Hibernate=====HQL实用技术-白红宇

Hibernate=====HQL实用技术

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发布时间：2019-06-14

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Hibernate支持三种查询语言：HQL查询、Criteria查询和原生SQL查询

HQL(hibernate Query Language，hibernate查询语言)是一种面向对象查询语言，其中没有表和字段的概念，只有类、对象和属性的概念

语法：

　　form子句：form +全类名 / form + 类名（查询所有）

　　select子句：select dept.deptname from Dept

　　where子句：from dept where deptName='sales';

HQL执行语句

　　　例子：form子句、select子句、where子句以及参数查询

　　　　建立实体类

public class Dept {    private Integer deptno;    private String dname;    public Dept() {    }    public Dept(Integer deptno, String dname) {        this.deptno = deptno;        this.dname = dname;    }    public Integer getDeptno() {        return deptno;    }    public void setDeptno(Integer deptno) {        this.deptno = deptno;    }    public String getDname() {        return dname;    }    public void setDname(String dname) {        this.dname = dname;    }}

测试方法

package cn;import cn.happy.entity.Dog;import cn.hib.entity.Dept;import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import org.junit.Before;import org.junit.Test;import java.util.List;/** * Created by a on 2017/8/20. */public class Test924 {    Configuration cfg;    SessionFactory factory;    Session session;    Transaction tx;    @Before    public void beforeTest(){        //创建配置对象        cfg=new Configuration().configure();        //根据配置对象创建SessonFactory        factory=cfg.buildSessionFactory();        //根据SessionFactory创建Session        session=factory.getCurrentSession();        //session=factory.openSession();        //开启事务        tx=session.beginTransaction();    }    @Test    public void testlist(){        String hql="from Dept";        Query query=session.createQuery(hql);        List
     
       list=query.list();        for (Dept dept : list){            System.out.println(dept.getDname());        }    }    @Test    public void selectSomeColumnFromTable(){        String hql="select dept.deptno,dept.dname from Dept";        Query query=session.createQuery(hql);        List
      
       list=query.list();        for(Object[] obj : list){            for (Object child : obj){                System.out.println(child);            }        }    }    @Test    public void selectSomesColumnFromTable(){        String hql="select new Dept(dept.deptno,dept.dname) from Dept dept";        Query query=session.createQuery(hql);        List
       
         list=query.list();        for (Dept dept : list){            System.out.println(dept.getDname());        }    }    @Test    public void selectSomeRecordsFromTable(){        String hql="from dept.deptno,dept.dname from Dept dept where dept.dname='RESEARCH'";        Query query=session.createQuery(hql);        List
        
          list=query.list();        for (Dept dept : list){            System.out.println(dept.getDname());        }    }    //案例：参数查询： 方案一：匿名占位符“?”    @Test    public void selectByConditionNiming(){        String hql="from Dept dept where dname=?";        Query query=session.createQuery(hql);        query.setParameter(0,"RESEARCH");        List
         
           list=query.list();        for(Dept dept : list){            System.out.println(dept.getDname());        }    }    //案例：参数查询：方案二：    @Test    public void selectByConditionParametername(){        String hql="from Dept dept where dname=:dname";        Query query=session.createQuery(hql);        query.setParameter("dname","RESEARCH");        List
          
            list=query.list(); for(Dept dept : list){ System.out.println(dept.getDname()); } } //案例：参数查询：方案三：name 参数名称绑定++++对象属性 @Test public void selectByConditionParameternameAndObjectAttribute(){ String hql="from Dept dept where dname=:dname"; Dept dd=new Dept(); dd.setDname("RESEARCH"); Query query=session.createQuery(hql); query.setProperties(dd); List
           
             list=query.list(); for(Dept dept : list){ System.out.println(dept.getDname()); } }}