Hibernate(十二)Criteria查询
一、简述
Criteria是一种比hql更面向对象的查询方式。Criteria 可使用 Criterion 和 Projection 设置查询条件。可以设置 FetchMode(联合查询抓取的模式 ) ，设置排序方式，Criteria 还可以设置 FlushModel （冲刷 Session 的方式）和 LockMode （数据库锁模式）。
Criteria本身只是查询的容器。Criteria查询又称对象查询
Criteria查询采用面向对象的方式封装查询条件。由Hibernater自动生成SQL查询语句
二、不带查询条件
建立数据表
create table login ( username varchar2(32) primary key, password varchar2(32) not null , age number(3) ); insert into login select '张三','123456',21 from dual union select 'Tom','123123',34 from dual union select 'Jack','12345678',34 from dual union select '李四','qwerty',23 from dual; commit;
建立持久化类和配置文件
Hibernate.cfg.xml配置文件
<?xml version='1.0' encoding='UTF-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="dialect"> org.hibernate.dialect.Oracle9Dialect </property> <property name="connection.url"> jdbc:oracle:thin:@localhost:1521:orcl </property> <property name="connection.username">root</property> <property name="connection.password">root</property> <property name="connection.driver_class"> oracle.jdbc.OracleDriver </property> <property name="show_sql">true</property> <property name="format_sql">true</property> <mapping resource="entity/Login.hbm.xml" /> </session-factory> </hibernate-configuration>
持久化类和配置文件
package entity; public class Login implements java.io.Serializable { // Fields /** * */ private static final long serialVersionUID = 1L; private String username; private String password; private int age; // Constructors /** default constructor */ public Login() { } /** minimal constructor */ public Login(String username, String password) { this.username = username; this.password = password; } /** full constructor */ public Login(String username, String password, int age) { this.username = username; this.password = password; this.age = age; } // Property accessors public String getUsername() { return this.username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return this.password; } public void setPassword(String password) { this.password = password; } public int getAge() { return this.age; } public void setAge(int age) { this.age = age; } }
配置文件Login.hbm.xml
<?xml version="1.0" encoding="utf-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="entity.Login" table="LOGIN" schema="ROOT"> <id name="username" type="java.lang.String"> <column name="USERNAME" length="32" /> <generator class="assigned" /> </id> <property name="password" type="java.lang.String"> <column name="PASSWORD" length="32" not-null="true" /> </property> <property name="age" type="java.lang.Integer"> <column name="AGE" precision="3" scale="0" /> </property> </class> </hibernate-mapping>
测试类:
package demo; import java.util.List; import org.hibernate.Criteria; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; import entity.Login; public class Demo1 { /** * Criteria无查询条件查询所有 */ public static void main(String[] args) { //声明一个集合用来接收结果 List<Login> result=null; //声明SessionFactory SessionFactory factory=null; //声明Session Session session=null; //初始化以上对象 try{ factory=new Configuration().configure().buildSessionFactory(); session=factory.openSession(); //声明Criteria对象传入一个持久化类对象类型 Criteria criteria=session.createCriteria(Login.class); //查询使用list方法 result=criteria.list(); }catch(HibernateException e){ e.printStackTrace(); }finally{ session.close(); factory.close(); } //输出结果 for (Login login : result) { System.out.println("用户名:"+login.getUsername()+" 密码："+login.getPassword()+" 年龄:"+login.getAge()); } } }
结果:
Hibernate: select this_.USERNAME as USERNAME0_0_, this_.PASSWORD as PASSWORD0_0_, this_.AGE as AGE0_0_ from ROOT.LOGIN this_ 用户名:Jack 密码：12345678 年龄:34 用户名:Tom 密码：123123 年龄:34 用户名:李四 密码：qwerty 年龄:23 用户名:张三 密码：123456 年龄:21
三、添加查询条件
3.1、加入一个username的条件
//声明Criteria对象传入一个持久化类对象类型 Criteria criteria=session.createCriteria(Login.class); //添加查询条件 Restrictions.eq是等于的意思，2个参数，第一个为持久化类的属性，第2个为比较的参数值 criteria.add(Restrictions.eq("username", "Tom")); //查询使用list方法 result=criteria.list();
执行的SQL
select this_.USERNAME as USERNAME0_0_, this_.PASSWORD as PASSWORD0_0_, this_.AGE as AGE0_0_ from ROOT.LOGIN this_ where this_.USERNAME=?
