Using EntityManager the right way in a Tomcat Servlet

schade · **Joined:** Wed Aug 18, 2004 10:44 am **Posts:** 14

Hibernate version:
3.2

As far as I know, when using the entitymanager in Tomcat you must look up how to do it in an J2SE environment.

Im trying to use the persistence API, entity manager and annotations. My servlet code looks like this:

Code:

public class Admin extends HttpServlet {

 private static final long serialVersionUID = 1L;
 
 
 @SuppressWarnings("unchecked")
 protected void doGet( HttpServletRequest request, 
      HttpServletResponse response )
                                throws ServletException, IOException {
  // The output is a html-page.
  response.setContentType( "text/html" );
  PrintWriter out = response.getWriter();  
  out.print("...");
  EntityManagerFactory emf =  Persistence.createEntityManagerFactory("manager1");
  EntityManager em = emf.createEntityManager(); 
  try {
         EntityTransaction tx = em.getTransaction();
         tx.begin();
         // create new entity
         Institution inst = new Institution();
         inst.setNavn(nyInstNavn);
         em.persist(inst);
         tx.commit();
         out.print("<p>Added new:"+nyInstNavn+"</p>");
   } catch (Exception e) {
      out.print("<p><b>WOW</b> exception</p>");
   } finally {
     em.close();
   }
}

The servlet runs fine - until the servlet is ran a 100 times, then an exception is thrown:

Code:

javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Cannot open connection
   at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:647)
   at org.hibernate.ejb.TransactionImpl.begin(TransactionImpl.java:40)
   at com.hypergenic.weboverblik.servlets.Admin.doGet(Admin.java:76)
...
Caused by: org.hibernate.exception.JDBCConnectionException: Cannot open connection
   at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:74)
   at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
   at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:29)
   at org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:420)
   at org.hibernate.jdbc.ConnectionManager.getConnection(ConnectionManager.java:144)

It seems like all the connections to the database are in use. But the entitymanager and the entitytransaction are both created in the doGet() method. This should ensure cleanup of the connections, right?

Regards,
René

schade · **Joined:** Wed Aug 18, 2004 10:44 am **Posts:** 14

Moved EntityManagerFactory into a static @PersistenceUnit

Code:

@PersistenceUnit EntityManagerFactory emf = Persistence.createEntityManagerFactory("manager1");
   

According to:

https://blueprints.dev.java.net/bpcatal ... lyapp.html

I'm running a "Application-Managed Entity Managers"

Regards,
Rene

MikePloed · **Posted:** Mon Nov 13, 2006 8:04 am

Please check the configuration of your datasource / database in the persistence.xml. Somehow you can't get to the database

schade · **Joined:** Wed Aug 18, 2004 10:44 am **Posts:** 14

Sorry, I forgot to mention in my previous post, that moving Moved EntityManagerFactory into a static @PersistenceUnit fixed the problem for me.

Just curius: It seems like not many people are using the Java Persistence API in a Servlet-environment. Or am I wrong here?

Regards,
René

MikePloed · **Posted:** Mon Nov 13, 2006 9:25 am

It is absolutely fine for you to use JPA in a servlet environment.