package cn.bdqn.bean;
/*** * @author 小豆腐*街道对应的实体类**单向的多对一关联*/
public class Street {private Integer id;private String name;//多个街道  属于  一个区县private    District district;  //对应的区县public District getDistrict() {return district;}public void setDistrict(District district) {this.district = district;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Street(Integer id, String name) {super();this.id = id;this.name = name;}public Street() {super();}@Overridepublic String toString() {return "Street [id=" + id + ", name=" + name + "]";}}

<?xml version="1.0"?>
<!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.bdqn.bean"><class name="Street"><id name="id"> <generator class="assigned"/><!-- 手动给主键赋值 --></id>  <property name="name"/><!-- 配置多对一关联name:对应的是  本类中 关联关系的属性名column:对应数据库中 两个表的  外键！class:关联的实体类--><many-to-one name="district" column="districtId" class="District"/> </class>
</hibernate-mapping>

package cn.bdqn.bean;
/*** @author 小豆腐**区县的实体类*/
public class District {private Integer id;private String name;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public District(Integer id, String name) {super();this.id = id;this.name = name;}public District() {super();}@Overridepublic String toString() {return "Street [id=" + id + ", name=" + name + "]";}}

<?xml version="1.0"?>
<!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.bdqn.bean"><class name="District"><id name="id"> <generator class="assigned"/><!-- 手动给主键赋值 --></id>  <property name="name"/></class>
</hibernate-mapping>

        Session session=null;Transaction transaction=null;//获取session  开启事务
        @Beforepublic  void  before(){session=HibernateSessionUtil.getCurrentSession();transaction= session.beginTransaction();}/*** 测试单向的多对一的关联* * 创建对应的区县    新增几个区县   以备后续使用*/@Testpublic   void   testAdd(){District district=new District(3, "区县3");session.save(district);  //保存transaction.commit();  //提交事务
        }//新增 街道的同时 给街道对应的区县赋值
    @Testpublic   void   test01(){//创建一个街道Street street=new Street();street.setId(1);street.setName("街道1");//给对应的区县赋值District district= (District) session.load(District.class, 1);street.setDistrict(district);session.save(street);  //保存transaction.commit();  //提交事务   只会产生一条sql  insert
    }//修改 街道对应的区县
    @Testpublic   void   test02(){//从数据库中获取一个街道Street street=(Street) session.load(Street.class, 1);  // 对应的区县是1District district=(District) session.load(District.class, 2);  // 区县是2//修改street.setDistrict(district);  // 不需要 update  因为两个对象都是持久化对象//提交事务
        transaction.commit();}//删除 街道对应的区县
    @Testpublic   void   test03(){//从数据库中获取一个街道Street street=(Street) session.load(Street.class, 1);  // 对应的区县是2//修改street.setDistrict(null);  //提交事务
        transaction.commit();}

package cn.bdqn.bean;import java.util.ArrayList;
import java.util.List;/*** @author 小豆腐**区县的实体类*  一对多的关联关系*/
public class District {private Integer id;private String name;// 一个区县 有  多个街道private List<Street> streets=new ArrayList<>();public List<Street> getStreets() {return streets;}public void setStreets(List<Street> streets) {this.streets = streets;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public District(Integer id, String name) {super();this.id = id;this.name = name;}public District() {super();}@Overridepublic String toString() {//如果写成streets   会出现 堆栈溢出的异常！return "District [id=" + id + ", name=" + name + ", streets=" + streets.size()+ "]";}}

<?xml version="1.0"?>
<!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.bdqn.bean"><class name="District"><id name="id"> <generator class="assigned"/><!-- 手动给主键赋值 --></id>  <property name="name"/><!-- 设置一对多  name:本类中的关联属性名  集合的名称column: 就是数据库表中的外键order-by="id desc" 按照 街道的id 进行 降序排列inverse：是由谁来维护表与表之间的关系！ 默认是false！（维护）    true（不维护）--><bag name="streets" cascade="all" inverse="true"><key column="districtId"/><one-to-many class="Street"/></bag></class>
</hibernate-mapping>

