ModelMapper在Java集合类型映射中的挑战与解决方案

import org.modelmapper.ModelMapper;
import org.modelmapper.PropertyMap;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

// 假设 Doctor 和 DoctorDto 类已定义
class Doctor {
    private String name;
    // ... constructors, getters, setters
    public Doctor(String name) { this.name = name; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
}

class DoctorDto {
    private String name;
    // ... constructors, getters, setters
    public DoctorDto(String name) { this.name = name; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
}

// 假设 VetClinic 和 VetClinicDto 类已定义
class VetClinic {
    private List<Doctor> doctors;
    // ... constructors, getters, setters
    public List<Doctor> getDoctors() { return doctors; }
    public void setDoctors(List<Doctor> doctors) { this.doctors = doctors; }
}

class VetClinicDto {
    private List<DoctorDto> doctors; // 注意这里使用 List
    // ... constructors, getters, setters
    public List<DoctorDto> getDoctors() { return doctors; }
    public void setDoctors(List<DoctorDto> doctors) { this.doctors = doctors; }
}

public class ModelMapperListMappingExample {

    public static void main(String[] args) {
        ModelMapper mapper = new ModelMapper();

        // 注册一个 PropertyMap 来处理 VetClinicDto 到 VetClinic 的映射
        mapper.addMappings(new PropertyMap<VetClinicDto, VetClinic>() {
            @Override
            protected void configure() {
                // 跳过默认的 doctors 字段映射，因为 ModelMapper无法直接实例化 List
                skip(destination.getDoctors());

                // 使用 Converter 来手动映射 doctors 列表
                using(context -> {
                    List<DoctorDto> sourceDoctors = (List<DoctorDto>) context.getSource();
                    if (sourceDoctors == null) {
                        return null;
                    }
                    // 遍历源列表，使用 mapper 映射每个 DoctorDto 到 Doctor
                    return sourceDoctors.stream()
                            .map(doctorDto -> mapper.map(doctorDto, Doctor.class))
                            .collect(Collectors.toList());
                }).map(source.getDoctors(), destination.getDoctors());
            }
        });

        // 示例使用
        VetClinicDto vetClinicDto = new VetClinicDto();
        vetClinicDto.setDoctors(new ArrayList<>());
        vetClinicDto.getDoctors().add(new DoctorDto("Dr. Smith"));
        vetClinicDto.getDoctors().add(new DoctorDto("Dr. Jones"));

        VetClinic vetClinic = mapper.map(vetClinicDto, VetClinic.class);

        System.out.println("Mapped VetClinic Doctors:");
        if (vetClinic.getDoctors() != null) {
            vetClinic.getDoctors().forEach(doctor -> System.out.println("- " + doctor.getName()));
        } else {
            System.out.println("No doctors mapped.");
        }
    }
}

<dependencies>
    <!-- 其他依赖 -->
    <dependency>
        <groupId>org.mapstruct</groupId>
        <artifactId>mapstruct</artifactId>
        <version>1.5.5.Final</version> <!-- 使用最新稳定版本 -->
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
                <annotationProcessorPaths>
                    <path>
                        <groupId>org.mapstruct</groupId>
                        <artifactId>mapstruct-processor</artifactId>
                        <version>1.5.5.Final</version>
                    </path>
                    <!-- 如果使用Spring，可能还需要添加Spring相关的processor -->
                    <!-- <path>
                        <groupId>org.springframework.boot</groupId>
                        <artifactId>spring-boot-configuration-processor</artifactId>
                        <version>${spring-boot.version}</version>
                    </path> -->
                </annotationProcessorPaths>
            </configuration>
        </plugin>
    </plugins>
</build>

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

import java.util.List;

// 假设 Doctor, DoctorDto, VetClinic, VetClinicDto 类已定义如前

@Mapper(componentModel = "spring") // 如果在Spring项目中使用，可以设置为"spring"
public interface VetClinicMapper {

    // 获取 Mapper 实例 (如果 componentModel 不是 "spring")
    // VetClinicMapper INSTANCE = Mappers.getMapper(VetClinicMapper.class);

    // 映射 VetClinicDto 到 VetClinic
    VetClinic toVetClinic(VetClinicDto vetClinicDto);

    // 映射 DoctorDto 到 Doctor
    Doctor toDoctor(DoctorDto doctorDto);

    // MapStruct 会自动识别并使用 toDoctor 方法来映射列表中的元素
    // 因此不需要额外的 @Mapping 注解来处理 doctors 列表
    List<Doctor> toDoctorList(List<DoctorDto> doctorDtoList);
}

// 在 Spring 组件中
// @Service
// public class VetClinicService {
//
//     private final VetClinicMapper vetClinicMapper;
//
//     public VetClinicService(VetClinicMapper vetClinicMapper) {
//         this.vetClinicMapper = vetClinicMapper;
//     }
//
//     public VetClinic createVetClinic(VetClinicDto vetClinicDto) {
//         return vetClinicMapper.toVetClinic(vetClinicDto);
//     }
// }

// 或者在非 Spring 环境中直接获取实例
public class MapStructExampleUsage {
    public static void main(String[] args) {
        VetClinicMapper mapper = Mappers.getMapper(VetClinicMapper.class);

        VetClinicDto vetClinicDto = new VetClinicDto();
        vetClinicDto.setDoctors(new ArrayList<>());
        vetClinicDto.getDoctors().add(new DoctorDto("Dr. Smith"));
        vetClinicDto.getDoctors().add(new DoctorDto("Dr. Jones"));

        VetClinic vetClinic = mapper.toVetClinic(vetClinicDto);

        System.out.println("Mapped VetClinic Doctors using MapStruct:");
        if (vetClinic.getDoctors() != null) {
            vetClinic.getDoctors().forEach(doctor -> System.out.println("- " + doctor.getName()));
        } else {
            System.out.println("No doctors mapped.");
        }
    }
}