hibernate的三种查询方式
来源:互联网 发布:程朱理学知乎 编辑:程序博客网 时间:2024/05/02 11:13
Hibernate的查询方式
一、HQL查询
• HQL(Hibernate Query Language)提供了丰富灵活的查询方式,使用HQL进行查询也是Hibernate官方推荐使用的查询方式。
• HQL在语法结构上和SQL语句十分的相同,所以可以很快的上手进行使用。使用HQL需要用到Hibernate中的Query对象,该对象专门执行HQL方式的操作。
查询所有示例12345678
session.beginTransaction();String hql = "from User"; // from 后跟的是要查询的对象,而不是表Query query = session.createQuery(hql);List<User> userList = query.list();for(User user:userList){ System.out.println(user.getUserName());}session.getTransaction().commit();
带where的查询示例
1234567891011121314151617181920
session.beginTransaction();String hql = "from User where userName = 'James'";Query query = session.createQuery(hql);List<User> userList = query.list();for(User user:userList){ System.out.println(user.getUserName());}session.getTransaction().commit();/* 在HQL中where语句中使用的是持久化对象的属性名,如上面示例中的userName。当然在HQL中也可以使用别名*/String hql = "from User as u where u.userName = 'James'";/*过滤条件 在where语句中还可以使用各种过滤条件,如:=、<>、<、>、>=、<=、between、not between、in、not in、is、like、and、or等*/
获取一个不完整的对象
12345678910111213141516171819202122
session.beginTransaction();String hql = "select userName from User";Query query = session.createQuery(hql);List<Object> nameList = query.list();for(Object obj:nameList){
String name=(String)obj;
System.out.println(name);}session.getTransaction().commit();// 多个属性的话,需要用object[]接收session.beginTransaction();String hql = "select userName,userPwd from User";Query query = session.createQuery(hql);List nameList = query.list();for(Object obj:nameList){ Object[] array = (Object[]) obj; // 转成object[] System.out.println("name:" + array[0]); System.out.println("pwd:" + array[1]);}session.getTransaction().commit();
统计和分组查询
12345678910111213141516171819
session.beginTransaction();String hql = "select count(*),max(id) from User";Query query = session.createQuery(hql);List nameList = query.list();for(Object obj:nameList){ Object[] array = (Object[]) obj; System.out.println("count:" + array[0]); System.out.println("max:" + array[1]);}session.getTransaction().commit();/* 该条sql语句返回的是单条数据,所以还可以这样写 单列数据用Object,多列数据用Object[]*/Object[] object = (Object[]) query.uniqueResult();System.out.println("count:" + object[0]);System.out.println("max:" + object[1]);
更多写法
1234567
select distinct name from Student;select max(age) from Student;select count(age),age from Student group by age;from Student order by age;
HQL占位符
123456789101112
session.beginTransaction();String hql = "from User where userName = ?";Query query = session.createQuery(hql);// 索引从0开始 query.setString(0, "James");List<User> userList = query.list();for(User user:userList){ System.out.println(user.getUserName());}session.getTransaction().commit();
HQL引用占位符
12345678910111213
session.beginTransaction();String hql = "from User where userName = :name";Query query = session.createQuery(hql);query.setParameter("name", "James");List<User> userList = query.list();for(User user:userList){ System.out.println(user.getUserName());}session.getTransaction().commit();
123456789101112
session.beginTransaction();String hql = "from User";Query query = session.createQuery(hql);query.setFirstResult(0);query.setMaxResults(2);List<User> userList = query.list();for(User user:userList){ System.out.println(user.getUserName());}session.getTransaction().commit();
二、QBC(Query By Criteria)查询
• Criteria对象提供了一种面向对象的方式查询数据库。Criteria对象需要使用Session对象来获得。
• 一个Criteria对象表示对一个持久化类的查询。
查询所有1234567891011
session.beginTransaction();Criteria c = session.createCriteria(User.class);List<User> userList = c.list();for(User user:userList){ System.out.println(user.getUserName());}session.getTransaction().commit();
where
1234567891011
session.beginTransaction();Criteria c = session.createCriteria(User.class);c.add(Restrictions.eq("userName", "James"));List<User> userList = c.list();for(User user:userList){ System.out.println(user.getUserName());}session.getTransaction().commit();
