Map multiple fields to one with MapStruct

Question

I have these 3 classes in separate files

public class Book {

   @Id
    @GeneratedValue
    private Long id;

    @NonNull
    private String title;

    @NonNull
    private Author author;

}

public class Author {

    @Id
    @GeneratedValue
    private Long id;

    @NonNull
    private String firstName;

    @NonNull
    private String lastName;

}

public class BookDTO {

    private Long id;

    @NonNull
    private String title;

    @NonNull
    private String author;

}

I have the following mapper

@Mapper
public interface BookMapper { 

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

    @Mappings({
            @Mapping(source = "author.lastName", target = "author")
    })
    BookDTO toDTO(Book book);

}

this currently only maps the lastName and works, and I want to map the author string in Book with

author.firstName + " " + author.lastName

how could I do that? I have not been able to find anything in the MapStruct Documentation.

score 57 · Accepted Answer · answered Oct 09 '18 at 18:14

MapSruct does not support mapping multiple source properties into a single target property.

You have 2 ways to achieve this:

Using Mapping#expression

@Mapping( target = "author", expression = "java(book.getAuthor().getFirstName() + \" \" + book.getAuthor().getLastName())")

Using `@AfterMapping` or `@BeforeMapping`

@Mapper
public interface BookMapper { 

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


    @Mapping(target = "author", ignore = true)
    BookDTO toDTO(Book book);

    @AfterMapping
    default void setBookAuthor(@MappingTarget BookDTO bookDTO, Book book) {
        Author author = book.getAuthor();
        bookDTO.setAuthor(author.getFirstName() + " " + author.getLastName());
    }

}

There is a third way https://stackoverflow.com/a/46309184/1673775 — luke, Nov 16 '20 at 15:27

Edwin M. Cruz · Answer 2 · 2023-06-20T05:41:15.067

4

You can also pass the object referenced by the mapper method containing the multiple fields you need as the source fields to a "qualifiedByName" method by referring to the source using a period.

    @Mapper
    public interface BookMapper { 

       @Mapping(target = "author", source=".", qualifyByName="getFullName")
       BookDTO toDTO(Book book);

       @Named("getFullName")
       String getFullName(Book book) {
           return book.getAuthor().getFirstName() + " " + book.getAuthor().getLastName();
       } 
    }

edited Jun 20 '23 at 05:41

answered May 01 '23 at 02:58

Edwin M. Cruz

362
1
8

Decent solution, but a method within an interface can't be public. This should be `default` – Arie Jun 12 '23 at 12:19

Map multiple fields to one with MapStruct

2 Answers2

Using Mapping#expression

Using `@AfterMapping` or `@BeforeMapping`

Linked

Map multiple fields to one with MapStruct

2 Answers2

Using Mapping#expression

Using @AfterMapping or @BeforeMapping

Linked

Using `@AfterMapping` or `@BeforeMapping`