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新建的对象立马被删除
@Test
public void testDelete() {
Teacher t = new Teacher();
t.setName("t1");
t.setTitle("middle");
t.setBirthDate(new Date());
Session session = sessionFactory.getCurrentSession();
session.beginTransaction();
session.save(t);
System.out.println(t.getId());
session.getTransaction().commit();
Session session2 = sessionFactory.getCurrentSession();
session2.beginTransaction();
session2.delete(t);
session2.getTransaction().commit();
}
删除指定ID的对象:
@Test
public void testDelete2() {
Teacher t = new Teacher();
t.setId(2);
Session session2 = sessionFactory.getCurrentSession();
session2.beginTransaction();
session2.delete(t);
session2.getTransaction().commit();
}
load返回的代理对象, 真正用到对象时才发出sql语句,
get直接从数据库加载,发出sql语句, 不会延迟.
所以load必须在commit之前执行getName方法的操作.
但是get放在commit之前之后都可以.
@Test
public void testLoad() {
Session session = sessionFactory.getCurrentSession();
session.beginTransaction();
Teacher t = (Teacher)session.load(Teacher.class, 1); //此数字是ID
System.out.println(t.getName());
session.getTransaction().commit();
//System.out.println(t.getClass());
}
@Test
public void testGet() {
Session session = sessionFactory.getCurrentSession();
session.beginTransaction();
Teacher t = (Teacher)session.get(Teacher.class, 1);
session.getTransaction().commit();
//System.out.println(t.getClass());
System.out.println(t.getName());
}
update:
第一种情况: 用给的detached对象来更新persistent对象.
@Test
public void testUpdate1() {
Session session = sessionFactory.getCurrentSession();
session.beginTransaction();
Teacher t = (Teacher)session.get(Teacher.class, 1); //persistent
session.getTransaction().commit();
t.setName("zhanglaoshi"); //commit后, detached
Session session2 = sessionFactory.getCurrentSession();
session2.beginTransaction();
session2.update(t); //persistent
session2.getTransaction().commit();
}
第二种情况:更新transient对象会报错
@Test
public void testUpdate2() {
Teacher t = new Teacher();
t.setName("zhanglaoshi");
Session session2 = sessionFactory.getCurrentSession();
session2.beginTransaction();
session2.update(t);
session2.getTransaction().commit();
}
第三种情况, 手动设置ID后update, 数据库有对应记录
@Test
public void testUpdate3() {
Teacher t = new Teacher();
t.setId(3);
t.setName("zhanglaoshi");
Session session2 = sessionFactory.getCurrentSession();
session2.beginTransaction();
session2.update(t);
session2.getTransaction().commit();
}
第四种情况: 我们在update的时候, 没有设置别的字段, 但是控制台把所有字段都输出了,效率低下.
一个persistent状态的对象只要设定不同字段, 就会更新:
@Test
public void testUpdate4() {
Session session = sessionFactory.getCurrentSession();
session.beginTransaction();
Teacher t = (Teacher)session.get(Teacher.class, 1); //Persistent状态
t.setName("zhangsan2"); //缓存和数据库内容不一致, commit时统一
session.getTransaction().commit();
}
最后都没有得到我们想要的效果: 只更新想改变的字段, 有3种方法:
1. xml和annotation设置
annotation方法:Teacher.java里不想更新的字段的get方法前,加入@Column(updatable=false)
xml方法: <property name="title" update=false> </property>
2. 使用xml的dynamic-update,
<hibernate-mapping> <class name="com.bjsxt.hibernate.Student" dynamic-update="true">
3. 推荐!!! HQL (EJBQL)
注意: update后面的Student是对象, 不是表名
@Test
public void testUpdate7() {
Session session = sessionFactory.getCurrentSession();
session.beginTransaction();
Query q = session.createQuery("update Student s set s.name=‘z5‘ where s.id = 1");
q.executeUpdate();
session.getTransaction().commit();
}
hibernate--session的CRUD方法, delete, load,get,update
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原文地址：http://www.cnblogs.com/wujixing/p/5416867.html