3.2、多个查询条件AND--between
//年龄在大于等于25 criteria.add(Restrictions.le("age", 25)); //年龄小于等于23 criteria.add(Restrictions.ge("age", 23));
或者
//年年龄大于23小于25之间的记录 criteria.add(Restrictions.between("age", 23, 25));
执行的SQL
select this_.USERNAME as USERNAME0_0_, this_.PASSWORD as PASSWORD0_0_, this_.AGE as AGE0_0_ from ROOT.LOGIN this_ where this_.AGE<=? and this_.AGE>=?
select this_.USERNAME as USERNAME0_0_, this_.PASSWORD as PASSWORD0_0_, this_.AGE as AGE0_0_ from ROOT.LOGIN this_ where this_.AGE between ? and ?
3.3、多个查询条件或者条件 or
criteria.add(Restrictions.or(Restrictions.eq("age", 23), Restrictions.like("username", "%李%")));
//或者以下写法直接使用SQL语句
criteria.add(Restrictions.sqlRestriction("age=20 or username like '%李%'"));
执行SQL
select this_.USERNAME as USERNAME0_0_, this_.PASSWORD as PASSWORD0_0_, this_.AGE as AGE0_0_ from ROOT.LOGIN this_ where ( this_.AGE=? or this_.USERNAME like ? )
直接使用SQL的执行语句
select this_.USERNAME as USERNAME0_0_, this_.PASSWORD as PASSWORD0_0_, this_.AGE as AGE0_0_ from ROOT.LOGIN this_ where age=20 or username like '%李%'
四、Restrictions常用方法
五、常用方法使用
package demo; import java.util.List; import org.hibernate.Criteria; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; import org.hibernate.criterion.Restrictions; import entity.Login; public class Demo1 { /** * Criteria无查询条件查询所有 */ public static void main(String[] args) { //声明一个集合用来接收结果 List<Login> result=null; //声明SessionFactory SessionFactory factory=null; //声明Session Session session=null; //初始化以上对象 try{ factory=new Configuration().configure().buildSessionFactory(); session=factory.openSession(); //声明Criteria对象传入一个持久化类对象类型 Criteria criteria=session.createCriteria(Login.class); //1.查询用户名为Tom的记录 //criteria.add(Restrictions.eq("username", "Tom")); //2.查询年龄大于等于21同时小于等于25的记录 //criteria.add(Restrictions.ge("age", 21)); //criteria.add(Restrictions.le("age", 25)); //between写法 //criteria.add(Restrictions.between("age", 21, 25)); //3.或者查询年龄=21或者名字中有李的记录 //criteria.add(Restrictions.or(Restrictions.eq("age", 21), Restrictions.like("username", "%李%"))); //sql写法 //criteria.add(Restrictions.sqlRestriction("age=21 or username like '%李%'")); //4.年龄在21,23,25的记录 //criteria.add(Restrictions.in("age", new Integer []{21,23,25})); //5.and用法 criteria.add(Restrictions.and(Restrictions.ge("age", 23), Restrictions.like("username", "%T%"))); //查询使用list方法 result=criteria.list(); }catch(HibernateException e){ e.printStackTrace(); }finally{ session.close(); factory.close(); } System.out.println("=========="); //输出结果 for (Login login : result) { System.out.println("用户名:"+login.getUsername()+" 密码："+login.getPassword()+" 年龄:"+login.getAge()); } } }
六、对结果进行排序
使用Order关键字，进行排序
criteria.addOrder(Order.desc(属性名称));降序
criteria.addOrder(Order.asc（属性名称）);升序
//按年龄降序排序 criteria.addOrder(Order.desc("age")); //按姓名升序排序 criteria.addOrder(Order.asc("username")); //查询使用list方法 result=criteria.list(); //输出结果 for (Login login : result) { System.out.println("用户名:"+login.getUsername()+" 密码："+login.getPassword()+" 年龄:"+login.getAge()); }
七、示例查询
