Motivation and Context

Similar to the recent enhancement in ResolvableType (gh-36545) which introduced ResolvableType.forParameter(Parameter parameter) as a convenience factory method, this PR introduces equivalent parameter-based convenience static factory methods in TypeDescriptor.

Previously, to obtain a TypeDescriptor from a java.lang.reflect.Parameter, developers had to go through MethodParameter.forParameter(parameter) explicitly, which is verbose.

This PR introduces:

• TypeDescriptor.forParameter(Parameter parameter)
• TypeDescriptor.nested(Parameter parameter, int nestingLevel)

Usage Examples (Before vs. After)

Before:

java.lang.reflect.Parameter parameter = method.getParameters()[0];

// Verbose creation of TypeDescriptor via MethodParameter
TypeDescriptor descriptor = new TypeDescriptor(MethodParameter.forParameter(parameter));
TypeDescriptor nestedDescriptor = TypeDescriptor.nested(MethodParameter.forParameter(parameter), 2);

After (New API):

java.lang.reflect.Parameter parameter = method.getParameters()[0];

// Clean and consistent convenience factory methods
TypeDescriptor descriptor = TypeDescriptor.forParameter(parameter);
TypeDescriptor nestedDescriptor = TypeDescriptor.nested(parameter, 2);

Description of Changes

• TypeDescriptor: Added imports for java.lang.reflect.Parameter and implemented the new static factory methods forParameter(Parameter) and nested(Parameter, int).
• TypeDescriptorTests: Added corresponding unit tests:
  • forParameter(): Verifies creation of TypeDescriptor from a valid Parameter.
  • forParameterMustNotBeNull(): Ensures null input triggers an IllegalArgumentException with the correct assertion message.
  • nestedParameter(): Verifies nested type traversal from a Parameter source.
  • nestedParameterMustNotBeNull(): Ensures null input to the nested factory triggers IllegalArgumentException.

Verification Run

All unit tests in the spring-core module have been executed and pass successfully:

./gradlew :spring-core:test --tests "org.springframework.core.convert.TypeDescriptorTests"