未能实例化目标用户的实例。确保用户具有非私有的无参数构造函数-springboot

Question

我正在研究一个springboot应用程序，它公开了一些不返回原始实体的endpoint，但它们返回了它们的DTO。为了映射所有的实体，我使用org.modelmapperversion:2.3.8和project Lombok来避免实现getters、setters和其他一些实用程序。

这些是源实体（我删除了一些属性和Hibernate注释，因为它们在示例中不是必需的）：

user.java

@NoArgsConstructor
@AllArgsConstructor
@ToString
@Getter
@Setter
@Entity(name = "Users")
@ApiModel(description = "All details about user")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "User_Type", discriminatorType= DiscriminatorType.STRING)
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "user_type")
@JsonSubTypes({
        @JsonSubTypes.Type(value = Player.class, name = "player"), //non-abstract subtypes of your abstract class

        @JsonSubTypes.Type(value = Coach.class, name = "coach") })
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;
    private String firstName;   
    private String lastName;    
    private String username;    
    private String email;    
    private String password;   
    private String contactNumber;
}

Player.java

@NoArgsConstructor
@AllArgsConstructor
@ToString
@Getter
@Setter
@Entity(name = "Players")
@DiscriminatorValue(value = "player")
@DiscriminatorOptions(force=true)
public class Player extends User {

    private String dateOfBirth;
    private String notes;
}

Coach.java

@Entity(name = "Coaches")
@DiscriminatorValue(value = "coach")
@DiscriminatorOptions(force=true)
public class Coach extends User{

}

目标DTO为：

userDTo.java

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@ToString
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "User_Type", discriminatorType= DiscriminatorType.STRING)
@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "user_type")
@JsonSubTypes({
        @JsonSubTypes.Type(value = PlayerDto.class, name = "player"), //non-abstract subtypes of your abstract class

        @JsonSubTypes.Type(value = CoachDto.class, name = "coach") })
public abstract class UserDto {

    private String firstName;
    private String lastName;
    private String username;
    private String email;
    private String password;
    private String contactNumber;
    private String dateOfBirth;
    private String notes;
}

PlayerDTo.java

@Getter
@Setter
@AllArgsConstructor
@NoArgsConstructor
@ToString
@DiscriminatorValue(value = "player")
@DiscriminatorOptions(force=true)
public class PlayerDto extends UserDto{

    private String dateOfBirth;
    private String notes;
}

Coach.java

@DiscriminatorValue(value = "coach")
@DiscriminatorOptions(force=true)
public class CoachDto extends UserDto{

}

UserController.java

@PostMapping("/users")
    public void addUsers(@RequestBody List<UserDto> newUsersDto) {
        userService.saveUsers(newUsersDto);
    }

UserService.java

 public void saveUsers(List<UserDto> newUsersDto) {
        List<User> userList = Arrays.asList(modelMapper.map(newUsersDto, User.class));
        userRepository.saveAll(userList);
    }

我试图通过使用Postman发送JSON来创建一个新用户。我正在发送一个用户列表，因为我希望能够一次保存多个用户，并且我正在尝试将其映射为

modelmapper.map（newUsersDto,user.class)

但我得到以下错误：

“ModelMapper映射错误:\n\n1)无法实例化目标com.app.entity.user的实例。请确保com.app.entity.user具有非私有的无参数构造函数。\n\n1错误”

我不知道什么是映射子类的最佳方法。

Answer 1

我不知道Lombok，但基于一个快速的谷歌搜索，添加@noargsconstructor难道不会解决这一点吗？