MapStruct:如何映射到现有目标？

public class Source {
    private String name;
    private int age;
    // getters and setters
}

public class Target {
    private String name;
    private int age;
    // getters and setters
}

import org.mapstruct.Mapper;
import org.mapstruct.MappingTarget;
import org.mapstruct.factory.Mappers;

@Mapper
public interface Mapper {
    Mapper INSTANCE = Mappers.getMapper(Mapper.class);

    void updateTarget(Source source, @MappingTarget Target target);
}

public class Main {
    public static void main(String[] args) {
        Source source = new Source();
        source.setName("John");
        source.setAge(30);

        Target target = new Target();
        target.setName("Old Name");
        target.setAge(0);

        Mapper.INSTANCE.updateTarget(source, target);

        System.out.println(target.getName()); // 输出: John
        System.out.println(target.getAge());  // 输出: 30
    }
}