Support custom source presence checker expressions for mappings and custom method mappings #2084
Description
Currently mapstruct only allows presence checker methods on the owning source object.
Some types (like java.util.Options, guava Optional, JsonNullable, ...) have presence checker method on the property itself.
With a custom presence checker expression configuration we could write a mapper like:
@Mapper
public interface OptionalMapper {
@SourcePresenceCheckerConfig(
expression = "java( <SOURCE>.<READ_ACCESSOR>() != null && <SOURCE>.<READ_ACCESSOR>().isPresent() )")
default <T> T fromOptional(final Optional<T> optional) {
return optional.orElse(null);
}
// nulls are handled inside method
@SourcePresenceCheckerConfig(nullValueCheckStrategy = NullValueCheckStrategy.NEVER)
default <T> Optional<T> asOptional(final T optional) {
return optional != null ? Optional.of(optional) : Optional.empty();
}
}
or a mapping like:
@Mapping(target = "prop1", source ="prop1", sourcePresenceCheckerExpression = "java( source != null && source.getProp1().isPresent() )")
TargetWithPlainValues asPlain(SourceWithOptional source);
This may address this question:
https://stackoverflow.com/questions/61371019/custom-source-presence-checking-method-name-in-mapstruct
and this issue in a general manner:
#674