hibernate_4

hibernate_day04

02-查询总结&HQL基础语法详解_

hibernate的检索方式：导航对象图检索方式、OID检索方式、HQL检索方式、QBC检索方式、SQL检索方式

导航对象图检索方式

导航对象图检索方式是根据已经加载的对象，导航到它关联的对象。利用类与类之间的关系来检索。譬如要查找一个联系人对应的客户，就可以由联系人对象自动导航找到联系人所属的客户对象：

@Test public void test1() { Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- LinkMan linkMan = session.get(LinkMan.class, 5l); Customer customer = linkMan.getCustomer(); System.out.println(customer.getCust_name()); //---------------------------------------------------- tx.commit(); session.close(); }

OID检索方式

OID检索方式主要利用session对象的get()和load（）方法加载某条记录对应的对象，有下面两种方式：

@Test public void test2() { Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- //LinkMan linkMan = session.get(LinkMan.class, 5l); LinkMan linkMan = session.load(LinkMan.class, 5l); System.out.println(linkMan.getLkm_name()); //---------------------------------------------------- tx.commit(); session.close(); }

HQL检索

HQL检索方式基本了解

hibernate query language是面向对象的检索语言，使用的是类、对象、属性的概念，而没有表和字段的概念，具有如下功能： 在查询语句中设定各种查询条件 支持投影查询，即仅检索初对象的部分属性 支持分页查询 支持分组查询，允许使用group by,having关键字 提供内置聚集函数，如sum() min() max() 能够调用用户自定SQL函数。 支持子查询，即嵌套查询 支持动态参数绑定

基本用法：

//基本语法 @Test public void fun1(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from  cn.itcast.domain.Customer ";//完整写法 String hql2 = " from  Customer "; //简单写法 //String hql3 = " from java.lang.Object "; Query query = session.createQuery(hql); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //排序 public void fun2(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " from  cn.itcast.domain.Customer order by cust_id asc ";//完整写法 String hql2 = " from  cn.itcast.domain.Customer order by cust_id desc ";//完整写法 Query query = session.createQuery(hql2); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); }   @Test //条件查询 public void fun3(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " from  cn.itcast.domain.Customer where cust_id =? ";//完整写法 String hql2 = " from  cn.itcast.domain.Customer where cust_id = :id ";//完整写法 Query query = session.createQuery(hql2); //query.setParameter(0, 2l); query.setParameter("id", 2l); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //分页查询 public void fun4(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " from  cn.itcast.domain.Customer  ";//完整写法 Query query = session.createQuery(hql1); //limit ?,? // (当前页数-1)*每页条数 query.setFirstResult(2); query.setMaxResults(2); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //统计查询 //count计数 //sum 求和 //avg平均数 //max //min public void fun5(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " select count(*) from  cn.itcast.domain.Customer  ";//完整写法 String hql2 = " select sum(cust_id) from  cn.itcast.domain.Customer  ";//完整写法 String hql3 = " select avg(cust_id) from  cn.itcast.domain.Customer  ";//完整写法 String hql4 = " select max(cust_id) from  cn.itcast.domain.Customer  ";//完整写法 String hql5 = " select min(cust_id) from  cn.itcast.domain.Customer  ";//完整写法 Query query = session.createQuery(hql5); Number number  = (Number) query.uniqueResult(); System.out.println(number); //---------------------------------------------------- tx.commit(); session.close(); } @Test //投影查询 public void fun6(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql1 = " select cust_name from  cn.itcast.domain.Customer  "; String hql2 = " select cust_name,cust_id from  cn.itcast.domain.Customer  "; String hql3 = " select new Customer(cust_id,cust_name) from  cn.itcast.domain.Customer  "; Query query = session.createQuery(hql3); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); }

03-HQL多表语法详解_

package cn.itcast.a_hql;   import java.util.Arrays; import java.util.List;   import org.hibernate.Query; import org.hibernate.Session; import org.hibernate.Transaction; import org.junit.Test;   import cn.itcast.domain.Customer; import cn.itcast.utils.HibernateUtils;   //学习HQL语法(不常用) -多表查询语法 public class Demo2 { //回顾-原生SQL // 交叉连接-笛卡尔积(避免) // select * from A,B // 内连接 // |-隐式内连接 // select * from A,B  where b.aid = a.id // |-显式内连接 // select * from A inner join B on b.aid = a.id // 外连接 // |- 左外 // select * from A left [outer] join B on b.aid = a.id // |- 右外 // select * from A right [outer] join B on b.aid = a.id //--------------------------------------------------------------------- //HQL的多表查询 //内连接(迫切) //外连接 // |-左外(迫切) // |-右外(迫切) @Test //HQL 内连接 =>将连接的两端对象分别返回.放到数组中. public void fun1(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from Customer c inner join c.linkMens "; Query query = session.createQuery(hql); List list = query.list(); for(Object[] arr : list){ System.out.println(Arrays.toString(arr)); } //---------------------------------------------------- tx.commit(); session.close(); } @Test //HQL 迫切内连接 =>帮我们进行封装.返回值就是一个对象 public void fun2(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from Customer c inner join fetch c.linkMens "; Query query = session.createQuery(hql); List list = query.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //HQL 左外连接 =>将连接的两端对象分别返回.放到数组中. public void fun3(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from Customer c left join c.linkMens "; Query query = session.createQuery(hql); List list = query.list(); for(Object[] arr : list){ System.out.println(Arrays.toString(arr)); } //---------------------------------------------------- tx.commit(); session.close(); } @Test //HQL 右外连接 =>将连接的两端对象分别返回.放到数组中. public void fun4(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- String hql = " from Customer c right join c.linkMens "; Query query = session.createQuery(hql); List list = query.list(); for(Object[] arr : list){ System.out.println(Arrays.toString(arr)); } //---------------------------------------------------- tx.commit(); session.close(); } }

