Mapstruct mapping - String to List<String>

Question

I am struggling to map a string object from source(Relation.class) and to a List of target(RelationListDTO.class) .

Relation.java

   public class Relation {

    private String name;
    private String email;
    private String completeAddress;

    // getters and setters
}

RelationListDTO.java

public class RelationListDTO {
        private String name;
        private String email;
        private List<Address> address;

        // getters and setters
    }

Address.java

public class Address{
private String street;
private String city;
// getters and setters
}

Mapper class

@Mapper

public interface RelationMapper {

    @Mapping(source = "completeAddress", target = "address.get(0).city")
            RelationListDTO relationToListDto(Relation relation);
}

But it is not working. Could anyone please help.

Filip · Accepted Answer · 2018-11-03 21:05:52Z

7

What you are trying to do using MapStruct is not possible. Because MapStruct doesn't work with run time objects. MapStruct only generated plain java code for mapping two beans. And I find your requirement is little unique. You have a list of Addresses but want to map only city from source object? You can still do like this

@Mapping( target = "address", source = "completeAddress")
RelationListDTO relationToListDto(Relation relation);

// MapStruct will know to use this method to map between a `String` and `List<Address>`
default List<Address> mapAddress(String relation){
      //create new arraylist
      // create new AddressObject and set completeAddress to address.city
     // add that to list and return list

}

edited Nov 3, 2018 at 21:05

Filip

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answered Nov 3, 2018 at 16:21

Naveen

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Comments

Marco Martins · Accepted Answer · 2021-03-08 16:57:20Z

1

Not sure if this was possible at the time of the accepted answer but I had the same problem as you and ended up doing it this way.

@Mapper(imports = Collections.class)
public interface RelationMapper {
    @Mapping(expression = "java(Collections.singletonList(relation.getCompleteAddress()))", target = "address")
            RelationListDTO relationToListDto(Relation relation);
}

answered Mar 8, 2021 at 16:57

Marco Martins

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1 Comment

Ebsan Over a year ago

This is also the preferred way to concat strings as mentioned in github.com/mapstruct/mapstruct/issues/624

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