How to map a Java Bean using mapstruct library ?

How to map a Java Bean using mapstruct library ?

Five min introduction on mapstruct for Java Bean Mapping.

  1. Why mapping ?
  2. Example Project Setup
  3. How to map using mapstruct annotation ?
  4. Testing
  5. How it works ?
  6. References
  7. Conclusion

This blog, I am going to show a simple example for the understanding on Java Bean Mapping.

Why mapping ?

  • Convert Java Bean/POJO to Another Bean/POJO with different names.
  • Create Report Json with additional calculations.
  • For using DTO Design Pattern.

Example Project Setup

git clone

In this example, we have a Java Bean - Car, we want to convert it to `CarDTO object where it is has different names for mapping.

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How to map using mapstruct annotation ?

Define a mapper interface for above conversion, it will convert Car to CarDto. The mapstruct library generates the implementations for it.

In below interface source:Car, target: CarDto.

// file: ""
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.factory.Mappers;

public interface CarMapper {
    CarMapper INSTANCE = Mappers.getMapper( CarMapper.class );
    @Mapping(target = "seats", source = "seatConfiguration")
    CarDto convert(Car car);

    @Mapping(source = "numberOfSeats", target = "seatCount")
    @Mapping(source = "seatMaterial", target = "material")
    SeatConfigurationDto seatConfigurationToSeatConfigurationDto(SeatConfiguration seatConfiguration);

CarMapper for Converting Car to CarDTO


void testMapping() {
  Car car = new Car();
  car.setSeatConfiguration(new SeatConfiguration(1, SeatMaterial.LEATHER));
  CarDto carDTO = CarMapper.INSTANCE.convert(car);
  assertEquals(car.getMake(), carDTO.getMake());
  assertEquals(car.getType().toString(), carDTO.getType());

How it works ?

  1. If Source and Target bean contains same name, then it will convert directly, for example make is same name in both beans. For all other, you need to define a names using mapping annotation like shown in above.
  2. You need to define another mapping, which will convert the seatConfiguration. For more, refer this section of the blog post


  1. Quick Guide to MapStruct


Using mapstruct, we can easily map Java Beans/POJO using less number of codes. Hope this gives nice introduction, let me know for any doubts here.

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