Mapstruct映射多对一空结果

Question

Mapstruct在Spring-Boot rest api中使用一对多和多对一关系映射我的实体时遇到了一个问题。

我有下面的课

Policy.class

@Data
@Entity
@Table(name = "Policy")
public class Policy implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "Policy_UID", nullable = false)
    private Integer policyUid;

    //other fields without relationships

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "userID", referencedColumnName = "Id")
    private User user;
}


User.class

@Data
@Entity
@Table(name = "User")
public class User implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @Column(name = "Id")
    private Integer id;

    //other fields without relationships

    @OneToMany(mappedBy = "user")
    @JsonIgnore
    public List<Policy> policyList;
}



PolicyDTO.class

@Data
@AllArgsConstructor
@NoArgsConstructor
public class PolicyDTO {

    private Integer policyUid;

    //other fields without relationships

    private UserDTO user;
}

UserDTO.class

@Data
@AllArgsConstructor
@NoArgsConstructor
public class UserDTO {

    private Integer id;

    //other fields without relationships

    public List<PolicyDTO> policyList;
}


PolicyMapper.class

@Mapper (componentModel = "spring")
public interface PolicyMapper {
    PolicyDTO policytoPolicyDTO(Policy policy);
    List<PolicyDTO> toPolicyListDTO(List<Policy> policies);
}

UserMapper.class

@Mapper(componentModel = "spring")
public interface UserMapper {
    UserDTO toUserDTO(User user);
    List<UserDTO> toUserListDTO(List<User> UsersList);
}

and the calling for results

List<PolicyDTO> list = policyMapper.toPolicyListDTO(paging.getContent());
return new PageImpl<>(list, page, paging.getTotalElements());

因此，当我在评论中添加私有UserDTO用户时；进入PolicyDTO和公共列表PolicyList；进入UserDTO

结果策略列出了所有字段中的值都可以，当然，除了两个注释字段。如果我用双向关系将这两个字段取消注释到DTO中，结果不仅在关系字段中是null，而且在所有字段中都是null。所有字段都是空的，就像所有行为都没有结果一样。

Answer 1

首先，尝试使用MapStruct版本

<mapstruct.version>1.3.1.Final</mapstruct.version>

要用spring实现MapStruct，您应该创建一个接口EntityMapper，其中包含两个泛型参数 ，并编写以下方法：

public interface EntityMapper <D, E> {

    public E toEntity(D dto);

    public D toDto(E entity);

    public List<E> toEntity(List<D> dtoList);

    public List <D> toDto(List<E> entityList);
}

并创建自己的实体接口

@Mapper(componentModel = "spring", uses = {})
public interface PolicyMapper extends EntityMapper<PolicyDTO, Policy> {
    PolicyDTO toDto(Policy policy);

    Policy toEntity(PolicyDTO policyDTO);

    default Policy fromId(Long id) {
        if (id == null) {
            return null;
        }
        Policy policy = new Policy();
        policy.setId(id);
        return policy;
    }
}

@Mapper(componentModel = "spring", uses = {})
public interface UserMapper extends EntityMapper<UserDTO, User> {
    UserDTO toDto(User user);

    User toEntity(UserDTO userDTO);

    default User fromId(Long id) {
        if (id == null) {
            return null;
        }
        User user = new User();
        user.setId(id);
        return user;
    }
}

您不需要定义一个方法来呈现列表，这是MapStruct的一个功能，可以映射实体中的所有字段，您只需要toDto，toEntity，就可以了。

我希望这对你有帮助；）