在 jpa 中使用对象作为复合主键

Question

您好，我想请您提供有关 JPA 复合主键的帮助。对于我的项目，我在 MySQL 数据库 中有不同的 table 用户、工作和参与。为此，我创建了 class 用户、工作和参与，因为在 table 参与中，我有一个复合主键，它引用用户主键和工作主键。总结以下代码涉及 class Participation 和 MyKeyParticipation.

@Entity
@ManagedBean
@IdClass(value=MyParticipationKey.class)
public class Participation {
 @Id
 @Column(name="pkIduser")
 private User user;
 @Id
 @Column(name="pkIdet")
 private Work work;
 public User getUser() {
    return user;
 }
 public void setUser(User user) {
    this.user = user;
 }
 public Work getWork() {
    return work;
 }
 public void setWork(Work work) {
    this.work = work;
 }}

并完成

public class MyParticipationKey implements Serializable {
/**
 * 
 */
 private static final long serialVersionUID = 1L;
 private User user;
 private Work work;
 public User getUser() {
    return user;
 }
 public void setUser(User user) {
    this.user = user;
 }
 public Work getWork() {
    return work;
 }
 public void setWork(Work work) {
    this.work = work;
 }   
}

以下行涉及 class 用户和工作

@Entity
@ManagedBean
public class User implements Serializable{
 @Id
 @GeneratedValue( strategy = GenerationType.IDENTITY )
 private Long pkIduser;
 @NotNull(message="Please enter your firstname")
 @Size(min=3,message="Min size 3 characters!")
 private String firstname;
 @NotNull(message="Please enter your lastname")
 @Size(min=3,message="Min size 3 characters!")
 private String lastname;
 @NotNull(message="Phone number field must not be null")
 @Size(min=5,message="Phone number must have !")
 private String phone;
 private String statut;
 @NotNull(message="Enter valid email")
 @Pattern(regexp="([^.@]+)(\.[^.@]+)*@([^.@]+\.)+    ([^.@]+)",message="please enter valid email")
 private String email;
 @NotNull(message="please enter password")
 @Size(min=3,message="Password must have 3 characters")
 private String password;
 public Long getPkIduser() {
    return pkIduser;
 }
 public void setPkIduser(Long pkIduser) {
    this.pkIduser = pkIduser;
 }
 public String getFirstname() {
    return firstname;
 }
 public void setFirstname(String firstname) {
    this.firstname = firstname;
 }
 public String getEmail() {
    return email;
 }
 public void setEmail(String email) {
    this.email = email;
 }
 public String getLastname() {
    return lastname;
 }
 public void setLastname(String lastname) {
    this.lastname = lastname;
 }
 public String getPhone() {
    return phone;
 }
 public void setPhone(String phone) {
    this.phone = phone;
 }
 public String getStatut() {
    return statut;
 }
 public void setStatut(String statut) {
    this.statut = statut;
 }
 public String getPassword() {
    return password;
 }
 public void setPassword(String password) {
    this.password = password;
 }


}

@Entity
@ManagedBean
public class Work implements Serializable{
/**
 * 
 */
 private static final long serialVersionUID = 1L;
 @Id
 @GeneratedValue( strategy = GenerationType.IDENTITY )
 private Long pkIdet;
 @NotNull(message="Enter the name")
 @Size(min=3,message="Name must have 3 characters!")
 private String name;
 private String type;
 private String description;
 private String statut;
 @ManyToOne
 @JoinColumn(name="pkIduser")
 private User user;

 public User getUser() {
    return user;
 }
 public void setUser(User user) {
    this.user = user;
 }
 public String getStatut() {
    return statut;
 }
 public void setStatut(String statut) {
    this.statut = statut;
 }
 public Long getPkIdet() {
    return pkIdet;
 }
 public void setPkIdet(Long pkIdet) {
    this.pkIdet = pkIdet;
 }
 public String getName() {
    return name;
 }
 public void setName(String name) {
    this.name = name;
 }
 public String getType() {
    return type;
 }
 public void setType(String type) {
    this.type = type;
 }
 public String getDescription() {
    return description;
 }
 public void setDescription(String description) {
    this.description = description;
 }
}

我不明白这里出了什么问题，因为我的 IDE Eclipse 告诉我来自嵌入 ID class [class gct.entities.MyParticipationKey] 的映射 [work] 是此 class 的无效映射。与嵌入式 ID 规范（来源 [class gct.entities.Participation] 中的属性 [myParticipationKey]）一起使用的可嵌入 class 只能包含基本映射。删除非基本映射或更改要嵌入的源上的嵌入 ID 规范。 请帮助我，欢迎提出任何建议。谢谢！

Answer 1

您的 @IdClass 应包含与目标实体的 @Id 字段匹配的字段。 MyParticipationKey 应该看起来像这样：

public class MyParticipationKey implements Serializable {
    private Long user;
    private Long work;
    ...
}

请注意，与正常的 @IdClass 一样，字段名称必须与实体的相应字段名称匹配（在本例中为 user 和 work）；但字段的类型必须与目标实体的主键字段的类型匹配（Long，在本例中）。

派生身份在 JPA 2.1 规范的第 2.4.1 节中进行了讨论。

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