请问老师Unknown entity: cqu.edu.entity.Students怎么解决呢

Question

测试类：@Test public void testSaveStudent(){ Configuration cfg = new Configuration();        cfg.configure(); Session session = MyHibernateSessionFactory.getSessionFactory().getCurrentSession(); session.beginTransaction(); Transaction tx=session.beginTransaction();        // cfg.addClass(cqu.edu.entity.Students.class);  Students student1=new Students("S0000001","张三","男",new Date(),"重庆"); Students student2=new Students("S0000002","李四","男",new Date(),"海南"); Students student3=new Students("S0000003","王五","男",new Date(),"四川"); session.save(student1); session.save(student2); session.save(student3); tx.commit();}hibernate.cfg.xml文件：<?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.username">root</property>     <property name ="connection.password">123456</property>     <property name= "connection.driver_class">com.mysql.jdbc.Driver </property >      <!-- 驱动路径 -->      <property name= "connection.url">jdbc:mysql://127.0.0.1:3306/students_database?useUnicode=true&amp;characterEncoding=UTF-8</property ><!-- 连接数据库字符串 -->       <property name= "hibernate.dialect">org.hibernate.dialect.MySQLDialect</property >      <property name ="show_sql">true</property>     <!-- 显示SQL语句 -->       <property name ="format_sql">true</property>       <property name ="hbm2ddl.auto">update</property>                <!-- 配置使用session.getCurrentSession()方法 -->     <property name= "hibernate.current_session_context_class" >thread</property >      <property name="javax.persistence.validation.mode">none</property>      <!-- hbm.xml -->     <mapping resource ="cqu/edu/entity/Users.hbm.xml"/> <mapping resource ="cqu/edu/entity/yStudents.hbm.xml"/>        </session-factory > </hibernate-configuration>   相应的Students.hbm.xml文件：<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-mapping PUBLIC       "-//Hibernate/Hibernate Mapping DTD 3.0//EN"      "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping>   <class name="cqu.edu.entity.Students" table="STUDENTS">   <id name="sid" type="java.lang.String"  length="8">   <generator class="assigned"/>   </id>   <property name="sname" type="java.lang.String"></property>   <property name="gender" type="java.lang.String"></property>   <property name="birthday" type="java.util.Date"></property>   <property name="address" type="java.lang.String"></property>       </class></hibernate-mapping>  谢谢！