通过坚持在Hibernate中实体的不同标识符

Question

当我创建一个没有ID的新实体并将其存储在数据库中时，实体将接收除数据库中标识符以外的标识符。 ID是通过oracle中的序列生成的。任何建议如何解决它？感谢您的回复。

示例：我创建了DiReview review = new DiReview（）。我设置正确的所有领域，除了ID我希望通过getSessionFactory（）。getCurrentSession（）。持久化（）审查数据库，我希望休眠设置正确的ID。假设oracle序列生成的最后一个ID是25，所以我假设表DI_REVIEW中的新行将是26.在表中存储并提交之后，确实存储了具有id 26的新行，但是在审阅中设置了字段id另一个数字。在我的情况下，例如2000！这个是正常的？

这个问题在我的案例中不仅涉及到DiReview，而且涉及我所有的实体。当我从数据库加载实体时，加载了corect id。

编辑 - 我尝试使用Oracle和序列来实现这个example和至少现在我知道这是不正常的行为;-)

@Entity 
@Table(name = "DI_REVIEW", uniqueConstraints = @UniqueConstraint(columnNames = { 
     "OBJECT_ID", "USER_ID" })) 
public class DiReview{ 

    private Long id; 
    private DiUser user; 
    private DiObject object; 
    private String text; 
    private Date createDate; 

    private Set<DiRating> ratings = new HashSet<DiRating>(0); 
    private Set<DiReviewContext> reviewContexts = new HashSet<DiReviewContext>(
      0); 

    private Collection<DiReviewContext> reviewContextsList = new ArrayList<DiReviewContext>(); 
    private Set<DiComment> comments = new HashSet<DiComment>(0); 

    public DiReview() { 
    } 

    public DiReview(Long id, DiUser user, DiObject object, String text, 
      Date createDate) { 
     this.id = id; 
     this.user = user; 
     this.object = object; 
     this.text = text; 
     this.createDate = createDate; 
    } 

    @Id 
    @Column(name = "ID", unique = true, nullable = false, precision = 18, scale = 0) 
    @SequenceGenerator(name = "di_review_seq", sequenceName = "DI_REVIEW_SEQ") 
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "di_review_seq") 
    public Long getId() { 
     return this.id; 
    } 

    getters and setters .. 

    @Override 
    public int hashCode() { 
     final int prime = 31; 
     int result = 1; 
     result = prime * result 
       + ((createDate == null) ? 0 : createDate.hashCode()); 
     result = prime * result + ((id == null) ? 0 : id.hashCode()); 
     result = prime * result + ((object == null) ? 0 : object.hashCode()); 
     result = prime * result + ((text == null) ? 0 : text.hashCode()); 
     result = prime * result + ((user == null) ? 0 : user.hashCode()); 
     return result; 
    } 

    @Override 
    public boolean equals(Object obj) { 
     if (this == obj) 
      return true; 
     if (obj == null) 
      return false; 
     if (getClass() != obj.getClass()) 
      return false; 
     DiReview other = (DiReview) obj; 
     if (createDate == null) { 
      if (other.createDate != null) 
       return false; 
     } else if (!createDate.equals(other.createDate)) 
      return false; 
     if (id == null) { 
      if (other.id != null) 
       return false; 
     } else if (!id.equals(other.id)) 
      return false; 
     if (object == null) { 
      if (other.object != null) 
       return false; 
     } else if (!object.equals(other.object)) 
      return false; 
     if (text == null) { 
      if (other.text != null) 
       return false; 
     } else if (!text.equals(other.text)) 
      return false; 
     if (user == null) { 
      if (other.user != null) 
       return false; 
     } else if (!user.equals(other.user)) 
      return false; 
     return true; 
    } 

    @Override 
    public String toString() { 
     return "DiReview [id=" + id + ", user=" + user + ", object=" + object 
       + ", text=" + text + ", createDate=" + createDate + "]"; 
    } 

} 

    public T makePersistent(T entity) { 
    try { 

     getSessionFactory().getCurrentSession().persist(entity); 

    } catch (Exception e) { 
     e.printStackTrace(); 
    } 
    return entity; 
} 

Answer 1

我不知道这是否解决您的问题，而是何时使用序列生成器，默认情况下，Hibernate一次分配一个包含50个ID值的块，这可能意味着它无法获取您期望的序列值。您可以通过更改注释为@SequenceGenerator如下改变这一点：

@SequenceGenerator(name = "di_review_seq", sequenceName = "DI_REVIEW_SEQ", 
     allocationSize = 1)