HSQLDB和Hibernate / JPA - 不会持久化到磁盘？ [英] HSQLDB and Hibernate/JPA - not persisting to disk?

问题描述

  em.getTransaction（）。begin（）;这是一个使用HSQL和Hibernate的新手。 
 for（Activity theActivity：activities）{
 em.persist（theActivity）; 
} 
 em.getTransaction（）。commit（）; 
 em.close（）; 
  

后面是...

  EntityManager em = emf.createEntityManager（）; 
 em.getTransaction（）。begin（）; 
 System.out.println（QUERY ::
 + em.createQuery（SELECT COUNT（*）FROM+ Activity.class.getName（））。getSingleResult（）
。的toString（））; 
 em.getTransaction（）。commit（）; 
  

打印25000（活动中的活动对象数）。但是当我再次运行此测试时，计数（*）中的对象数量不会增加（并且在程序开始时为0）。因此，这些对象不会变得持久。

这是我的hsqldb连接字符串：

  name =hibernate.connection.urlvalue =jdbc：hsqldb：file：data / cmon
  

所以它不是一个内存中的数据库，据我所知...

有没有人有任何想法，为什么对象没有得到坚持超越单个JVM会话？很高兴能提供更多的信息，但是与Hibernate / JPA / HSQL有很多相关的状态，所以我们不清楚究竟是什么相关的。

有没有人有任何想法，为什么这些对象不会在单个JVM会话之外持久保存？

在提交后，HSQLDB不会立即将更改写入磁盘（请参阅 WRITE DELAY ），HSQLDB在默认情况下是不可持久的（这来自performance来自哪里）。

尝试在连接字符串中设置连接属性 shutdown = true ，以获取上次连接结束时写入的更改。

  jdbc：hsqldb：file：data / cmon; shutdown = true 
  

如果没有帮助，请尝试设置 WRITE DELAY 为0（或false）。如果您使用HSQLDB 1.8.x，请使用SQL命令：

  SET WRITE_DELAY 0 
    
 
 $ b 
 .net / doc / 2.0 / guide / dbproperties-chapt.htmlrel =noreferrer>属性  hsqldb.write_delay ：
  jdbc：hsqldb：file：data / cmon; hsqldb.write_delay = false 
  
 
Something of an novice with HSQL and Hibernate...
em.getTransaction().begin();
for (Activity theActivity : activities) {
  em.persist(theActivity);
}
em.getTransaction().commit();
em.close();
followed by...
EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
System.out.println("QUERY:: "
    + em.createQuery("SELECT COUNT(*) FROM " + Activity.class.getName()).getSingleResult()
        .toString());
em.getTransaction().commit();
Prints 25000 (the number of Activity objects in activities). But when I run this test again, the number of objects in the count(*) doesn't increase (and is 0 at the beginning of the program). So the objects aren't getting durably written.

This is my hsqldb connection string:
name="hibernate.connection.url" value="jdbc:hsqldb:file:data/cmon"
so it's not an in-memory database as far as I know...

Does anyone have any ideas why the objects aren't getting persisted beyond a single JVM session? Happy to supply more information but there's so much state associated with Hibernate / JPA / HSQL that it's not clear exactly what is pertinent.
解决方案

  
Does anyone have any ideas why the objects aren't getting persisted beyond a single JVM session? 
HSQLDB doesn't write changes immediately to disk after a commit (see "WRITE DELAY"), HSQLDB is not Durable by default (that's from where "performances" are coming from).

Either try to set the connection property shutdown=true in the connection string to get the changes written when the last connection will end.
jdbc:hsqldb:file:data/cmon;shutdown=true
If it doesn't help, try to set the WRITE DELAY to 0 (or false). If you're using HSQLDB 1.8.x, use the SQL command:
SET WRITE_DELAY 0
If you're using HSQLDB 2.0.x, you can now also use a connection property hsqldb.write_delay: 
jdbc:hsqldb:file:data/cmon;hsqldb.write_delay=false


                        
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