Hi,
I'm new to hibernate. I use struts, tomcat postgresql db in my project. I add some entities into table. But when i re-run my project, the new entities aren't appended to table.
For example, for the first time I add sth to table, it is like

ZZZ TABLE
1 aaa bbb ccc
2 ddd eee fff
3 ggg hhh iii
4 jjj kkk lll
5

But after re-running, it doesn't append the new objects although it adds into the table

ZZZ TABLE:
1 mmm nnn ooo
2

( "5 mmm nnn ooo" is expected)



My code:

...
News nw = new News();
nw.setHeader("aaa");
nw.setContent("bbb");
nw.setSource("ccc");
NewsOperations.createNews(nw);

...

public static void createNews(News nw) {
Transaction tx = null;
Session session = HibernatePlugIn.getInstance.getCurrentSession();
try {
tx = session.beginTransaction();
session.save(nw);
tx.commit();
}catch (HibernateException e) {
e.printStackTrace();
if (tx != null && tx.isActive())
tx.rollback();
}
}

...



import javax.naming.InitialContext;
import org.apache.log4j.Logger;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.cfg.Environment;

public class HibernatePlugIn {

private HibernatePlugIn() {
}

private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
private static final Configuration cfg = new Configuration();
private static org.hibernate.SessionFactory sessionFactory;

public static SessionFactory getInstance() {
if (sessionFactory == null)
initSessionFactory();
return sessionFactory;
}

public Session openSession() {
return sessionFactory.getCurrentSession();
}

public Session getCurrentSession() {
return sessionFactory.getCurrentSession();
}

private static synchronized void initSessionFactory() {
Logger log = Logger.getLogger(HibernatePlugIn.class);
if (sessionFactory == null) {
try {
cfg.configure(CONFIG_FILE_LOCATION);
String sessionFactoryJndiName = cfg
.getProperty(Environment.SESSION_FACTORY_NAME);
if (sessionFactoryJndiName != null) {
cfg.buildSessionFactory();
log.debug("get a jndi session factory");
sessionFactory = (SessionFactory) (new InitialContext())
.lookup(sessionFactoryJndiName);
} else{
log.debug("classic factory");
sessionFactory = cfg.buildSessionFactory();
}
} catch (Exception e) {
System.err
.println("%%%% Error Creating HibernateSessionFactory %%%%");
e.printStackTrace();
throw new HibernateException(
"Could not initialize the Hibernate configuration");
}
}
}

public static void close(){
if (sessionFactory != null)
sessionFactory.close();
sessionFactory = null;

}
}


...

Hibernate.cfg.xml

<session-factory>
<!-- PostgreSQL connection -->
<property name="connection.url">jdbc:postgresql://localhost/db</property>
<property name="connection.username">postgres</property>
<property name="connection.password">1234</property>
<property name="connection.driver_class">org.postgresql.Driver</property>
<property name="dialect">org.hibernate.dialect.PostgreSQLDialect</property>


<property name="transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>
<property name="current_session_context_class">thread</property>
<property name="hibernate.show_sql">true</property>
<property name="hibernate.hbm2ddl.auto">create</property>
<mapping resource="package/News.hbm.xml" />

</session-factory>


...

News.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping package="package">
<class name="News" table="news" >
<id name="id" >
<generator class="sequence">
<param name="sequence" >news_id_seq</param>
</generator>
</id>
<property name="header" type="string"></property>
<property name="content" type="string"></property>
<property name="source" type="string"></property>
</class>

</hibernate-mapping>

I think your problem has to do with your
<property name="hibernate.hbm2ddl.auto">create</property>
In your config file. This property tells hibernate to drop the table and rebuild every time. If you want hibernate to generate your schema the first time use this property set as you have it. Once you have your tables created in your DB comment out this property and then use your update command. I think that will fix your problem.

Yes, it solved. Thanks.