Thanks for your precisions. I read the documentation to configure JBoss, it seems it never ends, I always discover new things to do. So now, I have the famous mysql-ds.xml that I added to JBOSSHOME/server/myapp/deploy as follow: <datasources> | <local-tx-datasource> | <jndi-name>cuoreds</jndi-name> | <connection-url>jdbc:mysql://localhost:3306/cuore</connection-url> | <driver-class>com.mysql.jdbc.Driver</driver-class> | <user-name>root</user-name> | <password>123456</password> <exception-sorter-class-name>org.jboss.resource.adapter.jdbc.vendor.MySQLExceptionSorter</exception-sorter-class-name> | <new-connection-sql>cuore</new-connection-sql> | <!-- corresponding type-mapping in the standardjbosscmp-jdbc.xml --> | <metadata> | <type-mapping>mySQL</type-mapping> | </metadata> | </local-tx-datasource> | </datasources> Then I had an error of jbdc driver, so I dowloaded it , put the sqljdbc.jar in JBOSSHOME/server/myapp/lib, added it in the BUILDPATH in Eclipse and added it in the deploy folder, even if I'm not sure it's really useful. Then I did the same with the mysql-connector-java-5.0.8-bin.jar. But it still doesn't work...:´( Here is the log 2008-06-04 13:28:03,583 DEBUG [org.jboss.util.NestedThrowable] org.jboss.util.NestedThrowable.detectDuplicateNesting=true 2008-06-04 13:28:03,583 WARN [org.jboss.resource.connectionmanager.JBossManagedConnectionPool] Throwable while attempting to get a new connection: null org.jboss.resource.JBossResourceException: Could not create connection; - nested throwable: (com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'cuore' at line 1) at org.jboss.resource.adapter.jdbc.local.LocalManagedConnectionFactory.createManagedConnection(LocalManagedConnectionFactory.java:179) at org.jboss.resource.connectionmanager.InternalManagedConnectionPool.createConnectionEventListener(InternalManagedConnectionPool.java:577) at org.jboss.resource.connectionmanager.InternalManagedConnectionPool.getConnection(InternalManagedConnectionPool.java:262) at org.jboss.resource.connectionmanager.JBossManagedConnectionPool$BasePool.getConnection(JBossManagedConnectionPool.java:500) at org.jboss.resource.connectionmanager.BaseConnectionManager2.getManagedConnection(BaseConnectionManager2.java:341) at org.jboss.resource.connectionmanager.TxConnectionManager.getManagedConnection(TxConnectionManager.java:315) at org.jboss.resource.connectionmanager.BaseConnectionManager2.allocateConnection(BaseConnectionManager2.java:396) at org.jboss.resource.connectionmanager.BaseConnectionManager2$ConnectionManagerProxy.allocateConnection(BaseConnectionManager2.java:842) at org.jboss.resource.adapter.jdbc.WrapperDataSource.getConnection(WrapperDataSource.java:88) at org.hibernate.ejb.connection.InjectedDataSourceConnectionProvider.getConnection(InjectedDataSourceConnectionProvider.java:47) at org.hibernate.cfg.SettingsFactory.buildSettings(SettingsFactory.java:84) at org.hibernate.cfg.Configuration.buildSettings(Configuration.java:2009) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1292) at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:713) at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFactory(HibernatePersistence.java:127) at org.jboss.ejb3.entity.PersistenceUnitDeployment.start(PersistenceUnitDeployment.java:246) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ... and tons of lines. It also says me this at the end: Caused by: org.hibernate.HibernateException: Hibernate Dialect must be explicitly set I'm lost and desperate... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4155641#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...