将 Jackson Pojo 转换为不同的 Jackson Pojo

Question

I have an input that is a Jackson PoJo and I need to convert it to a different Jackson Pojo. All examples I am finding are from Json -> Pojo and Pojo -> Json. Is creating a custom serializer the way to convert from one Pojo to another?

Answer 1

If the field names match, or have aliases defined, you could simply serialize one object and deserialize into the other; eg

objectMapper.readValue(objectMapper.writeValueAsBytes(object1), Object2.class)

If the fields don't align one-to-one, there isn't a direct way

Therefore, you have some other options

• Copy constructor / Factory method: new Object2(object1) or Object2.from(object1)
• Builder / setter: object2.setX(object1.getX()); // repeat for all fields object2.setX(object1.getX()); // repeat for all fields
• Use a library like ModelMapper (effectively the same as options above)
• Use reflection (very brittle and only to be used if you don't have access to modify either class)

Answer 2

ModelMapper, like OneCricketeer said, or MapStruct can do the job of mapping one POJO to another POJO.

Answer 3

You can use MapStruct like below:

1. Add MapStruct dependency:

    <dependency> <groupId>org.mapstruct</groupId> <artifactId>mapstruct</artifactId> <version>1.4.2.Final</version> </dependency>

Example-

Car.java

public class Car {
    private String make;
    private int seatCount;
    private CarType type;
    //constructor, getters, setters etc.
}

CarDto.java

public class CarDto {
    private String make;
    private int seatCount;
    private String type;
    //constructor, getters, setters etc.
}

CarMapper.java

@Mapper
public interface CarMapper {
 
    CarMapper INSTANCE = Mappers.getMapper( CarMapper.class );
    CarDto carToCarDto(Car car);
    Car carDtoToCar(CarDto carDto);
}

Use:

public void shouldMapCarToDto() {

    Car car = new Car( "Morris", 5, CarType.SEDAN );
    // mapping Car to carDto
    CarDto carDto = CarMapper.INSTANCE.carToCarDto(car);
}

For more details-> MapStruct