我的ID是如何使用Hibernate与Oracle 10g方言一起使用JPA生成的？ [英] How is my id being generated with JPA using Hibernate with the Oracle 10g dialect?

问题描述

我有一些代码：

  @Id 
 @SequenceGenerator（name =SOMETHING_SEQ）
 @GeneratedValue（strategy = GenerationType.SEQUENCE，generator =SOMETHING_SEQ）
 @Column（name =SOMETHING，nullable = false）
私有长ID; 
  

hibernate如何提供我的id？

我在我的数据库中看到一个名为'hibernate_sequence'的序列，并且没有其他hibernate'特殊表'。

SOMETHING_SEQ 是你在你的休眠配置中某处配置的序列的名字。而 hibernate_sequence 是数据库中的序列名称。
$ b

 < sequence-generator name =SOMETHING_SEQ
 sequence- name =hibernate_sequence
 allocation-size =< any_number_value>/> 
  

您可以使用注释完全跳过此配置。然后你的 @SequenceGenerator 注释需要提供更多的参数。下面是这个例子。

  @SequenceGenerator（name =SOMETHING_SEQ，sequenceName =hibernate_sequence，allocationSize = 10）
  

例如，多个实体类可以做类似下面的事情，

  @Entity 
 public class Entity1 {
 @Id 
 @SequenceGenerator（name =entity1Seq，sequenceName =ENTITY1_SEQ，allocationSize = 1 ）
 @GeneratedValue（strategy = GenerationType.SEQUENCE，generator =entity1Seq）
 @Column（name =ID，nullable = false）
 private long ID; 
 
 ... 
 ... 
 
} 
 
 @实体
公共类实体2 {
 @ Id 
 @SequenceGenerator（name =entity2Seq，sequenceName =ENTITY2_SEQ，allocationSize = 10）
 @GeneratedValue（strategy = GenerationType.SEQUENCE，generator =entity2Seq）
 @Column name =ID，nullable = false）
私有长ID; 
 
 ... 
 ... 
 
} 
  

I have some code:

@Id
@SequenceGenerator(name = "SOMETHING_SEQ")
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SOMETHING_SEQ")
@Column(name = "SOMETHING", nullable = false)
private Long id;

How is hibernate providing my id?

I see in my database there a single sequence named 'hibernate_sequence' and no other hibernate 'special tables'.

解决方案

Actually, here your SOMETHING_SEQ is the name of sequence you configured somewhere in your hibernate config. And hibernate_sequence is the sequence name in the database. In configuration it would be looking something like below,

<sequence-generator name="SOMETHING_SEQ" 
    sequence-name="hibernate_sequence"
    allocation-size="<any_number_value>"/>

You can completely skip this configuration by using annotation instead. Then your @SequenceGenerator annotation would need to provide few more paramters. Below is the example.

@SequenceGenerator(name="SOMETHING_SEQ", sequenceName="hibernate_sequence", allocationSize=10)

For example multiple entity classes would do something like below,

@Entity
public class Entity1 {
  @Id
  @SequenceGenerator(name = "entity1Seq", sequenceName="ENTITY1_SEQ", allocationSize=1)
  @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "entity1Seq")
  @Column(name = "ID", nullable = false)
  private Long id;

  ...
  ...

}

@Entity
public class Entity2 {
  @Id
  @SequenceGenerator(name = "entity2Seq", sequenceName="ENTITY2_SEQ", allocationSize=10)
  @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "entity2Seq")
  @Column(name = "ID", nullable = false)
  private Long id;

  ...
  ...

}

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