childrenobjects的MapStruct泛型Map和map组合列表

Question

我有 parent class : User.java 和 2 classes : FacebookUser.java 和 TwitterUser.java 它们是返回的实体取决于数据库中使用 DiscriminatorColumn 的类型列，我想编写正确的映射器来映射可能是 FacebookUser 或 TwitterUser 实例的用户。我有以下映射器似乎无法按预期工作，仅映射 User parent 而不是 children:

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

    User map(UserDTO userDTO);

    @InheritInverseConfiguration
    UserDTO map(User user);

    List<UserDTO> map(List<User> users);

    FacebookUser map(FacebookUserDTO userDTO);

    @InheritInverseConfiguration
    FacebookUserDTO map(FacebookUser user);

    TwitterUser map(TwitterUserDTO userDTO);

    @InheritInverseConfiguration
    TwitterUserDTO map(TwitterUser user);

}

然后我使用：

UserDTO userDto = UserMapper.INSTANCE.map(user);

类映射:

@Entity
@Table(name = "users")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.STRING, length = 10)
@DiscriminatorValue(value = "Local")
public class User {
    @Column
    private String firstName;
    @Column
    private String lastName;
    ///... setters and getters
}

@Entity
@DiscriminatorValue(value = "Facebook")
public class FacebookUser extends User {
    @Column
    private String userId;
    ///... setters and getters
}

@Entity
@DiscriminatorValue(value = "Twitter")
public class TwitterUser extends User {
    @Column
    private String screenName; 
    ///... setters and getters
}

DTO：

public class UserDTO {
    private String firstName;
    private String lastName;
    ///... setters and getters
}

public class FacebookUserDTO extends UserDTO {
    private String userId;
    ///... setters and getters
}

public class TwitterUserDTO extends UserDTO {
    private String screenName; 
    ///... setters and getters
}

此外，如果我有混合了 Facebook 用户和 Twitter 用户或基本用户的用户列表：

假设我有以下用户：

User user = new User ("firstName","lastName");
User fbUser = new FacebookUser ("firstName","lastName","userId");
User twUser = new TwitterUser ("firstName","lastName","screenName");

List<User> users = new ArrayList<>();
users.add(user);
users.add(fbUser);
users.add(twUser);

//Then: 

List<UserDTO> dtos = UserMapper.INSTANCE.map(users);

我只有 firstName 和 lastName 但没有 screenName 或 userId.

有什么解决办法吗？

Answer 1

目前，它似乎还不能作为 mapstruct 的功能使用：Support for Type-Refinement mapping (or Downcast Mapping)

我在他们的 google 组中问了这个问题：https://groups.google.com/forum/?fromgroups#!topic/mapstruct-users/PqB-g1SBTPg

发现我需要在界面内使用 default 方法进行手动映射（对于 java 8）。

还有另一个几乎不适用的映射父对象的问题，所以我又写了一个空 class 父对象 class 的子对象称为 LocalUserDTO：

所以代码变成如下：

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

    LocalUser map(LocalUserDTO userDTO);

    @InheritInverseConfiguration
    LocalUserDTO map(LocalUser user);


    List<UserDTO> map(List<User> users);

    FacebookUser map(FacebookUserDTO userDTO);

    @InheritInverseConfiguration
    FacebookUserDTO map(FacebookUser user);

    TwitterUser map(TwitterUserDTO userDTO);

    @InheritInverseConfiguration
    TwitterUserDTO map(TwitterUser user);

    default UserDTO map(User user) {

        if (user instanceof FacebookUser) {
            return this.map((FacebookUser) user);
        } else if (user instanceof TwitterUser) {
            return this.map((TwitterUser) user);
        } else {
            return this.map((LocalUser) user);
        }
    }

    @InheritInverseConfiguration
    default User map(UserDTO userDTO) {
        if (userDTO instanceof FacebookUserDTO) {
            return this.map((FacebookUserDTO) userDTO);
        } else if (userDTO instanceof TwitterUserDTO) {
            return this.map((TwitterUserDTO) userDTO);
        } else {
            return this.map((LocalUserDTO) userDTO);
        }
    }

}

childrenobjects的MapStruct泛型Map和map组合列表

MapStruct generic Map and map combined list of children objects

java

oop

polymorphism

inheritance

mapstruct