MapStruct use nested mapper based on input parameters - mapstruct

Question

in this simple scenario I have a Pen that have a Color. I want to map the color of a pen using a nested mapper method instead of another, based on a variable input in the Pen mapper.
Color entity:
public class ColorEntity {
private Long colorId;
private String colorName;
}
Pen entity:
public class PenEntity {
private Long penId;
private String penArticle;
private ColorEntity color;
}
Color DTO:
public class ColorDTO {
private Long colorId;
private String colorName;
}
Pen DTO:
public class PenDTO {
private Long penId;
private String penArticle;
private ColorDTO color;
}
Color mapper: if I call ColorMapper.toDto(color, locale) the second method should be used.
#Mapper(componentModel = "spring")
public interface ColorMapper {
ColorDTO toDto(ColorEntity colorEntity);
default ColorDTO toDto(ColorEntity colorEntity, Locale locale) {
ColorDTO colorDTO = toDto(colorEntity);
if(locale.equals(Locale.ITALIAN)) {
colorDTO.setColorName("ROSSO");
}
else {
colorDTO.setColorName("Language not supported");
}
return colorDTO;
}
}
Pen mapper: same of ColorMapper, if I call PenMapper.toDto(pen, locale) the second method should be used.
#Mapper(componentModel = "spring", uses = {ColorMapper.class})
public interface PenMapper {
PenDTO toDto(PenEntity penEntity);
PenDTO toDto(PenEntity penEntity, Locale locale);
}
The problem is that in the generated PenMapperImpl, the method public PenDTO toDto(PenEntity penEntity, Locale locale) doesn't use the method ColorMapper.toDto(color, locale) to translate the color.
#Generated(
value = "org.mapstruct.ap.MappingProcessor",
date = "2021-04-21T17:33:22+0200",
comments = "version: 1.4.2.Final, compiler: Eclipse JDT (IDE) 1.3.1200.v20200916-0645, environment: Java 15.0.2 (Oracle Corporation)"
)
#Component
public class PenMapperImpl implements PenMapper {
#Autowired
private ColorMapper colorMapper;
#Override
public PenDTO toDto(PenEntity penEntity) {
if ( penEntity == null ) {
return null;
}
PenDTO penDTO = new PenDTO();
penDTO.setColor( colorMapper.toDto( penEntity.getColor() ) );
penDTO.setPenArticle( penEntity.getPenArticle() );
penDTO.setPenId( penEntity.getPenId() );
return penDTO;
}
#Override
public PenDTO toDto(PenEntity penEntity, Locale locale) {
if ( penEntity == null && locale == null ) {
return null;
}
PenDTO penDTO = new PenDTO();
if ( penEntity != null ) {
// HERE SHOULD BE GENERATED THE
// penDTO.setColor( colorMapper.toDto( penEntity.getColor() , locale ) );
penDTO.setColor( colorMapper.toDto( penEntity.getColor() ) );
penDTO.setPenArticle( penEntity.getPenArticle() );
penDTO.setPenId( penEntity.getPenId() );
}
return penDTO;
}
}
How can I resolve this? I'm looking for a general solution (not puntual for this case) because I have a lot of this same situations in a project.
Thanks and regards

Answer 1

MapStruct does not use the input parameters when looking for methods in other mappers.
In order to achieve this you'll need to give some help to MapStruct.
The way to do this would be to use #Context. Using that MapStruct will propagate that to other mappers.
So in your case it will look something like:
#Mapper(componentModel = "spring")
public interface ColorMapper {
ColorDTO toDto(ColorEntity colorEntity);
default ColorDTO toDto(ColorEntity colorEntity, #Context Locale locale) {
ColorDTO colorDTO = toDto(colorEntity);
if(locale.equals(Locale.ITALIAN)) {
colorDTO.setColorName("ROSSO");
}
else {
colorDTO.setColorName("Language not supported");
}
return colorDTO;
}
}
#Mapper(componentModel = "spring", uses = {ColorMapper.class})
public interface PenMapper {
PenDTO toDto(PenEntity penEntity);
PenDTO toDto(PenEntity penEntity, #Context Locale locale);
}
This way when using the toDto with the Locale context MapStruct will choose the ColorMapper#toDto with the Locale.