NoClassFoundDefError

su · **Joined:** Mon Aug 02, 2004 5:33 am **Posts:** 4

Hi
I'm new to Hibernate. I'm using Hibernate 2.1.3, Mysql 4.0.12 and Tomcat 5.

I'm using the example HibernateUtilities class and my DAO class uses it to get the current session.

Here's the HibernateUtilities class:

Code:

package com.cms.server.util;


import net.sf.hibernate.HibernateException;
import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.cfg.Configuration;

/**
 * 
 * @author 
 *
 */
public class HibernateUtil 
{
   private static final SessionFactory sessionFactory;
   public static final ThreadLocal session = new ThreadLocal();

   static 
   {
      try 
      {
         // Create the SessionFactory
         sessionFactory = new Configuration().configure().buildSessionFactory();
      } 
      catch (HibernateException ex) 
      {
         throw new RuntimeException("Configuration problem: " + ex.getMessage(), ex);
      }
   }

   
   public static Session currentSession() throws HibernateException 
   {
      Session s = (Session) session.get();
      // Open a new Session, if this Thread has none yet
      if (s == null) 
      {
         s = sessionFactory.openSession();
         session.set(s);
         System.out.println("creating sessionFactory");
      }
      System.out.println("Returning session.");
      return s;
   }

   public static void closeSession() throws HibernateException
   {
      System.out.println("HibernateUtil.closeSession: inside the method.");
      try
      {
         Session s = (Session) session.get();
         session.set(null);
         if (s != null)
            s.close();
      }
      catch(Throwable t){
         t.printStackTrace();
      }
   }

}

I'm getting NoClassDefFoundError when I run my test servlet that uses the DAO.

Here's the stack trace:

2004-08-02 10:41:52 StandardWrapperValve[TestHibernateServlet]: Servlet.service() for servlet TestHibernateServlet threw exception
java.lang.NoClassDefFoundError
at com.cms.server.database.hibernate.HibernateUserDAO.getUserByUsernamePassword(Unknown Source)
at com.cms.server.servlet.TestHibernateServlet.doGet(Unknown Source)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:697)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:793)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:702)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:571)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:644)
at java.lang.Thread.run(Thread.java:536)

I have set up my Classpath as in the qucikstart guide.

Thanks for any help

[/code]

christian · **Posted:** Mon Aug 02, 2004 6:47 am

There was an error in the Quickstart not so long ago, please use the following static initializer in HibernateUtil:

Code:

   // Create the initial SessionFactory from the default configuration files
   static {
      try {
         configuration = new Configuration();
         sessionFactory = configuration.configure().buildSessionFactory();
         // We could also let Hibernate bind it to JNDI:
         // configuration.configure().buildSessionFactory()
      } catch (Throwable ex) {
         // We have to catch Throwable, otherwise we will miss
         // NoClassDefFoundError and other subclasses of Error
         log.error("Building SessionFactory failed.", ex);
         throw new ExceptionInInitializerError(ex);
      }
   }

jsp1611 · **Joined:** Mon Dec 08, 2003 8:09 am **Posts:** 25

Hi Chritian,
I'm not sure what the difference is between the static iniitializer you posted and the one that Su posted?

As far as I can see the only difference is that the one that you posted catches Errors as well as Exceptions..

Is the idea to get the stack trace from inside the static initializer and try and find out whats going from from there.

Jon

christian · **Posted:** Mon Aug 02, 2004 7:58 am

The idea is to catch Errors instead of Exceptions. Read the comment...

jsp1611 · **Joined:** Mon Dec 08, 2003 8:09 am **Posts:** 25

I did. I have a similar error. My point was that the code doesnt solve the problem, it just allows you to catch the NoClassDefFoundError and do *something* with it.

Let me rephrase: have you any ideas as to what might be causing the Error in the first place?

Jon

christian · **Posted:** Mon Aug 02, 2004 11:46 am

Guys, its so trivial: The catch allows you to _SHOW_ the error that was the cause of the problem. It will get swallowed otherwise.