Java 使Hibernate实体中的主键与外键相同_Java_Mysql_Hibernate_Jpa

Java 使Hibernate实体中的主键与外键相同

java mysql hibernate jpa

Java 使Hibernate实体中的主键与外键相同,java,mysql,hibernate,jpa,Java,Mysql,Hibernate,Jpa,我刚开始冬眠。我在以下两个实体工作：实体1如下所示： @Entity @Table(name = "vm_user") public class VmUser implements Serializable { private static final long serialVersionUID = 1L; @Column(name = "created_by") private String createdBy; @Column(name = "last

我刚开始冬眠。我在以下两个实体工作：

实体1如下所示：

@Entity
@Table(name = "vm_user")
public class VmUser implements Serializable {

    private static final long serialVersionUID = 1L;

    @Column(name = "created_by")
    private String createdBy;

    @Column(name = "last_modified_by")
    private String lastModifiedBy;

    @Column(name = "created_date")
    private Instant createdDate;

    @Column(name = "last_modified_date")
    private Instant lastModifiedDate;

    @OneToOne
    @JoinColumn(unique = true)
    private User user;             <--- HOW WILL I DENOTE THIS PRIMARY KEY OF VMUSER ENTITY ?

@Entity
@Table(name = "my_entity")
public class MyEntity implements Serializable {

    private static final long serialVersionUID = 1L;

    @Column(name = "created_by")
    private String createdBy;

    @Column(name = "last_modified_by")
    private String lastModifiedBy;

    @Column(name = "created_date")
    private Instant createdDate;

    @Column(name = "last_modified_date")
    private Instant lastModifiedDate;

    @ManyToOne
    private A a;

    @OneToOne
    @JoinColumn(unique = true)
    private B b;

在mysql中的关联表中，即

my_entity

，主键是a的

id

和b的

id

的组合。我不知道如何在Hibernate实体

MyEntity

中表示这一点

关于这一点，我已经看了一些帖子：和，但不知道如何做这两个？

解决方案是

@MapsId

比如说

@Entity
@Table(name = "vm_user")
public class VmUser implements Serializable {

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

    @MapsId
    @OneToOne
    private User user;

您还可以删除

@JoinColumn（unique=true）

，因为

@Id

已经使其唯一

public class MyEntityPk implements Serializable {

   private Integer aId;
   private Integer bId;

   // IMPORTANT: Override equals() and hashCode()
}


@IdClass(MyEntityPk.class)
@Entity
@Table(name = "my_entity")
public class MyEntity implements Serializable {

    @Id
    private Integer aId;
    @Id
    private Integer bId;

    @MapsId("aId")
    @ManyToOne
    private A a;

    @MapsId("bId")
    @OneToOne
    private B b;

请在Hibernate文档中找到更多信息，您需要使用

@EmbeddedId

和

@MapsId

@Entity
@Table(name = "vm_user")
public class VmUser implements Serializable {
   @Id
    @Column(name = "user_id")    
    private Integer id;

    @MapsId("user_id")
    @OneToOne
    private User user;  
}

你可以为MyEntity做如下相同的事情

@Embeddable
class BKey {
  private int aId;
  private int bId;
}


@Entity
@Table(name = "my_entity")
public class MyEntity implements Serializable {

    @EmbeddedId
    private BKey primaryKey;

    @MapsId("aId")
    @ManyToOne
    private A a;

    @MapsId("bId")
    @OneToOne
    @JoinColumn(unique = true)
    private B b;
}

VM用户类

public class VmUser implements Serializable {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@OneToOne
@JoinColumn(name="ID")
private Users user;

public class Users implements Serializable {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@OneToOne(mappedBy="user")
private VmUser vmUser;

@Entity
public class A implements Serializable {

@Id
private long id;

@OneToMany(mappedBy="a")
private List<MyEntity> myEntitys;

@Entity
public class B implements Serializable {

@Id
private long id;

@OneToMany(mappedBy="b")
private List<MyEntity> myEntitys;

@Entity
public class MyEntity implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private MyEntityPK id;


@ManyToOne
@JoinColumn(name="ID1")
private A a;

@ManyToOne
@JoinColumn(name="ID2")
private B b;

