Getting ClassCastException while building the Hibernate Session Factory

[rakesh kadulkar]

Hi,

I am getting ClassCastException while building the hibernate session factory.
The hibernate session factory gets built without any error on my local setup which is exactly same as prod setup.
However this error does not occures always. The hibernate session factory gets built always but sometimes I get to see this error in the tomcat logs and thus my application stops working.
As a workaround we take a reboot on the tomcat server and the problem gets solved.
Below is the code I use for getting sessions from the session factory.

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;

/**
 * Configures and provides access to Hibernate sessions, tied to the
 * current thread of execution.  Follows the Thread Local Session
 * pattern, see {@link http://hibernate.org/42.html }.
 */
public class HibernateSessionFactory {

    /** 
     * Location of hibernate.cfg.xml file.
     * Location should be on the classpath as Hibernate uses  
     * #resourceAsStream style lookup for its configuration file. 
     * The default classpath location of the hibernate config file is 
     * in the default package. Use #setConfigFile() to update 
     * the location of the configuration file for the current session.   
     */
    private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";
	private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
    private  static Configuration configuration = new Configuration();    
    private static org.hibernate.SessionFactory sessionFactory;
    private static String configFile = CONFIG_FILE_LOCATION;

	static {
    	try {
			configuration.configure(configFile);
			sessionFactory = configuration.buildSessionFactory();
		} catch (Exception e) {
			System.err
					.println("%%%% Error Creating SessionFactory %%%%");
			e.printStackTrace();
		}
    }
    private HibernateSessionFactory() {
    }
	
	/**
     * Returns the ThreadLocal Session instance.  Lazy initialize
     * the <code>SessionFactory</code> if needed.
     *
     *  @return Session
     *  @throws HibernateException
     */
    public static Session getSession() throws HibernateException {
        Session session = (Session) threadLocal.get();

		if (session == null || !session.isOpen()) {
			if (sessionFactory == null) {
				rebuildSessionFactory();
			}
			session = (sessionFactory != null) ? sessionFactory.openSession()
					: null;
			threadLocal.set(session);
		}

        return session;
    }

	/**
     *  Rebuild hibernate session factory
     *
     */
	public static void rebuildSessionFactory() {
		try {
			configuration.configure(configFile);
			sessionFactory = configuration.buildSessionFactory();
		} catch (Exception e) {
			System.err
					.println("%%%% Error Creating SessionFactory %%%%");
			e.printStackTrace();
		}
	}

	/**
     *  Close the single hibernate session instance.
     *
     *  @throws HibernateException
     */
    public static void closeSession() throws HibernateException {
        Session session = (Session) threadLocal.get();
        threadLocal.set(null);

        if (session != null) {
            session.close();
        }
    }

	/**
     *  return session factory
     *
     */
	public static org.hibernate.SessionFactory getSessionFactory() {
		return sessionFactory;
	}

	/**
     *  return session factory
     *
     *	session factory will be rebuilded in the next call
     */
	public static void setConfigFile(String configFile) {
		HibernateSessionFactory.configFile = configFile;
		sessionFactory = null;
	}

	/**
     *  return hibernate configuration
     *
     */
	public static Configuration getConfiguration() {
		return configuration;
	}

}

The exception I receive in the logs is

%%%% Error Creating SessionFactory %%%%
java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String
	at org.hibernate.util.PropertiesHelper.resolvePlaceHolders(PropertiesHelper.java:88)
	at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1173)
	at com.yyyyy.services.HibernateSessionFactory.<clinit>(HibernateSessionFactory.java:31)
	at com.yyyy.servlet.ValidateServlet.doPost(ValidateServlet.java:54)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
	at java.lang.Thread.run(Unknown Source)
%%%% Error Creating SessionFactory %%%%
org.hibernate.MappingException: Could not read mappings from resource: File.hbm.xml
	at org.hibernate.cfg.Configuration.addResource(Configuration.java:485)
	at org.hibernate.cfg.Configuration.parseMappingElement(Configuration.java:1465)
	at org.hibernate.cfg.Configuration.parseSessionFactory(Configuration.java:1433)
	at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1414)
	at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1390)
	at org.hibernate.cfg.Configuration.configure(Configuration.java:1310)
	at com.yyyy.services.HibernateSessionFactory.rebuildSessionFactory(HibernateSessionFactory.java:69)
	at com.yyyy.services.HibernateSessionFactory.getSession(HibernateSessionFactory.java:53)
	at com.yyyy.servlet.ValidateServlet.doPost(ValidateServlet.java:54)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
	at java.lang.Thread.run(Unknown Source)
Caused by: org.hibernate.DuplicateMappingException: Duplicate class/entity mapping com.yyyy.transcript.File
	at org.hibernate.cfg.Mappings.addClass(Mappings.java:118)
	at org.hibernate.cfg.HbmBinder.bindRoot(HbmBinder.java:154)
	at org.hibernate.cfg.Configuration.add(Configuration.java:386)
	at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:427)
	at org.hibernate.cfg.Configuration.addResource(Configuration.java:482)
	... 22 more

I don't understand why this is happening. The same tomcat also runs some other applications.
Can this be due to some other application. This is just a guess. I am not sure of this.

Further in the exception logs provided above, I see a statement saying

Could not read mappings from resource: File.hbm.xml
and
Duplicate class/entity mapping com.yyyy.transcript.File

Is it because the HibernateSessionFactory.class may be calling a rebuildSessionFactory method().

Your help in this regard is very much appreciated.

Thanks
Rakesh