Hibernate中对增删改查的小结
Hibernate中对增删改查的小结
mysql中库表News,字段如下
id????? |? int???? |? auto_increment? |? primary key
title?? |? varchar
content |? varchar
date??? |? varchar
1：Hibernate的insert操作
????????Session session = HibernateSessionFactory.getSession();
????????
????????News news = new News();
????????news.setContent("my content");
????????news.setTitle("my title");
????????news.setDate("my date"); //news是VO
????????
????????Transaction trans = session.beginTransaction();
????????session.save(news); //news是PO
????????trans.commit();???? //任何有关数据库更新的操作都是commit后进数据库的
??? ??? HibernateSessionFactory.closeSession();
2：Hibernate的update操作
????????Session session = HibernateSessionFactory.getSession();
????????News news = new News();
????????news.setId(103);? //id不可少，Hibernate只通过id来查找数据库
????????news.setContent("update content");
????????news.setTitle("update title");
????????
????????Transaction trans = session.beginTransaction();
????????session.update(news);
????????trans.commit();
??? ??? HibernateSessionFactory.closeSession();
注意这里我们更新数据不想对date进行更新，所以没写 setDate ，但Hibernate会认为我们是想把date设置为null，所以如果要更新表中一些字段，最好用下面的方法。
????????Session session = HibernateSessionFactory.getSession();
????????Transaction trans = session.beginTransaction();
????????News news = (News)session.get(News.class, 103);? //*****(1)
????????news.setDate("update date");? //*****(2)
????????session.save(news);? //*****(3)
????????trans.commit();
??? ??? HibernateSessionFactory.closeSession();
这里其实对数据库进行了两次操作，(1)时从数据库中把相应纪录查找出来，这里news是一个PO，(2)对PO进行date的更新，其他数据没变，然后(3)保存，由于(1)查出的数据就有title,content，所以保存时候title和content都不会是null。
3：Hibernate的delete操作
????????Session session = HibernateSessionFactory.getSession();
????????Transaction trans = session.beginTransaction();
????????News news = new News();
????????news.setId(8);? //用下面那句效果一样，只是多了句select
//????? News news = (News)session.get(News.class, 8);
????????session.delete(news);
????????trans.commit();
??? ??? HibernateSessionFactory.closeSession();
使用hql来删除(可作批量删除)
??? ??? Session session = HibernateSessionFactory.getSession();
????????String hql = "delete Billdetail where name>'detailName1'";
????????Query query = session.createQuery(hql);
????????int ref = query.executeUpdate();
????????session.beginTransaction().commit();
????????System.out.println("delete dates=>"+ref); //操作条数
????????session.close();
4：Hibernate的select操作
Hibernate的select操作非常丰富，这里写常用的：
1.criteria查询
????????Session session = HibernateSessionFactory.getSession();
????????Criteria c = session.createCriteria(News.class);//News是类，所以N大写
????????c.add(Expression.lt("date", "date5"));
????????c.add(Expression.between("date", "date1", "date8"));
????????c.addOrder(Order.desc("date"));
????????List<News> list = c.list();
????????for(int i=0;i<list.size();i++)
????????{
????????????System.out.println(list.get(i).getId()+":"+list.get(i).getDate());
????????}
??? ??? HibernateSessionFactory.closeSession();
比较符合面向对象的概念，因为库表和JAVA类已经作了映射关系，注意Hibernate的所有操作都是针对JAVA类的，而不是库表，所以要区分大小写。
上面的查询相当于sql是: select * from news where date < 'date5' and date BETWEEN 'date1' and 'date8' ORDER by date desc;
2.HQL查询
????????Query query = session.createQuery("from News ");
????????List<News> list = query.list();? //遍历同上
HQL是Hibernate主推的查询方式，和普通SQL语句也比较接近，但很重要一点不同就是HQL中from后面的是JAVA类名，不是库表名，切忌！！！其它就是如果查询全字段 "select *" 可以省略不写。
当不是查询全字段，或者是从两张表中联合查询数据时，返回的是一个数组：
????????Session session = HibernateSessionFactory.getSession();
????????Query query = session.createQuery("select n.id,n.title,u.username from News as n,User u");
????????List list = query.list();//这里每一行都是一个1维数组
????????for(int i=0;i<list.size();i++)
????????{
????????????Object []o = (Object[])list.get(i);? //转型为数组
????????????int id = (Integer)o[0];? //和select中顺序的类型相对应,可以是类
????????????String title = (String)o[1];
????????????String username = (String)o[2];
????????????System.out.println("id:"+id+" , "+"title"+title+" , "+username);
????????}
??? ??? HibernateSessionFactory.closeSession();
查询结果集的大小(和Hibernate2中稍微有点不同)
(Integer)session.createQuery("select count(*) from User").iterate().next();
3.SqlQuery查询
????????List<News> list = session.createSQLQuery("select * from News").addEntity(News.class).list();?
addEntity 不能忘记，这种查询方式是把查询好的结果放到一个实体中，再遍历操作，不推荐使用。
SqlQuery查询一些字段时候用addScalar:
SQLQuery query = session.createSQLQuery("select id,title from News");
????????query.addScalar("id", Hibernate.INTEGER); ?//注册字段类型，同下
????????query.addScalar("title",new org.hibernate.type.StringType());
????????List list = query.list();
????????for(int i=0;i<list.size();i++)
????????{
????????????Object[] o = (Object[])list.get(i);
????????????int id = (Integer)o[0];
????????????String title = (String)o[1];
????????????System.out.println("id:"+id+" , title:"+title);
????????}
javabean的属性可以作为命名的查询参数(HQL)
????????Session session = HibernateSessionFactory.getSession();
????????Transaction trans = session.beginTransaction()
????????Query query = session.createQuery("from room in class Room where room.name=:a")
????????query.setParameter("a", "room1");? //和prepareStatement相似
??? ??
//???? Room room1 = new Room();?
//???? room1.setName("room1");? ??
//???? Query query = session.createQuery("from room in class Room where room.name=:name");? //如果用javabean设置参数来查询，=:name的name一定和Room中对应
//???? query.setProperties(room1);
???????
????????List<Room> list = query.list();
????????for(int i=0;i<list.size();i++)
????????{
????????????System.out.println(list.get(i).getName()+":"+list.get(i).getDescription());
????????}
????????
????????trans.commit();
????????HibernateSessionFactory.closeSession()