Oracle Trigger用于从序列中生成id的HIbernate问题

问题描述

我们有一个before插入触发器，它从序列中获取下一个值。当对象用save（）方法持久化时，hibernate从序列中获取值并将其添加到对象中。当事务从Spring的服务层提交时，数据库上的ID值再次增加。如何避免获得nextval（）如果对象已经有一个ID ..

这是我可以做的事情..

UserDao

  public User saveUser（User user）{
 session.getCurrentSession.save用户）; // line2 
 return user; // line3 
} 
  

UserService

  public void saveUserAndWriteToAudit（User user，UserAudit userAudit）{
 userDao.saveUser（user）; // line1 
 userAudit.setUserId（user.getId）; // line4 
 userAudit.saveUserAudit（userAudit）; // line5 
} 
  

和User Class

  @Entity 
 public class用户{
 
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO，generator =a1）
 @SequenceGenerator（name =a1，sequenceName =usersequence） 
私人长ID; 
 ///////////////// 
} 
  

当光标到达line1且line2用户对象在id属性中为null时。在line2之后，它具有sequence的nextval - 让我说1在line4上，我已经添加了用户的id = 1来使用审查对象..当事务在第5行后被提交时，2被插入到用户的id列中并且1被插入到UserAudit的userId列中。这对我来说没有任何用处:(我怎样才能避免这个问题？谢谢！

 创建或替换
触发sa.my_trigger 
插入sa.my_table之前每行
 
（new.id为空）
 begin 
选择sa.my_sequence.nextval 
 into：new.id 
 from dual; 
 end; 
  

We have a before insert trigger that gets the next value from sequence. When the object is persisted with save() method, hibernate gets the value from the sequence and adds it to the object. and when the transaction is committed from Spring's service layer, the ID value is again increased on the database. how do I avoid getting nextval() if the object already has an id..

Here is what I ma trying to do..

UserDao

public User saveUser(User user){
      session.getCurrentSession.save(user);//line2
      return user;//line3
 }

UserService

public void saveUserAndWriteToAudit(User user, UserAudit userAudit){
  userDao.saveUser(user);//line1
  userAudit.setUserId(user.getId);//line4
  userAudit.saveUserAudit(userAudit);//line5
}

And the User Class

 @Entity
  public class User{

     @Id
     @GeneratedValue(strategy=GenerationType.AUTO, generator="a1")
     @SequenceGenerator(name="a1", sequenceName="usersequence")
     private Long id;
     /////////////////
 }

When the cursor reaches line1 and line2 user object has null in id attribute. after line2, it has nextval from sequence - lets say 1. on line4, i have added user's id=1 to useraudit object.. when transaction is committed after line 5, 2 is inserted into User's id column and 1 into UserAudit's userId column. This serves no purpose to me :( How do I avoid this issue? Thanks!

解决方案

Just update your trigger to only fire when not given an id.

create or replace
trigger sa.my_trigger
before insert on sa.my_table
for each row
when (new.id is null)
begin
   select sa.my_sequence.nextval
    into :new.id
    from dual;
end;

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