Exception in thread "main" org.hibernate.InvalidMappingException: Could not parse mapping document from resource userdata.hbm.xml

I am trying my first hibernate program and i am getting this error. My program simply enters username, password and email in the database. I have created a POJO user.java, a UserManager.java, and two xml files, one for config and other for hibernate mapping. I have tried on this error for so long and still no solution.

This is my user.java:

package com.csc.training.Twitter;

public class User {

    String username;
    String password;
    String email;
    int user_id;

    public int getUser_id() {
        return user_id;
    }
    public void setUser_id(int user_id) {
        this.user_id = user_id;
    }


    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public String getEmail() {
        return email;
    }
    public void setEmail(String email) {
        this.email = email;
    }   
}

UserManager.java

package com.csc.training.Twitter;

import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.classic.Session;

public class UserManager {

    public void registration() {

    Configuration config=new Configuration();
    config.configure("hibernate.cfg.xml");
    SessionFactory factory=config.buildSessionFactory();

    Session session=factory.openSession();

    Transaction transaction = (Transaction) session.beginTransaction();

    User user = new User(); 

    user.setUsername("fname2");
    user.setPassword("lname2");
    user.setEmail("def@def.def");

    session.persist(user);

    transaction.commit();

    System.out.println("User Id : " + user.getUser_id());

    session.close();
    System.out.println("Employee update successful...");

}

public static void main(String[] args) {
    UserManager um=new UserManager();
    um.registration();
}
}

And these are the xml files..

userdata.hbm.xml:

<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE hibernate-mapping PUBLIC  "-//Hibernate/Hibernate Mapping DTD//EN" "hibernate-mapping-3.0.dtd"> 

<hibernate-mapping>
   <class name="com.csc.training.Twitter.User" table="userdata">
      <id name="user_id">
         <generator class="increment"></generator>
      </id>
    <id name="joined">
         <generator class="assigned"></generator>
     </id>

      <property name="username" column="username" type="string" />
      <property name="password" column="password" type="string" />
      <property name="email" column="email" type="string" />
   </class>

</hibernate-mapping>

hibernate.cfg.xml:

<?xml version="1.0" encoding="utf-8"?>

<!DOCTYPE hibernate-configuration PUBLIC  "-//Hibernate/Hibernate configuration DTD//EN" "hibernate-configuration-3.0.dtd"> 

<hibernate-configuration>
   <session-factory>
   <property name="hibernate.dialect">
      org.hibernate.dialect.MySQLDialect
   </property>
   <property name="hibernate.connection.driver_class">
      com.mysql.jdbc.Driver
   </property>

   <!-- Assume test is the database name -->
   <property name="hibernate.connection.url">
    jdbc:mysql://localhost/twitter
    </property>
    <property name="hibernate.connection.username">
        root
   </property>
   <property name="hibernate.connection.password">
      root
   </property>

   <!-- List of XML mapping files -->
   <mapping resource="userdata.hbm.xml"/>

</session-factory>
</hibernate-configuration>

My database is twitter and the table name is userdata. userdata contains user_id (int, primary key,auto increment), joined(timestamp),username,email,password. Can anyone tell me what the error is? Thank you very much!