一对多关系中FKs引用的JPA复合PK

Question

我正在尝试将下表映射到JPA中。user_tax和税收以及user_tax和用户之间的关系是一对多的。它使我感到困惑，因为我有一个复合主键，我需要将外键映射到这2个键。

错误消息:< code > org . hibernate . annotation exception:mapped by引用未知的目标实体属性:entity。实体中的Tax.user_tax。UserTax.taxs

             tax           user_tax         user
           --------        --------        ------
         PK|t_id  |--------| t_id |PK-FK  |u_name|
           |t_name|   PK-FK| u_id |-------|u_id  | PK
           |      |        | name |       |      |

这是我的实体：

 @Entity
 @Table(name = "user")
 @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
    public class User implements Serializable {

       @Id
       @GeneratedValue(strategy = GenerationType.IDENTITY)
         private Long id;

       @Column(name="u_name")
         private String uname;

          getters + setters
        }

 @Entity
 @Table(name = "tax")
 @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
    public class Tax implements Serializable {

        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
          private Long id;

        @Column(name = "t_name")
          private String tname;

   @Embeddable
    public class UserTaxId implements Serializable {

      @Column(name="u_id")
        private Long uId;

        @Column(name="t_id")
        private Long tId;

  @Entity
  @Table(name = "user_tax")
  @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
    public class UserTax implements Serializable {

      @EmbeddedId
        private UserTaxId userTaxId;

      @OneToMany(fetch = FetchType.LAZY, mappedBy = "user_tax")
        private List<User> users;

      @OneToMany(fetch = FetchType.LAZY, mappedBy = "user_tax")
        private List<Tax> taxs;

Answer 1

我将在这里发布经过3天研究后对我有效的信息。

布赖恩·沃斯伯格正确地发布了用户税务类：

 @Entity
@Table(name = "user_tax")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class UserTax implements Serializable {

    @EmbeddedId
    private UserTaxId userTaxId;

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("uId") // maps uId attribute of embedded id
    private User user;

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("tId") // maps tId attribute of embedded id
    private Tax tax;

    ...
}

然而，我得到了错误消息，我的代码没有编译。然后我还必须编辑用户和税务类：

 @Entity
     @Table(name = "user")
     @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
        public class User implements Serializable {

           @Id
           @GeneratedValue(strategy = GenerationType.IDENTITY)
             private Long id;

           @OneToMany(
            mappedBy = "tid",
            cascade = CascadeType.ALL,
            orphanRemoval = true
        )
        private List<UserTax> tax = new ArrayList<>();

           @Column(name="u_name")
             private String uname;

              getters + setters
            }

    @Entity
     @Table(name = "tax")
     @Inheritance(strategy = InheritanceType.SINGLE_TABLE)
        public class Tax implements Serializable {

            @Id
            @GeneratedValue(strategy = GenerationType.IDENTITY)
              private Long id;

           @OneToMany(
            mappedBy = "uid",
            cascade = CascadeType.ALL,
            orphanRemoval = true
        )
        private List<UserTax> taxs = new ArrayList<>();

            @Column(name = "t_name")
              private String tname;

    setters+getters

    }

以下是我找到问题解决方案的链接:https://vlamihalcea . com/the-best-way-to-map-a-many-to-many-association-with-extra-columns-when-using-JPA-and-hibernate/

Answer 2

您的1： n映射是向后的（即UserTax只能有一个User和一个Tax）并且您正在使用派生标识。尝试像这样映射UserTax：

@Entity
@Table(name = "user_tax")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class UserTax implements Serializable {

    @EmbeddedId
    private UserTaxId userTaxId;

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("uId") // maps uId attribute of embedded id
    private User user;

    @ManyToOne(fetch = FetchType.LAZY)
    @MapsId("tId") // maps tId attribute of embedded id
    private Tax tax;

    ...
}

派生标识在第2.4.1节的JPA 2.2规范中进行了讨论（带有示例）。