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
8379ac772a