hibernate框架学习之数据查询（HQL）helloworld

Posted 2020-12-24 架构师小跟班

package cn.itcast.h3.hql;

import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;

import cn.itcast.h3.hql.vo.StudentModel;
import cn.itcast.h3.hql.vo.TeacherModel;
import cn.itcast.h3.util.HibernateUtil;

public class HQLApp {
    //测试简单查询
    void testSimple(){
        Session s = HibernateUtil.getSession();
        
        //1.HQL
        String hql = "from TeacherModel";
        //2.Query
        Query q = s.createQuery(hql);
        //3.获取查询结果
        List<TeacherModel> queryList = q.list();
        for(TeacherModel tm:queryList){
            System.out.println(tm);
        }
        
        s.close();
    }
    //链式格式
    void testLinked(){
        Session s = HibernateUtil.getSession();
        
        //3.获取查询结果
        List<TeacherModel> queryList = s.createQuery( "from TeacherModel where uuid <=:uuid").setFirstResult(1).setMaxResults(3).setLong("uuid", 3L).list();
        
        for(TeacherModel tm:queryList){
            System.out.println(tm);
        }
        
        s.close();
    }
    //别名格式
    void testAlias(){
        Session s = HibernateUtil.getSession();
        
        //1.HQL
        String hql = "select um.nick from TeacherModel um";
        //2.Query
        Query q = s.createQuery(hql);
        //3.获取查询结果
        List<String> queryList = q.list();
        for(String tm:queryList){
            System.out.println(tm);
        }
        
        s.close();
    }
    //聚合函数
    void testFunctoin(){
        Session s = HibernateUtil.getSession();
        //1.HQL
        String hql = "select sum(age) from StudentModel";
        //2.Query
        Query q = s.createQuery(hql);
        Long avgAge = (Long) q.uniqueResult();
        System.out.println(avgAge);
        s.close();
    }
    //按条件查询
    void testEntityQuery(){
        Session s = HibernateUtil.getSession();
        //1.HQL
        //编号为4的老师有哪些学生
//        String hql = "from StudentModel where  teacher.uuid= :uuid";
//        //2.Query
//        Query q = s.createQuery(hql);
//        q.setLong("uuid",4L);
        
        String hql = "from StudentModel where teacher = :teacher";
        Query q = s.createQuery(hql);
        TeacherModel tm = new TeacherModel();
        tm.setUuid(4L);
//        tm.setTeacherName("李若亮");
        //为hql赋值对象参数
        q.setEntity("teacher", tm);
        List<StudentModel> queryList = q.list();
        for(StudentModel sm:queryList){
            System.out.println(sm);
        }
    }
    //无条件查询
    void testNoCondQuery(){
        Session s = HibernateUtil.getSession();
        
        String hql = "from TeacherModel where teacherName = nick";
        Query q = s.createQuery(hql);
        List<TeacherModel> queryList = q.list();
        for(TeacherModel sm:queryList){
            System.out.println(sm);
        }
    }
    //投影查询
    void testOtherQuery(){
        Session s = HibernateUtil.getSession();
        
        String hql = "select new TeacherModel(teacherName,nick) from TeacherModel";
        Query q = s.createQuery(hql);
        List<TeacherModel> queryList = q.list();
        for(TeacherModel sm:queryList){
            System.out.println(sm);
        }
    }
    //投影查询list
    void testOtherQuery2(){
        Session s = HibernateUtil.getSession();
        
        String hql = "select new list(teacherName,nick) from TeacherModel";
        Query q = s.createQuery(hql);
        List<List<String>> queryList = q.list();
        for(List<String> sm:queryList){
            for(String sa:sm){
                System.out.println(sa);
            }
        }
    }
    //查询分组
    void testGroupQuery(){
        Session s = HibernateUtil.getSession();
        
        String hql = "select skill,count(skill) from StudentModel group by skill";
        Query q = s.createQuery(hql);
        List<Object[]> queryList = q.list();
        for(Object[] objs:queryList){
            for(Object obj:objs){
                System.out.print(obj+"	");
            }
            System.out.println();
        }
    }
    //查询分组
    void testObejcts(){
        Session s = HibernateUtil.getSession();
        
        String hql = "from java.lang.Object";
        Query q = s.createQuery(hql);
        List<Object> queryList = q.list();
        for(Object obj:queryList){
            System.out.println(obj);
        }
    }
    //配置格式的查询
    void testConfQuery(){
        Session s = HibernateUtil.getSession();
        
        Query q = s.getNamedQuery("getAll");
        q.setString("name", "李若亮");
        List<Object> queryList = q.list();
        for(Object obj:queryList){
            System.out.println(obj);
        }
    }
    
    public static void main(String[] args) {
        new HQLApp().testConfQuery();
    }
}