hibernate笔记4--qbc查询

Criteria:是一种完全面向对象的查询方式，Criteria查询也叫做qbc查询（query by Criteria）。
         查询全部，分页查询，统计查询，条件查询，排序查询，离线查询
代码演示:
     1.建库;
     2.导入jar包(required/log4j/mysqlconnector)
     2.建实体类(注意持久化类的编写规则);
     3.编制映射关系文件(Linkman.hbm.xml);
     4.编制核心配置文件(hibernate.cfg.xml);
     5.编写工具类(HibernateUtils.java),增加getCurrentSession方法;
     6.编写测试代码;
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6.编写测试代码;

package demo;

import java.util.List;

import org.hibernate.Criteria;
 import org.hibernate.Session;
 import org.hibernate.Transaction;
 import org.hibernate.criterion.Order;
 import org.hibernate.criterion.Projections;
 import org.hibernate.criterion.Restrictions;
 import org.junit.Test;

import entity.Linkman;
 import utils.HibernateUtils;

//QBC查询
public class Demo03 {
     // 查询所有
    @Test
     public void findAll() {
         // 获取当前线程session
         Session cs = HibernateUtils.getCurrentSession();
         // 开启事务并返回事务对象
        Transaction tx = cs.beginTransaction();
         // 获取criteria对象,同时即进行查询所有
        Criteria cc = cs.createCriteria(Linkman.class);
         // 获取结果集
        List list = cc.list();
         for (Object object : list) {
             System.out.println(object);
         }
         // 提交事务
        tx.commit();
     }

    // 条件查询
    @Test
     public void findCondition() {
         // 获取当前线程session
         Session cs = HibernateUtils.getCurrentSession();
         // 开启事务,并返回事务对象
        Transaction tx = cs.beginTransaction();
         // 获取criteria
         Criteria c = cs.createCriteria(Linkman.class);
         c.add(Restrictions.like("lkmName", "R%"));
         // 获取结果集
        List list = c.list();
         for (Object object : list) {
             System.out.println(object);
         }
         // 提交事务
        tx.commit();
     }

    // 分页查询
    @Test
     public void findByPage() {
         // 获取当前 线程session
         Session cs = HibernateUtils.getCurrentSession();
         // 开启事务,并返回事务对象
        Transaction tx = cs.beginTransaction();
         // 获取criteria
         Criteria c = cs.createCriteria(Linkman.class);
         // 调用方法,分页查询
        c.setFirstResult(0);
         c.setMaxResults(1);
         // 获取结果集
        List list = c.list();
         for (Object object : list) {
             System.out.println(object);
         }
         // 提交事务
        tx.commit();
     }

    // 排序查询
    @Test
     public void findWithOrder() {
         // 获取当前线程session
         Session cs = HibernateUtils.getCurrentSession();
         // 开启事务,并返回事务对象
        Transaction tx = cs.beginTransaction();
         // 获取criteria
         Criteria c = cs.createCriteria(Linkman.class);
         // 调用方法,倒序查询
        c.addOrder(Order.desc("lkmId"));
         // 获取结果集
        List list = c.list();
         for (Object object : list) {
             System.out.println(object);
         }
         // 提交事务
        tx.commit();
     }

    // 统计查询
    @Test
     public void findCount() {
         // 获取当前线程session
         Session cs = HibernateUtils.getCurrentSession();
         // 开启事务,并返回事务对象
        Transaction tx = cs.beginTransaction();
         // 获取criteria
         Criteria c = cs.createCriteria(Linkman.class);
         // 调用方法,统计查询
        c.setProjection(Projections.count("lkmId"));
         // 获取结果
        Object obj = c.uniqueResult();
         System.out.println(obj);
         // 提交事务
        tx.commit();
     }
 }
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离线查询:模拟三层架构
package demo;

import java.util.List;

import org.hibernate.Criteria;
 import org.hibernate.Session;
 import org.hibernate.Transaction;
 import org.hibernate.criterion.DetachedCriteria;
 import org.hibernate.criterion.Restrictions;
 import org.junit.Test;

import entity.Linkman;
 import utils.HibernateUtils;

//离线查询
public class Demo04 {
     @Test
     public void web() {
         DetachedCriteria dc = DetachedCriteria.forClass(Linkman.class);
         dc.add(Restrictions.eq("lkmId", 4L));
         service(dc);
     }

    public void service(DetachedCriteria dc) {
         dao(dc);
     }

    public void dao(DetachedCriteria dc) {
         Session cs = HibernateUtils.getCurrentSession();
         Transaction tx = cs.beginTransaction();
         Criteria c = dc.getExecutableCriteria(cs);
         List list = c.list();
         for (Object object : list) {
             System.out.println(object);
         }
         tx.commit();

    }
 }