GenericConverter.getConvertibleTypes returns a pair of Class<?>, while GenericConverter. convert accepts a pair of TypeDescriptor. This is inconsistent because the getConvertibleTypes has no way to specify generic type information that's available in the TypeDescriptor. If I wrote a converter to convert comma-separated string to a list of integers, and another to convert comma-separated string to a list of floats, the getConvertibleTypes wouldn't be able to differentiate between them.
It makes a lot of sense to return a pair of TypeDescriptor from getConvertibleTypes, so that it's consistent with the convert method.
Comment From: jhoeller
getConvertibleTypes is only meant as a basic indication for early filtering. For non-unique cases, you need to implement ConditionalGenericConverter and indicate an actual fit with the intended generics via matches(TypeDescriptor sourceType, TypeDescriptor targetType).