Restrictions对象
123456789101112
方法名称 对应SQL中的表达式----------------------------------------------------------Restrictions.eq field = valueRestrictions.gt field > valueRestrictions.lt field < valueRestrictions.ge field >= valueRestrictions.le field <= valueRestrictions.between field between value1 and value2Restrictions.in field in(…)Restrictions.and andRestrictions.or orRestrictions.like field like value
123456
Criteria c = session.createCriteria(User.class);c.add(Restrictions.like("userName", "J"));c.add(Restrictions.eq("id", 120));c.add(Restrictions.or(Restrictions.eq("userName", "James"), Restrictions.eq("userName", "Alex")));
12345678910
session.beginTransaction();Criteria c = session.createCriteria(User.class);c.add(Restrictions.eq("id", 120));User user = (User) c.uniqueResult();System.out.println(user.getUserName());session.getTransaction().commit();
分页
1234
Criteria c = session.createCriteria(User.class);c.setFirstResult(0);c.setMaxResults(5);
分组与统计
12345678910
session.beginTransaction();Criteria c = session.createCriteria(User.class);c.setProjection(Projections.sum("id"));Object obj = c.uniqueResult();System.out.println(obj);session.getTransaction().commit();
123456789
方法名称 描述-------------------------------------------------------Projections.sum 等于SQL中聚合函数sumProjections.avg 等于SQL中聚合函数avgProjections.count 等于SQL中聚合函数countProjections .distinct 去除重复记录Projections.max 等于SQL中聚合函数maxProjections.min 等于SQL中聚合函数minProjections .groupProperty 对指定的属性进行分组查询
多个统计与分组
1234567891011121314
session.beginTransaction();Criteria c = session.createCriteria(User.class);ProjectionList projectionList = Projections.projectionList();projectionList.add(Projections.sum("id"));projectionList.add(Projections.min("id"));c.setProjection(projectionList);// 和HQL一样,单列用Object,多列用Object[] Object[] obj = (Object[]) c.uniqueResult();System.out.println("sum:" + obj[0]);System.out.println("min:" + obj[1]);
排序
123
Criteria c = session.createCriteria(User.class);c.addOrder(Order.desc("id"));
三、原生SQL查询:
示例123456789101112
session.beginTransaction();String sql = "select id,username,userpwd from t_user";List list = session.createSQLQuery(sql).list();for(Object item : list){ Object[] rows = (Object[]) item; System.out.println("id:" + rows[0] + "username:" + rows[1] + "userpwd:" + rows[2]);}session.getTransaction().commit();
addEntity()示例
1234567891011121314
session.beginTransaction();String sql = "select id,username,userpwd from t_user";// addEntity()可以告诉Hibernate你想要封装成对象的类型,然后自动为你封装SQLQuery query = session.createSQLQuery(sql).addEntity(User.class);List<User> list = query.list();for(User user : list){ System.out.println(user.getUserName());}session.getTransaction().commit();
uniqueResult示例
12345678910
session.beginTransaction();String sql = "select id,username,userpwd from t_user where id = 2";SQLQuery query = session.createSQLQuery(sql).addEntity(User.class);User user = (User) query.uniqueResult();System.out.println(user.getUserName());session.getTransaction().commit();
- hibernate的三种查询方式
- hibernate的三种查询方式
- hibernate的三种查询方式
- Hibernate的三种查询方式
- Hibernate的三种查询方式
- hibernate 三种常用的查询方式
- Hibernate查询数据库的三种方式
- Hibernate的三种查询方式
- Hibernate的三种查询方式
- hibernate的三种查询方式
- hibernate 三种查询方式
- hibernate三种查询方式
- Hibernate 三种查询方式
- hibernate 三种查询方式
- hibernate三种查询方式
- Hibernate 的三种查询方式:HQL、Criteria、Sql
- Hibernate 的三种查询方式:HQL、Criteria、Sql
- Hibernate 的三种查询方式:HQL、Criteria、Sql
- Oracle实例与数据库的概念详细解释
- 在你的web页面中使用JSXGraph
- [Android源码分析]bluez internal event的处理
- 给C#2010程序添加图标
- js正则表达式校验是否是合法数字
- hibernate的三种查询方式
- [LeetCode] Next Permutation
- 风雨20年:我所积累的20条编程经验
- Protege4学习笔记(一)---本体定义及相关概念
- Keepalived+Nginx实现高可用和双主节点负载均衡
- Android 在xml中配置 float 和 integer 值
- SQL防注入
- 获取文件或者字符的MD5值
- Android开发规范