Mapstruct check null

Question

I want to check null in method

@Override
public void updateFooFromNonNullAttributesOfDto(FooDto fooDto, Foo foo) {
        if ( fooDto== null ) {
            return;
        }
        if ( fooDto.getBar() != null ) {
            site.setBar( fooDto.getBar() );
        }
         if ( fooDto.getBaz() != null ) {
            site.setBar( fooDto.getBaz() );
        }
}

When I use

@Mapper(NullValueCheckStrategy.ALWAYS)

It's check in all methods, but I want check only in one... How to solve this problem?

Thoracoplasty

May be you can use @Nullable/@NotNull annotations at the method declarations. – Foret

MapStruct does not have support for those annotations yet see #1243 – Condense

The above method looks like a candidate for an @AfterMapping method in the mapper? – Domingo

Answer 1

This is not yet possible with MapStruct, you can either do for all or for none. There is already a feature request for the exact same thing. See 1243

Condense

how to prevent it for all ? No null check at all ? – Annamariaannamarie

That is the default value. NullValueCheckStrategy.ON_IMPLICIT_CONVERSION – Condense

Answer 2

You could annotade your mapping function with a conditionExpression

<i>@Mapping(source="bar", target="bar", conditionExpression = "java(fooDto.getBar()!=null)")</i>

Surroundings

But, that's what MapStruct will do by default .. – Domingo

You are right, so the original question is now the standard behaviour? – Surroundings

Answer 3

You can use some custom Ignore startegy.

Source of discussion :[link][1]

Possible values for ignoreStrategy:

ALWAYS (as true)
NEVER (as false)
NULL_SOURCE (ignore if source value is null) - often required in many projects
    if (source.getValue() != null)
        target.setValue (source.getValue());
NULL_TARGET (ignore if target value is null)
    if (target.getValue() != null)
        target.setValue(source.getValue());

[1]: https://github.com/mapstruct/mapstruct/issues/369 ???

Bug? I can modify the other's answer????

Cleo

I see this article (it's very old), but can't understand how use ignoreStrategy – Thoracoplasty

That part is not implemented yet, it is just a feature request – Condense

Answer 4

According to your example, you give fooDto.getBaz() precedence over fooDto.getBar(). You could realise this in the Mapper-Interface like:

/*
 * regular mapping FooDto.bar to Foo.bar
 */
Foo map(FooDto fooDto);

/*
 * Overwrite Foo.bar by FooDto.baz if present
 */
@AfterMapping
default updateFooFromNonNullAttributesOfDto(FooDto fooDto, Foo foo) {
  if (fooDto== null ) {
    return;
  }
  if(fooDto.getBaz() != null) {
   foo.setBar(fooDto.getBaz());
  }
}

Domingo

Answer 5

In MapStruct, if you want to apply a null value check strategy to only one method instead of all methods, you can use the @Mapping annotation with the nullValueCheckStrategy attribute directly on the method you want to customize. This way, you can specify the null value check strategy for that particular method without affecting other methods in the mapper.

Here's how you can achieve this:

Define Your Mapper:

Annotate your mapper interface with @Mapper without specifying the NullValueCheckStrategy. Use @Mapping on the specific method to apply NullValueCheckStrategy.ALWAYS. Example Implementation:

import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.NullValueCheckStrategy;
import org.mapstruct.factory.Mappers;

@Mapper
public interface FooMapper {

    FooMapper INSTANCE = Mappers.getMapper(FooMapper.class);

    @Mapping(target = "bar", source = "bar", nullValueCheckStrategy = NullValueCheckStrategy.ALWAYS)
  
    void updateFooFromNonNullAttributesOfDto(FooDto fooDto, Foo foo);
}

Amman