<?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>
    <property name="connection.datasource">java:comp/env/jdbc/Test</property>
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
    <property name="hibernate.show_sql">true</property>
    <property name="hibernate.current_session_context_class">thread</property>

    <property name="hibernate.hbm2ddl.auto">create-drop</property>
    <property name="hibernate.format_sql">true</property>
    <mapping class="com.vo.entity.Group"/>
    <mapping class="com.vo.entity.GroupAddress"/>
    <mapping class="com.vo.entity.GroupUsers"/>
    <mapping class="com.vo.entity.User"/>
   <!-- Similarly more mapping classes/-->
  </session-factory>
</hibernate-configuration>

java.lang.NoSuchMethodError: org.hibernate.util.ReflectHelper.classForName(Ljava/lang/String;Ljava/lang/Class;)Ljava/lang/Class;
        at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:800)
        at com.util.db.hibernate.HibernateUtil.<clinit>(HibernateUtil.java:27)
        at com.util.db.UserDB.insertUser(UserDB.java:50)

public class HibernateUtil {
    private static final SessionFactory sessionFactory;

    static {
        try {
            // Create the SessionFactory from standard (hibernate.cfg.xml)
            // config file.
            sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
        } catch (Throwable ex) {
            // Log the exception.
            System.err.println("Initial SessionFactory creation failed." + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static Session getSession()
            throws HibernateException {
        return sessionFactory.openSession();
    }

}