是否可以创建具有两个主键值的实体？

Question

我遇到一个包含Entity的{​​{1}}的问题，所以也许我需要创建带有两个unique_key的{​​{1}}甚至有可能吗？

这是我的Entity

PrimaryKey

当我尝试使用另一个Entity创建此@Entity public class UserAnswerQuestion extends DateAudit { @Id @Column(name = "useranswerquestion_id") @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "useranswerquestion_seq") @SequenceGenerator(name = "useranswerquestion_seq", allocationSize = 1) private Long id; @ManyToOne private User user; @ElementCollection private List<Answer> answerList; @ManyToOne private Question question; private Boolean passed; private Boolean shown; public UserAnswerQuestion(){ } .... 时出现的问题是：

  

org.postgresql.util.PSQLException：错误：重复的键值违反了唯一约束“ uk_6v3tlg1gflua8r8d4wlqxo7v5”     详细信息：键（answer_list_answer_id）=（11）已存在。

所以我想做的就是尽可能将Entity设置为User，也许可以解决我的问题...

编辑

我所做的是，像这样创建一个类User：

@Id

然后在UserAnswerQuestionId实体中将其更改为：

public class UserAnswerQuestionId implements Serializable {

@Column(name = "useranswerquestion_id")
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "useranswerquestion_seq")
@SequenceGenerator(name = "useranswerquestion_seq", allocationSize = 1)
private Long id;

@Column(name ="user_id")
private Long user_id;

public UserAnswerQuestionId(){

}

public UserAnswerQuestionId(Long user_id) {
    this.user_id = user_id;
}

但是错误现在显示：

UserAnswerQuestion

编辑2

我正在仔细阅读错误，看起来问题出在

 @EmbeddedId
 private UserAnswerQuestionId userAnswerQuestionId;

如何解决此问题，以允许此元素在此org.hibernate.id.IdentifierGenerationException: null id generated for:class com.pew.model.useranswers.UserAnswerQuestion at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:125) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final] at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:192) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final] at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final] at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:62) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final] at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:800) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final] at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:785) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final] 上重复？

也许我可以将@ElementCollection定义为不唯一？可以在这个实体上重复吗？

这是我的@ElementCollection private List<Answer> answerList; 实体

Entity

Answer 1

也许您可能需要更好地解释用例。从上下文信息中，您似乎想 检索用户及其提供的答案 以解决各种问题。在这种情况下，您可能只需要如下所示的关联表即可。

public class User extends DateAudit { //This assumes you are intested in retrieving User and their answer(s) in the domain model.

    @Id
    private Long id; //userid.



    @ManyToMany
    @JoinTable(name = “ANSWERS_FOR_QUESTIONS”, //More appropriate name may be : ANSWERS_BY_USERS
           joinColumns = { @JoinColumn(name = “user_id”) }, //fk
           inverseJoinColumns = { @JoinColumn(name = “question_id”) }) //fk
    private Set<Answers> answers = new HashSet<Answers>();

Answer 2

主键始终只有1个且唯一。它可以是由多列元组组成的复合键。

Answer 3

使用UserAnswerQuestionId包含@IdClass应该可以：

@Entity
@IdClass(UserAnswerQuestionId.class)
public class UserAnswerQuestion extends DateAudit {

    @Id
    private Long id;

    @Id
    private Long user_id;

    @ElementCollection
    private List<Answer> answerList;
    @ManyToOne
    private Question question;

    private Boolean passed;

    private Boolean shown;

    public UserAnswerQuestion(){
    }