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());
}

}

}