Internal Exception: java.sql.SQLException: Invalid state, the Connection object is closed - jpa

Question

I have a JSF application that uses Eclipse Persistence Services - 2.1.1.v20100817-r8050, and I sometimes get the following error:
Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.1.1.v20100817-r8050): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: java.sql.SQLException: Invalid state, the Connection object is closed.
Error Code: 0
Call: SELECT XXXXX FROM XXXXX
bind => [/Home/Footer/]
Query: ReadAllQuery(name="WWW.find" referenceClass=WWW sql="SELECT XXXXX FROM XXXXX")
I have no idea what is causing it. The exception is thrown in the following function on the "return q.getResultList();" line.
public List<WWW> find(String url) {
}
EntityManager em = getEntityManager();
try {
Query q = em.createNamedQuery("WWW.find");
q.setParameter("url", url);
return q.getResultList();
} finally {
em.close();
}
}
We have SQL Server 2005 and the database isn't down. This is more of a recent thing to consistently happen. Below is the properties that we set in the persistence.xml file. Any comments on what should change in this?
<properties>
<property name="javax.persistence.jdbc.password" value="password"/>
<property name="javax.persistence.jdbc.user" value="user"/>
<property name="javax.persistence.jdbc.driver" value="net.sourceforge.jtds.jdbc.Driver"/>
<property name="javax.persistence.jdbc.url" value="jdbc:jtds:sqlserver://SERVER:1433/DB"/>
<property name="eclipselink.ddl-generation" value="none"/>
<property name="eclipselink.jdbc.timeout" value="20"/>
<property name="eclipselink.jdbc.connections.wait-timeout" value="20"/>
<property name="javax.persistence.query.timeout" value="20"/>
<property name="eclipselink.allow-zero-id" value="true"/>
</properties>
Here is my edited class
public class WWWJpaController {
public WWWWJpaController() {
emf = Persistence.createEntityManagerFactory("properties");
}
public WWWWJpaController(String unitName) {
emf = Persistence.createEntityManagerFactory(unitName);
}
private EntityManagerFactory emf = null;
public EntityManager getEntityManager() {
return emf.createEntityManager();
}
public List<WWW> find(String url) {
EntityManager em = getEntityManager();
try {
Query q = em.createNamedQuery("WWW.find");
q.setParameter("url", url);
return q.getResultList();
}finally{
em.close();
}
}
}

Answer 1

My guess is your database connection has timed out, or your database is down.
You may need to retry the query, or re-connect your session.
How have you configured your connection pooling and what database are you using?

Answer 2

Maybe your aplication server is not able to reconnect to the database, as BalusC pointed out in his comment, this happens every time the backup's done.
You can make your server reconnect as pointed in this link for Jboss