Java and MapStruct

Question

How i can initialize List in field and add in this list some values?

    @Mapper(componentModel = "spring")
public interface MapStructAdapter {

  @Mapping(source = "some", target = "some")
  @Mapping(expression = "java(new java.util.ArrayList<LegalEntity>())", target = "legalEntities")
  @Mapping(expression = "java(new my.some.package.LegalEntity())", target = "getLegalEntities().add()")
  @Mapping(source = "entityShortName", target = "legalEntities.legalEntity.shortName")
  Representative convert(Message message);
}

bobbroker · Accepted Answer · 2019-11-27 20:27:24Z

1

You should be able to add your own conversion methods in a mapper.

https://mapstruct.org/documentation/stable/reference/html/#adding-custom-methods

Example,

@Mapper(componentModel = "spring")
public interface MapStructAdapter {

    @Mapping(source = "some", target = "some")
    @Mapping(source = "entityShortName", target = "legalEntities")
    Representative convert(Message message);

    default List<LegalEntity> toLegalEntities(String entityShortName) {
        LegalEntity legalEntity = new LegalEntity();
        legalEntity.setShortName(entityShortName);
        return Collections.singletonList(legalEntity);
    }
}

answered Nov 27, 2019 at 20:27

bobbroker

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4 Comments

hc_dev Over a year ago

Very complete answer (includes link to docs and sample code)! Could you explain, how the mapping knows when to use the custom method toLegalEntities. Is there any declaration or naming-convention in place?

Petr Over a year ago

Thank, this is a nice, if i have one field in LegalEntity, but if a have more, then one?

@Mapping(source = "entityShortName", target = "legalEntities.legalEntity.shortName") @Mapping(source = "entityLongName", target = "legalEntities.legalEntity.LongName")

for example

bobbroker Over a year ago

@hc_dev, as far as I understand custom methods take precedence over implicit conversion and MapStruct find is by looking at method argument and return type.

bobbroker Over a year ago

@Petr, that would be easier if you posted the structure of your models. However, it seems a bit too complicated and probably the first you could do is reconsider the structure of your objects. I don't have the answer off the top of my head although I'm pretty sure MapStruct can do this as well.

Sjaak · Accepted Answer · 2019-11-28 06:13:11Z

0

Just add a (factory)method to your mapper. No argument and return the List. Can be a default method or a method in s class you @Mapper#uses

answered Nov 28, 2019 at 6:13

Sjaak

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