargs
method invocation.
This commit revises the implementations of convertArguments(...) and
convertAllMethodHandleArguments(...) in ReflectionHelper to support
such use cases.
Closes gh-34371
This commit refines KotlinDetector usages and implementation in order
to remove preliminary KotlinDetector#isKotlinReflectPresent invocations
and to ensure that KotlinDetector methods are implemented safely and
efficiently for such use case.
Closes gh-34275
This commit updates the whole Spring Framework codebase to use JSpecify
annotations instead of Spring null-safety annotations with JSR 305
semantics.
JSpecify provides signficant enhancements such as properly defined
specifications, a canonical dependency with no split-package issue,
better tooling, better Kotlin integration and the capability to specify
generic type, array and varargs element null-safety. Generic type
null-safety is not defined by this commit yet and will be specified
later.
A key difference is that Spring null-safety annotations, following
JSR 305 semantics, apply to fields, parameters and return values,
while JSpecify annotations apply to type usages. That's why this
commit moves nullability annotations closer to the type for fields
and return values.
See gh-28797
Prior to this commit, if a MethodHandle was registered as a custom
function in the Spring Expression Language (SpEL) for a static method
that accepted only a variable argument list (for example,
`static String func(String... args)`), attempting to invoke the
registered function within a SpEL expression resulted in a
ClassCastException because the varargs array was unnecessarily wrapped
in an Object[].
This commit modifies the logic in FunctionReference's internal
executeFunctionViaMethodHandle() method to address that.
Closes gh-34109
Prior to this commit, the SpEL Tokenizer threw an IllegalStateException
when an unsupported character was detected in a SpEL expression;
however, the Javadoc for ExpressionParser.parseExpression() states that
it throws a ParseException if an exception occurred during parsing.
This commit addresses that issue by throwing a SpelParseException for
an unsupported character in a SpEL expression, using a new
UNSUPPORTED_CHARACTER enum constant in SpelMessage.
Closes gh-33767
