Mapstruct 集合映射从相同的源类映射扩展类异常问题—— Ambiguous mapping methods found for mapping collection element

古城微笑少年丶 2022-12-02 01:06 141阅读 0赞

### 问题1：      **票证实体** ###

public class Ticket { private long id; private String title; private Set<Comment> comments; // Getters and setters }

**票证DTO ****（父类）**

public class TicketDTO { private long id; private String title; // Getters and setters }

**带有注释的票证DTO**

public class TicketWithCommentsDTO extends TicketDTO { private List<CommentDTO> comments; // Getters and setters }

**票务映射器界面**

@Mapper(uses= { CommentMapper.class }) public interface TicketMapper { TicketDTO mapToTicketDTO(Ticket ticket); List<TicketDTO> mapToTicketDTOList(Collection<Ticket> tickets); // Adding this method or the last method causes the error TicketWithCommentsDTO mapToTicketWithCommentsDTO(Ticket ticket); List<TicketWithCommentsDTO> MapToTicketWithCommentDTOList(Collection<Ticket> tickets); }

**评论映射器界面**

@Mapper public interface CommentMapper { CommentDTO toCommentDTO(Comment comment); List<CommentDTO> toCommentDTOList(Collection<Comment> comments); }

**引发的错误:**

Ambiguous mapping methods found for mapping collection element to dto.TicketDTO: dto.TicketDTO mapToTicketDTO(model.Ticket ticket), dto.TicketWithCommentsDTO mapToTicketWithCommentsDTO(model.Ticket ticket).

**最佳答案**

这是一个简单的修复，确实是缺少的配置问题。缺少的是`@IterableMapping`批注。

@IterableMapping

将`elementTargetType`设置为正确的类型。  
  
**正确的Mapper代码**

@Mapper(uses = { CommentMapper.class }) public interface TicketMapper { TicketDTO mapToTicketDTO(Ticket ticket); @IterableMapping(elementTargetType = TicketDTO.class) List<TicketDTO> mapToTicketDTOList(Collection<Ticket> tickets); TicketWithCommentsDTO mapToTicketWithCommentsDTO(Ticket ticket); @IterableMapping(elementTargetType = TicketWithCommentsDTO.class) List<TicketWithCommentsDTO> mapToTicketWithCommentDTOList(Collection<Ticket> tickets); }

========================

### 问题2： 多集合Mapping异常 BaseDO 为父类 ###

/**
         * dtoToDO
         *
         * @param dto
         * @return
         */
        ObjectControlDO dtoToDO(ObjectControlDto dto);
    
        /**
         * dtosToDOs
         *
         * @param dtos
         * @return
         */
        List<ObjectControlDO> dtosToDOs(List<ObjectControlDto> dtos);
    
        /**
         * dtoToDO
         *
         * @param dto
         * @return
         */
        BaseDO dtoToBaseDO(ObjectControlDto dto);
    
        /**
         * dtosToDOs
         *
         * @param dtos
         * @return
         */
        List<BaseDO> dtosToBaseDOs(List<ObjectControlDto> dtos);

解决方式

/**
         * dtoToDO
         *
         * @param dto
         * @return
         */
        @Named(value = "dtoToDO")
        ObjectControlDO dtoToDO(ObjectControlDto dto);
    
        /**
         * dtosToDOs
         *
         * @param dtos
         * @return
         */
        @IterableMapping(qualifiedByName = "dtoToDO")
        List<ObjectControlDO> dtosToDOs(List<ObjectControlDto> dtos);
    
        /**
         * dtoToDO
         *
         * @param dto
         * @return
         */
        @Named(value = "dtoToBaseDO")
        BaseDO dtoToBaseDO(ObjectControlDto dto);
    
        /**
         * dtosToDOs
         *
         * @param dtos
         * @return
         */
        @IterableMapping(qualifiedByName = "dtoToBaseDO")
        List<BaseDO> dtosToBaseDOs(List<ObjectControlDto> dtos);

### 3、 mapstruct-将父字段值传播给嵌套对象的集合 ###

可以将值从父对象传播到嵌套对象的集合

**DTO源类**

class CarDTO {
      private String name;
      private long userId;
      private Set<WheelDto> wheels; 
    };
    
    class WheelDto {
      private String name;
    }

**目标实体类**

class Car {
      private String name;
      private long userId;
      private Set<Wheel> wheels; 
    };
    
    class Wheel {
      private String name;
      private long lastUserId;
    }

如您所见，我在WheelDto上没有lastUserId，因此我想在wheel集合中的每个对象上将CarDto的userId映射到WheelDto的lastUserId。

**最佳答案**

当前无法传递属性。但是，您可以通过`@AfterMapping`和/或`@Context`解决此问题。  
  
汽车映射后更新车轮  
  
但是，这意味着您需要对`Wheel`进行两次迭代。它看起来像

@Mapper public interface CarMapper { Car map(CarDto carDto); @AfterMapping default void afterCarMapping(@MappingTarget Car car, CarDto carDto) { car.getWheels().forEach(wheel -> wheel.setLastUserId(carDto.getUserId())); } }

在映射轮时传递@Context以便在映射期间具有状态  
  
如果您只想通过`Wheel`进行一次迭代，则可以传递一个`@Context`对象，该对象将在映射汽车之前从`CarDto`获取userId，然后在之后的映射中将其设置在`Wheel`上。该映射器如下所示:

@Mapper public interface CarMapper { Car map(CarDto carDto, @Context CarContext context); Wheel map(WheelDto wheelDto, @Context CarContext context); } public class CarContext { private String lastUserId; @BeforeMapping public void beforeCarMapping(CarDto carDto) { this.lastUserId = carDto.getUserId(); } @AfterMapping public void afterWheelMapping(@MappingTarget Wheel wheel) { wheel.setLastUserId(lastUserId); } }

`CarContext`将传递到车轮映射方法。

### Mapstruct-从多个集合映射到单个集合 ###

使用MapStruct，我的源对象中有两个集合，其中包含略有不同的对象。我想将这两个集合的对象映射为通用类型，然后将它们全部插入单个集合中。类似于以下内容：

List<UserNumber> listsToDtoList(List<PhoneNumber> phoneNumbers, List<FaxNumber> faxNumbers); UserNumber phoneToPhoneDto(PhoneNumber phone); UserNumber faxToPhoneDto(FaxNumber fax);

使用MapStruct做到这一点的最简单方法是什么？

**最佳答案**

因此，我将根据我的`SourceObject`进行映射（不写`List<UserNumber> listsToDtoList(List<PhoneNumber> phoneNumbers, List<FaxNumber> faxNumbers);`  
  
所以大致如下：

@Mapping( target = "userNumbers", source = "phoneNumbers" ) Target map( Source source ); @AfterMapping // will be applied in the final part of the previous method default void map ( Source source, @MappingTarget Target target ) { target.getUserNumbers().addAll(source.getFaxNumbers()); }

参照：

[https://mapstruct.org/documentation/stable/reference/html/][https_mapstruct.org_documentation_stable_reference_html]

[https_mapstruct.org_documentation_stable_reference_html]: https://mapstruct.org/documentation/stable/reference/html/