HQL查询（示例）
hql查询是操作实体类和属性实现查询。查询语句必须是实体类的方法名。
（1）sql查询是表以及字段，不区分大小写，也叫做结构化的查询语句；
（2）HQL查询的是对象以及对象的属性，区分大小写的。
步骤：
（1）创建Query查询对象，编写hql语句；
（2）调用Query对象里面的方法得到结果。
案例：
卡号实体类：
package com.liuyongqi.MavenHibernateDemo7.entity;
import java.io.Serializable;
/**
* 卡号实体类
* @author Administrator
* @data 2018年8月6日
* @time 上午11:51:34
*/
public class Card implements Serializable {
/**
*
*/
private static final long serialVersionUID = -3229041685479626246L;
private Integer pid; //卡号编号
private String cname; //卡号名称
private Person person; //个人对象
public Card() {
super();
// TODO Auto-generated constructor stub
}
public Card(String cname, Integer pid) {
super();
this.cname = cname;
this.pid = pid;
}
public String getCname() {
return cname;
}
public void setCname(String cname) {
this.cname = cname;
}
public Integer getPid() {
return pid;
}
public void setPid(Integer pid) {
this.pid = pid;
}
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
@Override
public String toString() {
return "Card [pid=" + pid + ", cname=" + cname + ", person=" + person + "]";
}
}
个人实体类：
package com.liuyongqi.MavenHibernateDemo7.entity;
import java.io.Serializable;
/**
* 个人实体类
* @author Administrator
* @data 2018年8月6日
* @time 上午11:49:17
*/
public class Person implements Serializable {
/**
*
*/
private static final long serialVersionUID = -2013313014914594043L;
private Integer pid; //个人编号
private String pname; //个人名称
private Card card; //卡号对象
public Person() {
super();
// TODO Auto-generated constructor stub
}
public Person(String pname) {
super();
this.pname = pname;
}
public Person(Integer pid, String pname) {
super();
this.pid = pid;
this.pname = pname;
}
public Integer getPid() {
return pid;
}
public void setPid(Integer pid) {
this.pid = pid;
}
public String getPname() {
return pname;
}
public void setPname(String pname) {
this.pname = pname;
}
public Card getCard() {
return card;
}
public void setCard(Card card) {
this.card = card;
}
@Override
public String toString() {
return "Person [pid=" + pid + ", pname=" + pname + "]";
}
}
Card.hbm.xml：
person
Person.hbm.xml：
SessionFactoryUtil工具类：
package com.liuyongqi.MavenHibernateDemo7.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
/**
* 提供了开启和关闭session的方法
* @author Administrator
* @data 2018年8月1日
* @time 下午3:32:56
*/
public class SessionFactoryUtil {
//ThreadLocal为每个线程提供一个单独的存储空间
private static ThreadLocal threadLocal=new ThreadLocal();
//私有化静态变量，静态变量只实例化一次
private static SessionFactory sessionFactory;
//实例化一次sessionFactory
static {
Configuration configure = new Configuration().configure();
sessionFactory=configure.buildSessionFactory();
}
//私有化构造方法
private SessionFactoryUtil() {
}
//打开session的方法
public static Session openSession() {
//从ThreadLocal中拿取一个session
Session session = threadLocal.get();
if(null==session) {
//sessionFactory打开一个session
session=sessionFactory.openSession();
//把session又放入ThreadLocal中
threadLocal.set(session);
}
return session;
}
//关闭资源
public static void closeSession() {
//从ThreadLocal中拿取一个session
Session session = threadLocal.get();
if(null==session) {
if(session.isOpen()) {
//关闭session
session.close();
}
threadLocal.set(null);
}
}
public static void main(String[] args) {
Session session = openSession();
System.out.println(session);
System.out.println("ok");
}
}
hql测试类：
(1)查询所有
Session session = SessionFactoryUtil.openSession();
String hql="from Person";
Query query = session.createQuery(hql);
List list = query.list();
for (Person person : list) {
System.out.println(person);
} (2)条件查询
Session session = SessionFactoryUtil.openSession();
String hql = "from Person where pname=?";
Query query = session.createQuery(hql);
query.setParameter(0, "王五");
List list=query.list();
System.out.println(list); 模糊查询：
Session session = SessionFactoryUtil.openSession();
String hql="from Person where pname like'%王%'";
Query query = session.createQuery(hql);
List list=query.list();
System.out.println(list); (3)排序查询：
Session session = SessionFactoryUtil.openSession()
String hql="from Person order by pname desc ";
Query query = session.createQuery(hql);
List list=query.list();
System.out.println(list); (4)分页查询：
Session session = SessionFactoryUtil.openSession();
String hql="from Person";
Query query = session.createQuery(hql);
query.setFirstResult(0);
query.setMaxResults(2);
List list=query.list();
System.out.println(list); (5)投影查询：
Session session = SessionFactoryUtil.openSession();
String hql="select pname from Person";
Query query = session.createQuery(hql);
List list=query.list();
System.out.println(list); (6)聚集查询：
Session session = SessionFactoryUtil.openSession();
String hql="select count(*) from Person";
Query query = session.createQuery(hql);
Object obj = query.uniqueResult();
int count =Integer.parseInt(obj.toString());
System.out.println(count);(7)分组查询：
Session session = SessionFactoryUtil.openSession();
String hql="from Person group by pname having pid>1";
Query query = session.createQuery(hql);
List list=query.list();
System.out.println(list); （8）子查询：
Session session = SessionFactoryUtil.openSession();
String hql="from Card where pid in(from Person where pname like '%王%')";
Query query = session.createQuery(hql);
List list=query.list();
System.out.println(list); （9）多表联查：
Session session = SessionFactoryUtil.openSession();
String hql="from Person p,Card c where p.pid=c.pid";
Query query e= session.createQuery(hql);
List list=qury.list();
for (Object object : list) {
Object[] obj=(Object[]) object;
for (Object object2 : obj) {
System.out.println(object2);
}
System.out.println("------------");
}今天的测试就到这里了，希望大家看完以后自己测试一下
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此文章属于原创，不准随意转载：https://blog.csdn.net/LYQ2332826438