programmatically asking Hibernate to recreate the database s

dportabella · **Joined:** Sun May 25, 2008 9:02 am **Posts:** 6

Hello,

I have a problem when asking Hibernate to programmatically recreate the database schema.

If I define this property in hibernate.cfg.xml

Code:

<property name="hbm2ddl.auto">create</property>

Then, this code works ok:

Code:

  Configuration config = new Configuration().configure();
  SessionFactory sessionFactory = config.buildSessionFactory();
  sessionFactory = hibernateConfiguration.buildSessionFactory();

However, if I remove that line from hibernate.cfg.xml
Then, this code does not work ok:

Code:

  Configuration config = new Configuration().configure();
  config.setProperty("hbm2ddl.auto", "create");
  SessionFactory sessionFactory = config.buildSessionFactory();
  sessionFactory = hibernateConfiguration.buildSessionFactory();

That is,
if I programmatically ask Hibernate to create the database schema,
Hibernate does not do it.

What can be the problem?

Many thanks,
DAvid

sanne.grinovero · **Posted:** Sun May 25, 2008 9:36 am

Hi, I think you should .setProperty("hbm2ddl.auto", "create") before calling configure();

dportabella · **Joined:** Sun May 25, 2008 9:02 am **Posts:** 6

s.grinovero wrote:

Hi, I think you should .setProperty("hbm2ddl.auto", "create") before calling configure();

I need to configure Hibernate from the file "hibernate.cfg.xml".
Except, that I need to override the "hbm2ddl.auto" property from that file.

So, I need to call first config.configure() to read the file "hibernate.cfg.xml".
And then to override that property.

I should be able to call config.setProperty("hbm2ddl.auto", "create") afterwards, isn't it?

DAvid

sanne.grinovero · **Posted:** Sun May 25, 2008 10:40 am

yes you are right, please forget about my previous post.
it appears configure() is just reading the file, I thought it also did some initialization, so I'm wrong.

sanne.grinovero · **Posted:** Sun May 25, 2008 10:44 am

I am using

Code:

cfg.setProperty( org.hibernate.cfg.Environment.HBM2DDL_AUTO, "create" );

in one of my projects and it is working; it turns out that the HBM2DDL_AUTO constant resolves to

Code:

"hibernate.hbm2ddl.auto"

You are having the "hibernate." missing ;-)

dportabella · **Joined:** Sun May 25, 2008 9:02 am **Posts:** 6

s.grinovero wrote:

I am using

Code:

cfg.setProperty( org.hibernate.cfg.Environment.HBM2DDL_AUTO, "create" );

in one of my projects and it is working; it turns out that the HBM2DDL_AUTO constant resolves to

Code:

"hibernate.hbm2ddl.auto"

You are having the "hibernate." missing ;-)

That's working, thanks! :)

DAvid

Cameron McKenzie · **Posted:** Sun May 25, 2008 2:43 pm

To approach this from a slightly different angle, you might even want to look at the SchemaExport class for creating the underlying database tables, as opposed to simply setting a property on the Configuration object. The SchemaExport class gives you a little bit more control over when the database will get generated, as opposed to simply regenerating when the Configuration object of Hibernate is initialized.

Hibernate.org JavaDoc for SchemaExport Object:

http://www.hibernate.org/hib_docs/v3/api/org/hibernate/tool/hbm2ddl/SchemaExport.html

Here's a simple little Hibernate3 example that uses the SchemExport class to programatically generate a database based on the various classes that make up the Configuration:

Code:

  public static void main(String args[]) {
    AnnotationConfiguration config = 
                 new AnnotationConfiguration();
    config.addAnnotatedClass(User.class);
    config.configure();
    new SchemaExport(config).create(true, true);
  }

This example can be see in more detail in this Hibernate3 and JPA tutorial:

http://www.hiberbook.com/HiberBookWeb/learn.jsp?tutorial=02validatingthehibernateenvironment

The other nice thing about the SchemaExport and SchemaUpdate objects is that they have corresponding ANT tasks, namely, SchemaExportTask and SchemaUpdateTask.