@Embeddable
public class MyEntityPK implements Serializable {

@Column(insertable=false, updatable=false)
private long id1;

@Column(insertable=false, updatable=false)
private long id2;

用户类

public class VmUser implements Serializable {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@OneToOne
@JoinColumn(name="ID")
private Users user;

public class Users implements Serializable {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@OneToOne(mappedBy="user")
private VmUser vmUser;

@Entity
public class A implements Serializable {

@Id
private long id;

@OneToMany(mappedBy="a")
private List<MyEntity> myEntitys;

@Entity
public class B implements Serializable {

@Id
private long id;

@OneToMany(mappedBy="b")
private List<MyEntity> myEntitys;

@Entity
public class MyEntity implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private MyEntityPK id;


@ManyToOne
@JoinColumn(name="ID1")
private A a;

@ManyToOne
@JoinColumn(name="ID2")
private B b;

@Embeddable
public class MyEntityPK implements Serializable {

@Column(insertable=false, updatable=false)
private long id1;

@Column(insertable=false, updatable=false)
private long id2;

一门课

public class VmUser implements Serializable {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@OneToOne
@JoinColumn(name="ID")
private Users user;

public class Users implements Serializable {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@OneToOne(mappedBy="user")
private VmUser vmUser;

@Entity
public class A implements Serializable {

@Id
private long id;

@OneToMany(mappedBy="a")
private List<MyEntity> myEntitys;

@Entity
public class B implements Serializable {

@Id
private long id;

@OneToMany(mappedBy="b")
private List<MyEntity> myEntitys;

@Entity
public class MyEntity implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private MyEntityPK id;


@ManyToOne
@JoinColumn(name="ID1")
private A a;

@ManyToOne
@JoinColumn(name="ID2")
private B b;

@Embeddable
public class MyEntityPK implements Serializable {

@Column(insertable=false, updatable=false)
private long id1;

@Column(insertable=false, updatable=false)
private long id2;

MyEntityPK类

public class VmUser implements Serializable {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@OneToOne
@JoinColumn(name="ID")
private Users user;

public class Users implements Serializable {

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@OneToOne(mappedBy="user")
private VmUser vmUser;

@Entity
public class A implements Serializable {

@Id
private long id;

@OneToMany(mappedBy="a")
private List<MyEntity> myEntitys;

@Entity
public class B implements Serializable {

@Id
private long id;

@OneToMany(mappedBy="b")
private List<MyEntity> myEntitys;

@Entity
public class MyEntity implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private MyEntityPK id;


@ManyToOne
@JoinColumn(name="ID1")
private A a;

@ManyToOne
@JoinColumn(name="ID2")
private B b;

@Embeddable
public class MyEntityPK implements Serializable {

@Column(insertable=false, updatable=false)
private long id1;

@Column(insertable=false, updatable=false)
private long id2;

您将id声明为主键，我认为OP希望将用户_id作为主键，我添加了ColumnMapping@SimonMartinelli请您也为实体2推荐一种方法好吗？我也为第二个实体添加了解决方案。重要的是PK类必须实现Serializable并重写equals和hashCode@SimonMartinelli是啊你的解决方案中有一个小小的疑问。您不需要添加任何映射，比如属性映射到哪个id吗？我的意思是这里我们有两个Ids注释和两个MapIds注释。那么，它将如何计算出aId对应于A或B，与投标相同？如果我错了，请纠正我。@code mode我没有任何vm\u用户列。所以我想你的答案中应该省略vm_user列。如果我错了，请纠正我。另外，关于实体2，您是否可以建议一种方法？为

vm\u用户添加id

，

vm\u用户id

。对于

MyEntity

@code模式，您可以执行相同的操作，因为vm\u用户表user\u id是主键。请更新答案。“我希望它能有所帮助。”代码模式，一个小小的疑问。在MapsId注释中，“aId”和“bId”指的是类BKey的属性，对吗？它可能不一定与基础表的实际列名相同。要做到这一点，我必须在BKey类的这些属性之上添加注释列（name=“a_id”）和列（name=“b_id”）。如果我错了，请纠正我。同时显示您的用户实体。。用户主键是int还是string？@GolamMazidSajib，id是与用户hibernate实体关联的用户表的整型主键。