04-Criteria语法介绍_

基本查询

package cn.itcast.b_criteria;   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 cn.itcast.domain.Customer; import cn.itcast.utils.HibernateUtils;   //学习Criteria语法 public class Demo { @Test //基本语法 public void fun1(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- Criteria c = session.createCriteria(Customer.class); List list = c.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //条件语法 public void fun2(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- Criteria c = session.createCriteria(Customer.class); // c.add(Restrictions.idEq(2l)); c.add(Restrictions.eq("cust_id",3l)); List list = c.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //分页语法 -与HQL一样 public void fun3(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- Criteria c = session.createCriteria(Customer.class); //limit ?,? c.setFirstResult(0); c.setMaxResults(2); List list = c.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //排序语法 public void fun4(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- Criteria c = session.createCriteria(Customer.class); //c.addOrder(Order.asc("cust_id")); c.addOrder(Order.desc("cust_id")); List list = c.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } @Test //统计语法 public void fun5(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- Criteria c = session.createCriteria(Customer.class); //设置查询目标 c.setProjection(Projections.rowCount()); List list = c.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } }

05-离线查询对象_

package cn.itcast.b_criteria;   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.Order; import org.hibernate.criterion.Projections; import org.hibernate.criterion.Restrictions; import org.junit.Test;   import cn.itcast.domain.Customer; import cn.itcast.utils.HibernateUtils;   //学习离线Criteria public class Demo2 { @Test public void fun1(){ //Service/web层 DetachedCriteria dc  = DetachedCriteria.forClass(Customer.class); dc.add(Restrictions.idEq(3l));//拼装条件(全部与普通Criteria一致) //---------------------------------------------------- Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- Criteria c = dc.getExecutableCriteria(session); List list = c.list(); System.out.println(list); //---------------------------------------------------- tx.commit(); session.close(); } }

06-类级别加载策略_

package cn.itcast.c_lazy;   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 cn.itcast.domain.Customer; import cn.itcast.utils.HibernateUtils;   //懒加载|延迟加载 public class Demo { @Test // get方法 :调用立即查询。没有加载策略。立即加载.执行方法时立即发送sql语句查询结果 public void fun1(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- Customer c = session.get(Customer.class, 2l); System.out.println(c); //---------------------------------------------------- tx.commit(); session.close(); } @Test // load方法(默认):是在执行时,不发送任何sql语句.返回一个对象.使用该对象时,才执行查询. // 延迟加载:仅仅获得没有使用.不会查询.在使用时才进行查询. // 是否对类进行延迟加载:可以通过在class元素上配置lazy属性来控制. //lazy:true  加载时,不查询.使用时才查询b，查询类时会返回代理对象，会在使用属性时，根据关联的session查询数据库，加载数据。 //lazy:false 调用加载时立即查询.使用懒加载确保属性加载数据时，session还是打开的。 public void fun2(){ Session session = HibernateUtils.openSession(); Transaction tx = session.beginTransaction(); //---------------------------------------------------- Customer c = session.load(Customer.class, 3l); System.out.println(c); //---------------------------------------------------- tx.commit(); session.close(); } } 为了提高效率，建议使用延迟加载（懒加载）

07-关联级别策略介绍_ Customer.hbm.xml

xml version="1.0" encoding="UTF-8"?> DOCTYPE hibernate-mapping PUBLIC      "-//Hibernate/Hibernate Mapping DTD 3.0//EN"     "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="cn.itcast.domain" > <class name="Customer" table="cst_customer" lazy="true" > <id name="cust_id"  > <generator class="native">generator> id> <property name="cust_name" column="cust_name" >property> <property name="cust_source" column="cust_source" >property> <property name="cust_industry" column="cust_industry" >property> <property name="cust_level" column="cust_level" >property> <property name="cust_linkman" column="cust_linkman" >property> <property name="cust_phone" column="cust_phone" >property> <property name="cust_mobile" column="cust_mobile" >property>     <set name="linkMens" batch-size="3"  > <key column="lkm_cust_id" >key> <one-to-many class="LinkMan" /> set> class> hibernate-mapping>