MapStruct

官网： https://mapstruct.org/

expression 来指定一个 Java 表达式

@Mapper
public interface CarMapper {

    @Mapping(target = "make", source = "make")
    @Mapping(target = "seatCount", source = "numberOfSeats")
    @Mapping(target = "manufacturingDate", expression = "java(new java.text.SimpleDateFormat(\"yyyy-MM-dd\").format(car.getManufacturingDate()))")
    CarDto carToCarDto(Car car);
}

自定义方法

@Mapper
public interface CarMapper {

    @Mapping(target = "make", source = "make")
    @Mapping(target = "seatCount", source = "numberOfSeats")
    @Mapping(target = "manufacturingDate", source = "manufacturingDate", dateFormat = "yyyy-MM-dd")
    @Mapping(target = "type", source = "type", qualifiedByName = "typeToTypeDto")
    CarDto carToCarDto(Car car);

    @Named("typeToTypeDto")
    default String typeToTypeDto(Type type) {
        return type != null ? type.getDescription() : null;
    }
}

使用 @AfterMapping 和 @BeforeMapping

@Mapper
public interface CarMapper {

    @Mapping(target = "make", source = "make")
    CarDto carToCarDto(Car car);

    @AfterMapping
    default void setAdditionalData(@MappingTarget CarDto carDto, Car car) {
        carDto.setAdditionalInfo("Processed on: " + LocalDate.now());
    }
}

使用装饰器设计模式

@Mapper(uses = CarMapperDecorator.class)
public interface CarMapper {

    @Mapping(target = "make", source = "make")
    CarDto carToCarDto(Car car);
}

public abstract class CarMapperDecorator implements CarMapper {
    private final CarMapper delegate;

    public CarMapperDecorator(CarMapper delegate) {
        this.delegate = delegate;
    }

    @Override
    public CarDto carToCarDto(Car car) {
        CarDto dto = delegate.carToCarDto(car);
        // 添加额外的逻辑
        dto.setExtraField("Value");
        return dto;
    }
}

source 对象的多个属性转为 target 对象的一个属性

XxxVO toVOSimply(XxxEntity entity);

@IterableMapping(qualifiedByName = "toVO")
List<XxxVO> toVO(List<XxxEntity> entity);

@Named("toVO")
default XxxVO toVO(XxxEntity entity) {
    XxxVO vo = toVOSimply(entity);
    // 自定义多个属性转一个属性逻辑
    vo.setConnection(ArrayUtil.join(new String[]{vo.getConnectionType1(),
                    vo.getConnectionType2(),
                    vo.getConnectionType3()},
            ","));
    return vo;
}