关于hibernate空指针异常的问题

Question

import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import org.junit.Test;import com.opensymphony.xwork2.interceptor.annotations.After;import com.opensymphony.xwork2.interceptor.annotations.Before;public class HibernateUtil { private SessionFactory sessionFactory; private Session session; private Transaction transaction; @Before public void init() { // 创建配置对象 Configuration config = new Configuration().configure(); // 创建回话工厂对象 sessionFactory = config.buildSessionFactory(); // 会话对象 session = sessionFactory.openSession(); // 开启事务 transaction = session.beginTransaction(); } @After public void destory() { transaction.commit();// 提交事务 session.close();// 关闭会话 sessionFactory.close();// 关闭会话工厂 } @Test public void testSaveUser(){ User u=(User)session.get(User.class, 100000); System.out.println(u.getUsername()); }} 大佬们，求解为什么会出现java.lang.NullPointerException，提示是User u=(User)session.get(User.class, 100000);这个地方出错，但是我排查不出来。。