hibernate框架学习之数据查询（QBC）helloworld

Posted 2020-12-24 架构师小跟班

package cn.itcast.h3.query.hql;

import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.criterion.DetachedCriteria;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Projection;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Property;
import org.hibernate.criterion.Restrictions;

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

//Criteria查询(QBC)
public class CriteriaApp {
    // 简单查询
    void testSimpleCriteria() {
        Session s = HibernateUtil.getSession();
        Criteria c = s.createCriteria(TeacherModel.class);
        List<TeacherModel> queryList = c.list();
        for (TeacherModel tm : queryList) {
            System.out.println(tm);
        }
        s.close();
    }

    // 查询排序
    void testCriteriaOrder() {
        Session s = HibernateUtil.getSession();
        Criteria c = s.createCriteria(StudentModel.class);
        c.addOrder(Order.asc("age"));
        c.addOrder(Order.desc("studentName"));
        List<StudentModel> queryList = c.list();
        for (StudentModel tm : queryList) {
            System.out.println(tm);
        }
        s.close();
    }

    // 按条件查询
    void testCriteriaCondition() {
        Session s = HibernateUtil.getSession();
        Criteria c = s.createCriteria(StudentModel.class);
        // 从上向下，全部默认为并且关系
        // c.add(Restrictions.like("studentName", "%虎%"));
        // c.add(Restrictions.gt("age", 22));
        // 使用关系描述条件
        // c.add(Restrictions.or(Restrictions.like("studentName", "%虎%"),
        // Restrictions.lt("age", 22)));
        // c.add(
        // Restrictions.and(
        // Restrictions.eq("aa", 123),
        // Restrictions.and(
        // Restrictions.lt("aa", 232),
        // Restrictions.eq("", 123)
        // )
        // )
        // );

        List<StudentModel> queryList = c.list();
        for (StudentModel tm : queryList) {
            System.out.println(tm);
        }
        s.close();
    }

    // 链式风格
    void testCriteriaLink() {
        Session s = HibernateUtil.getSession();
        Criteria c = s.createCriteria(StudentModel.class);
        c.add(Restrictions.like("studentName", "%虎%")).add(    Restrictions.gt("age", 22));
        List<StudentModel> queryList = c.list();
        for (StudentModel tm : queryList) {
            System.out.println(tm);
        }
        s.close();
    }
    // 投影风格
    void testCriteriaShadow() {
        Session s = HibernateUtil.getSession();
        Criteria c = s.createCriteria(StudentModel.class);
//        投影单个字段
//        c.setProjection(Property.forName("age"));
//        List<Integer> queryList = c.list();
//        for (Integer age : queryList) {
//            System.out.println(age);
//        }
//        投影多个字段
        c.setProjection(
            Projections.projectionList()
                .add(Property.forName("studentName"))
                .add(Property.forName("age"))
            );
        List<Object[]> queryList =c.list();
        for(Object[] objs:queryList){
            for(Object obj:objs){
                System.out.println(obj);
            }
            System.out.println("----------------");
        }
        s.close();
    }
    //多表关联查询
    void testMulQuery(){
        Session s = HibernateUtil.getSession();
        Criteria c = s.createCriteria(StudentModel.class);
        c.createAlias("teacher", "t");
        c.add(Restrictions.eq("t.teacherName", "李若亮"));
        List<StudentModel> queryList = c.list();
        for (StudentModel tm : queryList) {
            System.out.println(tm);
        }
        s.close();
    }
    //离线查询DetachedCriteria
    void testDetachedCriteria(){
        DetachedCriteria dc = DetachedCriteria.forClass(StudentModel.class);
        dc.createAlias("teacher", "t");
        dc.add(Restrictions.eq("t.teacherName", "雅典娜"));
        //..一路传递到数据层
        
        Session s = HibernateUtil.getSession();
        Criteria c = dc.getExecutableCriteria(s);
        List<StudentModel> queryList = c.list();
        for (StudentModel tm : queryList) {
            System.out.println(tm);
        }
        s.close();
    }
    
    public static void main(String[] args) {
        new CriteriaApp().testDetachedCriteria();
    }
}