Session creation falied - error

[Shashank Rudra]

Hi

I am trying to create a session in Hibernate. I am using

Session session = HibernateUtil.getSessionFactory().getCurrentSession();		
session.beginTransaction();

with all the jar in place and no other error coming. I have put this code in a servlet. The whole code goes like this.

package com.hibernate.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.hibernate.*;

import com.hibernate.utils.*;
import com.hibernate.beans.*;

/**
 * Servlet implementation class for Servlet: TestHibernate
 *
 */
 public class TestHibernate extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet {
   static final long serialVersionUID = 1L;
   
    /* (non-Java-doc)
	 * @see javax.servlet.http.HttpServlet#HttpServlet()
	 */
	public TestHibernate() {
		super();
	}   	
	
	/* (non-Java-doc)
	 * @see javax.servlet.http.HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
	
		System.out.println("in TestHibernate Servlet.");
		Session session = HibernateUtil.getSessionFactory().getCurrentSession();		
		session.beginTransaction();
		
		//select the rows from Color Table
  	    List result = session.createQuery("from Color").list();
		
		PrintWriter out = response.getWriter();
		out.println("In this page hibernate code will be called.");
		
		for(int i=0;i<result.size();i++){
			Color tClr = (Color)result.get(i);
			out.println("Id: " + tClr.getId() + "  Color: " + tClr.getColor());
		}
		
		session.getTransaction().commit();
		HibernateUtil.getSessionFactory().close();
		
		return;		
	}  	
	
	/* (non-Java-doc)
	 * @see javax.servlet.http.HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
	}   	  	    
}

I am getting error

Initial SessionFactory creation failed.java.lang.IncompatibleClassChangeError

HibernateUtil class is

package com.hibernate.utils;

import org.hibernate.*;
import org.hibernate.cfg.*;

public class HibernateUtil {

	private static final SessionFactory sessionFactory;
	
	static{
		try{
			sessionFactory = new Configuration().configure().buildSessionFactory();		
		}
		catch(Throwable ex) {
            // Make sure you log the exception, as it might be swallowed
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
		}		
	}
	
	public static SessionFactory getSessionFactory(){
		return sessionFactory;
	}
	
}

The configuration xml file is hibernate.cfg.xml

><?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC  "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="connection.driver_class">com.microsoft.jdbc.sqlserver.SQLServerDriver</property>
        <property name="connection.url">jdbc:microsoft:sqlserver://20.15.4.84:1433;EZRhythm</property>
        <property name="connection.username">sa</property>
        <property name="connection.password">******</property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.SQLServerDialect</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">create</property>

        <mapping resource="com/hibernate/beans/Color.hbm.xml"/>

    </session-factory>

</hibernate-configuration>

What I am doing wrongly, please someone help me here.

[Paul Sturrock]

What does the error message say? Do you have a stack trace you can post?

[Shashank Rudra]

no stack trace this is what I am getting in the console -

the test string(Sys.out code that I am putting on the top of the TestHibernate servlet) followed by the error message -

Initial SessionFactory creation failed.java.lang.IncompatibleClassChangeError

Hope this helps. Please ask me for more details.

[Paul Sturrock]

Sounds like a deployment issue. Clear down your container's temporary directories and redeploy you application.

[Rahul Babbar]

Giffy Geraldo wrote:

System.err.println("Initial SessionFactory creation failed." + ex);

change the above to

System.err.println("Initial SessionFactory creation failed." + ex.printStackTrace());

for a full stack trace.

[Shashank Rudra]

ok you meant

System.err.println("Initial SessionFactory creation failed.");
ex.printStackTrace();

Thanks. I am trying these options.

[Shashank Rudra]

Here is the stack trace.

Initial SessionFactory creation failed.
java.lang.IncompatibleClassChangeError
	at org.hibernate.cfg.Environment.<clinit>(Environment.java:543)
	at org.hibernate.cfg.Configuration.reset(Configuration.java:201)
	at org.hibernate.cfg.Configuration.<init>(Configuration.java:220)
	at org.hibernate.cfg.Configuration.<init>(Configuration.java:224)
	at com.hibernate.utils.HibernateUtil.<clinit>(HibernateUtil.java:12)
	at com.hibernate.servlet.TestHibernate.doGet(TestHibernate.java:36)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

[Shashank Rudra]

Here is a link to similar problem
http://www.coderanch.com/t/218728/Object-Relational-Mapping/java/IncompatibleClassChangeError

So I tried with different options - earlier I was putting the hibernate.cfg.xml in the app folder only. Now I have moved it to classes folder. I dun know why is that? I was following a youtube video to create a hibernate project, earlier by not putting it in the classes folder.

now it seems the classChnageError is gone.

Would some one please help me understand how to deplpy these config xmls, log4j.prop files etc for hibernate application. TIA.

[Paul Sturrock]

So I tried with different options - earlier I was putting the hibernate.cfg.xml in the app folder only. Now I have moved it to classes folder. I dun know why is that? I was following a youtube video to create a hibernate project, earlier by not putting it in the classes folder.

"app folder", what do you mean by that? If you are deploying a web application you need to include the Hibernate configuration file on the classpath. If you are using the default configuration this need to be at the root of your classpath. Web applications have specified folders* that are included in the classpath. If you don't use these it will be up to how you configure your servlet container's classloader to pick dependent files up.

However, an IncompatibleClassChangeError is not what I would expect if you had put hibernate.cfg.xml in the wrong place. An erro like that usually only happens as the result of hot deployment.

*(If this is something you were not aware of I would go through the servlet parts of this before trying anything more with Hibernate)

[Shashank Rudra]

Thanks guys for quick response.

Thanks Paul for pointing that out. However I have one more query related to the directory structure and places where you need to put the various descriptors, context files etc. If we are using Eclipse as IDE - will the package hierarchy be same for Netbeans IDE. I am not sure of this thing. But I remember one time I was not able to run the application: set up in Eclipse and running properly, in Netbeans. Please help me understand this. TIA

[Vijitha Kumara]

However I have one more query related to the directory structure and places where you need to put the various descriptors, context files etc. If we are using Eclipse as IDE - will the package hierarchy be same for Netbeans IDE.

Placing those descriptors, config files in standard places matters when you deploy in an application server/running as a standalone app etc.. and not with development. Different IDEs use different folder hierarchies when we create projects (web,Java projects etc...). But the IDE will package the fles in a way that can be run (and accepted) in an application server (for web projects etc..). We can even use our own hierarchies and build the output files (to be run in a server/standalone) by using build tools like Ant inside the IDEs.