在PluralSight上学习“Hibernate入门”教程时，我遇到了这个异常错误。完整的错误如下：

Exception in thread "main" org.hibernate.MappingException: Unknown entity: com.simpleprogrammer.User
    at org.hibernate.internal.SessionFactoryImpl.getEntityPersister(SessionFactoryImpl.java:776)
    at org.hibernate.internal.SessionImpl.getEntityPersister(SessionImpl.java:1451)
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:100)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:192)
    at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:38)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:177)
    at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:32)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
    at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:678)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:670)
    at org.hibernate.internal.SessionImpl.save(SessionImpl.java:665)
    at com.simpleprogrammer.Program.main(Program.java:15)

不确定是什么问题。我创建了User.java pojo。我创建了一个与pojo匹配的表。我创建了Map，然后将Map添加到hibernate.cfg.xml文件中。但是，仍然出现错误。有人能帮助我解决这个问题吗？
hibernate.cfg.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
                                         "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
 <session-factory name="">
  <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
  <property name="hibernate.connection.url">jdbc:mysql://localhost:3306</property>
  <property name="hibernate.connection.username">root</property>
  <property name="hibernate.default_schema">protein_tracker</property>
  <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
  <mapping class="com.simpleprogrammer.User" resource="com/simpleprogrammer/User.hbm.xml"/>
 </session-factory>
</hibernate-configuration>

Program.java

public class Program {
    public static void main(String[] args) {
        System.out.println("Hello World!");
        Session session = HibernateUtilities.getSessionFactory().openSession();
        session.beginTransaction();

        User user = new User();
        user.setName("Joe");
        user.setGoal(250);
        session.save(user);

        session.getTransaction().commit();
        session.close();
        HibernateUtilities.getSessionFactory().close();
    }
}

User.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated Oct 17, 2015 11:44:47 AM by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>
    <class name="com.simpleprogrammer.User" table="USERS">
        <id name="id" type="int">
            <column name="ID" />
            <generator class="identity" />
        </id>
        <property name="name" type="java.lang.String">
            <column name="NAME" />
        </property>
        <property name="total" type="int">
            <column name="TOTAL" />
        </property>
        <property name="goal" type="int">
            <column name="GOAL" />
        </property>
    </class>
</hibernate-mapping>

User.java

package com.simpleprogrammer;

public class User {
    private int id;
    private String name;
    private int total;
    private int goal;

    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getTotal() {
        return total;
    }
    public void setTotal(int total) {
        this.total = total;
    }
    public int getGoal() {
        return goal;
    }
    public void setGoal(int goal) {
        this.goal = goal;
    }
}

HibernateUtilities.java

package com.simpleprogrammer;

import org.hibernate.HibernateException;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class HibernateUtilities {

    private static SessionFactory sessionFactory;
    private static ServiceRegistry serviceRegistry;

    static {
        try {
            Configuration configuration = new Configuration().configure();

            serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
            sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        }
        catch(HibernateException exception) {
            System.out.println("Problem creating session factory!");
        }   
    }

    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}