初学hibernate 第一个小程序后台没有报错，但是数据添加不成功？！
/*测试类*/
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

import tang.deng.ke.model.Student;


public class TestStudent {
public static void main(String args[]){
Student s = new Student();
s.setId(1);
s.setName("s1");
s.setAge(20);
Configuration cfg = new Configuration();
SessionFactory sf = cfg.configure().buildSessionFactory();
Session session = sf.openSession();
session.beginTransaction();
session.save(s);
session.getTransaction();
session.close();
sf.close();
}
}
/* 实体类如下*/


package tang.deng.ke.model;

public class Student {
private int age;

private int id;

private String name;

public int getAge() {
return age;
}

public int getId() {
return id;
}

public String getName() {
return name;
}

public void setAge(int age) {
this.age = age;
}

public void setId(int id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}

}

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>

  <!-- Database connection settings -->
  <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
  <property name="connection.url">jdbc:mysql://localhost/hibernate</property>
  <property name="connection.username">root</property>
  <property name="connection.password">tom</property>

  <!-- JDBC connection pool (use the built-in) -->
  <!-- <property name="connection.pool_size">1</property> -->

  <!-- SQL dialect -->
  <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

  <!-- Enable Hibernate's automatic session context management -->
  <property name="current_session_context_class">thread</property>

  <!-- Disable the second-level cache -->
  <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>

  <!-- Echo all executed SQL to stdout -->
  <property name="show_sql">true</property>

  <!-- Drop and re-create the database schema on startup -->
  <!-- <property name="hbm2ddl.auto">update</property> -->
 
  <mapping resource="tang/deng/ke/model/Student.hbm.xml"/>

  </session-factory>

</hibernate-configuration>



/* Student.hbm.xml 如下*/

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
  "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
  "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="tang.deng.ke.model">
<class name="Student">
<id name="id"></id>
<property name=&qu