Hibernate对于commit方法处报 java.lang.NullPointerException 。

 1 public int updateEmp(Emp emp) {
 2 Transaction tx; 
 3         Session    session =  Sft.getSessionfaFactory().openSession();
 4         try {
 5             //session打开旳事物必须放在事物对象      中以便下面操作否则报空指针异常
 6             tx=session.beginTransaction();
 7             session.update(emp);
 8             tx.commit();
 9             return 1;
10         } catch (HibernateException e) {
11             tx.rollback();
12             e.printStackTrace();
13             return 0;
14         } finally{
15             Sft.closeSession();
16         } 

 1 public int addEmp(Emp emp) {
 2         Session    session =  Sft.getSessionfaFactory().openSession();
 3         try {
 4             session.beginTransaction();
 5             session.save(emp);
 6             //tx.commit();
 7             session.getTransaction().commit();
 8             return 1;
 9         } catch (HibernateException e) {
10             session.getTransaction().rollback();
11             e.printStackTrace();
12             return 0;
13         } finally{
14             Sft.closeSession();
15         } 

 1 <many-to-one name="dept" class="cn.entity.Dept" lazy="false" cascade="save-update"
 2  column="dno" />
 3 
 4 
 5 
 6 
 7 
 8 
 <set name="emps" lazy="false" cascade="save-update" >
        <key column="dno"/>
        <one-to-many  class="cn.entity.Emp"/>
        </set>