package demo; import java.util.List; import org.hibernate.Criteria; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; import org.hibernate.criterion.Example; import org.hibernate.criterion.Order; import org.hibernate.criterion.Restrictions; import entity.Login; public class Demo2 { /** * Criteria无查询条件查询所有 */ public static void main(String[] args) { //声明一个集合用来接收结果 List<Login> result=null; //声明SessionFactory SessionFactory factory=null; //声明Session Session session=null; //声明一个Login对象，并赋值可以是多个 但不能是主键 Login user=new Login(); user.setAge(21); //初始化以上对象 try{ factory=new Configuration().configure().buildSessionFactory(); session=factory.openSession(); //声明Criteria对象传入一个持久化类对象类型 Criteria criteria=session.createCriteria(Login.class); //加入查询条件 criteria.add(Example.create(user)); //查询使用list方法 result=criteria.list(); }catch(HibernateException e){ e.printStackTrace(); }finally{ session.close(); factory.close(); } System.out.println("=========="); //输出结果 for (Login login : result) { System.out.println("用户名:"+login.getUsername()+" 密码："+login.getPassword()+" 年龄:"+login.getAge()); } } }
八、聚合函数
package demo; import java.util.Iterator; import java.util.List; import org.hibernate.Criteria; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; import org.hibernate.criterion.ProjectionList; import org.hibernate.criterion.Projections; import entity.Login; public class Demo3 { /** * Criteria无查询条件查询所有 */ public static void main(String[] args) { //声明一个集合用来接收结果 List<Login> result=null; //声明SessionFactory SessionFactory factory=null; //声明Session Session session=null; //初始化以上对象 try{ factory=new Configuration().configure().buildSessionFactory(); session=factory.openSession(); //声明Criteria对象传入一个持久化类对象类型 Criteria criteria=session.createCriteria(Login.class); //加入查询条件 //总记录数 //criteria.setProjection(Projections.rowCount()); //平均年龄 //criteria.setProjection(Projections.avg("age")); //分组 criteria.setProjection(Projections.groupProperty("username")); //查询使用list方法 result=criteria.list(); //System.out.println("平均年龄："+result.iterator().next()); //System.out.println("总记录数："+result.iterator().next()); Iterator iterator=result.iterator(); while(iterator.hasNext()){ System.out.println(iterator.next()); } }catch(HibernateException e){ e.printStackTrace(); }finally{ session.close(); factory.close(); } } }
分页
package demo; import java.util.List; import org.hibernate.Criteria; import org.hibernate.HibernateException; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.Configuration; import org.hibernate.criterion.Order; import org.hibernate.criterion.Restrictions; import entity.Login; public class Demo4 { /** * Criteria无查询条件查询所有 */ public static void main(String[] args) { //声明一个集合用来接收结果 List<Login> result=null; //声明SessionFactory SessionFactory factory=null; //声明Session Session session=null; //当前页数第几页 int pageIndex=1; //最大显示记录数 int pageSize=2; //初始化以上对象 try{ factory=new Configuration().configure().buildSessionFactory(); session=factory.openSession(); //声明Criteria对象传入一个持久化类对象类型 Criteria criteria=session.createCriteria(Login.class); //起始记录数 criteria.setFirstResult((pageIndex-1)*pageSize); //每页显示最大记录数 criteria.setMaxResults(pageSize); //查询使用list方法 result=criteria.list(); }catch(HibernateException e){ e.printStackTrace(); }finally{ session.close(); factory.close(); } System.out.println("=========="); //输出结果 for (Login login : result) { System.out.println("用户名:"+login.getUsername()+" 密码："+login.getPassword()+" 年龄:"+login.getAge()); } } }