出现一个错误

package com.hanqi.test;
import java.util.Date;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.hanqi.entity.User;

public class Test01 {
    private SessionFactory sf;
    private Session se;
    private Transaction ts;
    //在测试用例方法被执行之前自动执行方法
    //一般用来初始化公用的对象
    @Before
    public void  init()
    {
        //1获取配置文件
        Configuration cfg=new Configuration().configure();
                
        //2注册配置
        ServiceRegistry sr=new StandardServiceRegistryBuilder().applySettings(cfg.getProperties()).build();
                    
        //3获取SessionFactory(相当于JDBC)
        sf =cfg.buildSessionFactory(sr);        
        System.out.println(sf);
                
        //4产生session  生成会话
        se=sf.openSession();
                
        //5启动事物
        ts=se.beginTransaction();
    }
    //后知方法
    @After
    public void detory()
    {        
        //7提交事务
        ts.commit();
        
        //8释放资源
        se.close();        
        sf.close();
    }
    //测试Hibernate连接数据库
    
    @Test
    public void test() 
    {
                
        //6操作数据库
        //（1）添加数据
        //实例化的新对象，处于临时状态
        User u1=new User();
        u1.setBirthday(new Date());
        u1.setMoney(2000);
        u1.setPassword("123456");
        u1.setUserName("恩恩");
        //（2）保存数据
        //通过save方法吧对象从临时状态转成持久化状态
        se.save(u1).toString();
    }
    @Test
    public void test1()
    {    
        //查询数据
        //提供两个参数
        //1需要返回哪一个持久化类的实例
        //2实例的标识(数据的主键值)
        //通过Session的get方法获得的对象处于持久化状态
        User u2=(User)se.get(User.class, 1);
        
        //修改
        u2.setUserName("庚衣");
        
        System.out.println(u2);
        
        //删除
        se.delete(u2);        //持久化对象进入删除状态
    }
    @Test
    public void test02()
    {
        User u1 =(User)se.get(User.class, 4);    //get立即加载
        System.out.println("get后");
        System.out.println(u1);
    }
    
    @Test
    public void test03()
    {
        User u1 =(User)se.load(User.class, 4);   //load延迟加载     懒加载
        System.out.println("load后");
        System.out.println(u1);                     //当使用是再加载
    }
    //测试游离状态
    @Test
    public void Test04()
    {
        //得到持久化状态
        User u1 =(User)se.load(User.class, 7);
        System.out.println(u1);
        //关闭Session
        se.close();
        //使u1进入游离状态
        u1.setUserName("李白");
        //把OID换成null
        u1.setUserID(null);
        System.out.println("重新设置Session事物");
        //从新创建session
        se=sf.openSession();
        //重新开启事物
        ts=se.beginTransaction();
        //
        se.saveOrUpdate(u1);
        //使用save
        //se.update(u1);
        System.out.println(u1);
    }
}

package com.hanqi.entity;
//持久化类

import java.util.Date;

public class User 
{
    private Integer userID;    
    private String userName;
    private Date birthday;
    private double money;
    private String password;
    
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    public Integer getUserID() {
        return userID;
    }
    public void setUserID(Integer userID) {
        this.userID = userID;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }
    public double getMoney() {
        return money;
    }
    public void setMoney(double money) {
        this.money = money;
    }
    public User() {
        super();
    }
    public User(Integer userID, String userName, Date birthday, double money) {
        super();
        this.userID = userID;
        this.userName = userName;
        this.birthday = birthday;
        this.money = money;
    }
    @Override
    public String toString() {
        return "User [userID=" + userID + ", userName=" + userName + ", birthday=" + birthday + ", money=" + money
                + ", password=" + password + "]";
    }    
}

<?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 >
  <!-- 数据库连接 -->
  <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
  <property name="hibernate.connection.password">123</property>
  <property name="hibernate.connection.url">jdbc:oracle:thin:@localhost:1521:orcl</property>
  <property name="hibernate.connection.username">test0816</property>
  <!-- 数据库方案 -->
  <property name="hibernate.default_schema">TEST0816</property>
  <!-- 数据库方言 -->
  <property name="hibernate.dialect">org.hibernate.dialect.Oracle10gDialect</property>
  <!-- 调试 -->
  <property name="hibernate.show_sql">true</property>
  <property name="hibernate.format_sql">true</property>
  <!-- 自动见表方法 -->
  <property name="hibernate.hbm2ddl.auto">update</property>
  <!-- 映射文件-->
  <mapping resource="com/hanqi/entity/User.hbm.xml"/>
 </session-factory>
</hibernate-configuration>

<?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 2016-11-7 14:41:21 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping>
    <class name="com.hanqi.entity.User" table="T_USER">
        <id name="userID" type="java.lang.Integer">
            <column name="USERID" />
            <generator class="native" />
        </id>
        <property name="userName" type="java.lang.String">
            <column name="USERNAME" length="20" not-null="true" unique="true"/>
        </property>
        <property name="birthday" type="java.util.Date">
            <column name="BIRTHDAY" />
        </property>
        <property name="money" type="double">
            <column name="MONEY" length="8" scale="2" sql-type="NUMBER" default="0"/>
        </property>
        <property name="password" type="java.lang.String">
                <column name="PASSWORD"  length="10"/>
           </property>
    </class>
</hibernate-mapping>

当在测试test04时出现错误了！！！！！！！！！！！！！！！！！1

十一月 08, 2016 4:28:58 下午 org.hibernate.AssertionFailure <init>
ERROR: HHH000099: an assertion failure occured (this may indicate a bug in Hibernate, but is more likely due to unsafe use of the session): org.hibernate.AssertionFailure: null identifier
十一月 08, 2016 4:28:58 下午 org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop
INFO: HHH000030: Cleaning up connection pool [jdbc:oracle:thin:@localhost:1521:orcl]