HSQLDB and Hibernate/JPA - not persisting to disk?

Question

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.

Answer 1

Did you set hibernate.hbm2ddl.auto to create-drop in your persistence.xml? This drops your tables and re-creates them on every startup.

You can set it to update instead, or if you want to manage the schema yourself, then set it to validate.

Answer 2

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

Answer 3

The solution is :

<property name="dialect">org.hibernate.dialect.HSQLDialect</property>

in hibernate.cfg.xml

---

This is rest of my configuration:

Libs:

• HsqlDb 2.0.0
• Hibernate 3.5.6

Url:

<property name="connection.url">jdbc:hsqldb:file:data/mydb;shutdown=true;hsqldb.write_delay=false;</property>