How to use modelMapper to convert nested classes

Question

I have a simple class that I want to map to a DTO class using modelMapper.

class Source {

    private String name;
    private String address;
    List<Thing> things;

    // getters and setters follows
    }

    class Thing {

    private String thingCode;
    private String thingDescription;

    // getters and setters
}

and I want to convert these to a sourceDTO that contains a list of ThingDTOs, for example

class sourceDTO {

    private String name;
    private String address;
    List<ThingDTO> things;

    // getters and setters.
    }

     class ThingDTO {

    private String thingCode;
    private String thingDescription;

    // getters and setters
}

If I drop my list of Things and list of ThingsDTO then modelmapper is a delight to use,

 modelMapper.map(source, SourceDTO.class);

But I can't work out how to get the mapper to convert the List of Things to List of ThingDTOs. From the documentation, I think I need to create a mapper class that extends PropertyMap but I can't work out how to configure it.

Any pointers to the relevant documentation would be welcome

Answer 1

I think if you configure your ModelMapper as LOOSE or STANDARD it will do for you.

modelMapper = new ModelMapper();
modelMapper.getConfiguration().setMatchingStrategy(MatchingStrategies.LOOSE);

Otherwhise you could try next:

1. You may create a converter like:

   public class ListThingToThingDTOConverter implements Converter<List<Thing>, List<ThingDTO>> {
   
   
   @Override
   public List<ThingDTO> convert(MappingContext<List<Thing>, List<ThingDTO>> context) {
       List<Thing> source = context.getSource();
       List<ThingDTO> output = new ArrayList<>();
       ...
       //Convert programmatically List<Thing> to List<ThingDTO>
       ...
   
       return output;
     }}
   

2. Then customize a Mapping Thing to ThingDTO as next:

       public class SourceToSourceDTOMap extends PropertyMap<Thing, ThingDTO> {
             @Override
             protected void configure(){
                  using(new ListThingToThingDTOConverter()).map(source.getThings()).setThings(null);
             }
   

3. Finally you must add SourceToSourceDTOMap to your ModelMapper as below:

   modelMapper = new ModelMapper();
   modelMapper.addMappings(new SourceToSourceDTOMap());