    /*** 创建几个街道      测试 双向的一对多关联*/@Testpublic   void   test04(){Street street=new Street();street.setId(4);street.setName("街道4");//给对应的区县赋值District district= (District) session.load(District.class, 1);street.setDistrict(district);session.save(street);  //保存//提交事务
        transaction.commit();}//根据区县  获取所管辖的街道
    @Testpublic  void  test05(){District district=(District) session.load(District.class, 1);List<Street> streets = district.getStreets();for (Street street : streets) {System.out.println(street);}}/*** 根据区县  获取所管辖的街道       根据街道的编号 降序排列* 01.只需要在 bag节点中  增加 order-by属性  =  id   desc*/@Testpublic  void  test06(){District district=(District) session.load(District.class, 1);List<Street> streets = district.getStreets();for (Street street : streets) {System.out.println(street);}}/*** 02.使用hql语句*/@Testpublic  void  test07(){String  hql="from  Street s where districtId=:id  order by s.id desc";//创建query对象Query query = session.createQuery(hql);//给参数赋值query.setParameter("id", 1);   //区县编号是1//遍历结果集List<Street> list = query.list();for (Street street : list) {System.out.println(street);}}/*** cascade属性：定义的是关系两端 对象到对象的级联关系！*  必须是  双向的一对多关联！*  *  常用的属性值：*  01.none：默认值！当session操作当前对象的时候，忽略关联的属性！*  02.save-update:当session调用save,saveorUpdate以及update()的时候！*                会级联的保存和修改当前对象以及对象关联的属性！*          001.去区县的xml文件中 的 bag节点 增加 cascade属性！    *          002.直接运行以下代码 *  03.delete: 当session调用 delete（）的时候，会级联删除所关联的对象  ！*  04.all： 包括了save-update和delete！* * 添加区县的同时 添加街道*/@Testpublic  void  test08(){//创建区县District district=new District(4, "区县4");//创建街道Street street1=new Street(5, "街道5");Street street2=new Street(6, "街道6");Street street3=new Street(7, "街道7");//给区县的街道赋值
        district.getStreets().add(street1);district.getStreets().add(street2);district.getStreets().add(street3);//保存区县session.save(district);   //发现 保存了 区县  但是 没有保存对应的街道！
        transaction.commit();/*** 程序执行之后的结果：*  Hibernate: insert into District (name, id) values (?, ?)Hibernate: update Street set districtId=? where id=?Hibernate: update Street set districtId=? where id=?Hibernate: update Street set districtId=? where id=?*//*** 在xml文件中设置了 cascade="save-update" 之后的结果* * 问题：虽然级联保存成功了！*     但是有多余update语句！*     为什么会出现多余的？   两个对象都在维护彼此之间的关系！* *  Hibernate: select street_.id, street_.name as name1_, street_.districtId as districtId1_ from Street street_ where street_.id=?Hibernate: select street_.id, street_.name as name1_, street_.districtId as districtId1_ from Street street_ where street_.id=?Hibernate: select street_.id, street_.name as name1_, street_.districtId as districtId1_ from Street street_ where street_.id=?Hibernate: insert into District (name, id) values (?, ?)Hibernate: insert into Street (name, districtId, id) values (?, ?, ?)Hibernate: insert into Street (name, districtId, id) values (?, ?, ?)Hibernate: insert into Street (name, districtId, id) values (?, ?, ?)Hibernate: update Street set districtId=? where id=?Hibernate: update Street set districtId=? where id=?Hibernate: update Street set districtId=? where id=?*/}/*** cascade="delete"    xml中的配置* 删除 区县 的同时 删除 街道！*/@Testpublic  void  test09(){District  district= (District) session.load(District.class, 1);//获取三个街道Street  street1= (Street) session.load(Street.class, 2);Street  street2= (Street) session.load(Street.class, 3);Street  street3= (Street) session.load(Street.class, 4);session.delete(district);transaction.commit();/***  Hibernate: update Street set districtId=null where districtId=?Hibernate: delete from Street where id=?Hibernate: delete from Street where id=?Hibernate: delete from Street where id=?Hibernate: delete from District where id=?*/}/*** 针对于 多余的sql语句 解决办法！* * 只需要一方来维护表之间的关系！* inverse属性：*   01.默认是false(由我维护！)*   02.inverse=true:这一方不维护关系！（不与数据库交互）*  *   *  不能都维护，也不能都 不维护！ 这个时候关键是谁来维护这个关系？*  双向的一对多！ *  hibernate:规定多的一端来维护关系，那么必须在一的一方设置 inverse=true:*/@Testpublic  void  test10(){//创建区县District district=new District(4, "区县4");//创建街道Street street1=new Street(5, "街道5");Street street2=new Street(6, "街道6");Street street3=new Street(7, "街道7");//给区县的街道赋值
        district.getStreets().add(street1);district.getStreets().add(street2);district.getStreets().add(street3);//保存区县session.save(district);   //发现 保存了 区县  但是 没有保存对应的街道！
        transaction.commit();/*** * 发现  没有了 update语句！* Hibernate: select street_.id, street_.name as name1_, street_.districtId as districtId1_ from Street street_ where street_.id=?Hibernate: select street_.id, street_.name as name1_, street_.districtId as districtId1_ from Street street_ where street_.id=?Hibernate: select street_.id, street_.name as name1_, street_.districtId as districtId1_ from Street street_ where street_.id=?Hibernate: insert into District (name, id) values (?, ?)Hibernate: insert into Street (name, districtId, id) values (?, ?, ?)Hibernate: insert into Street (name, districtId, id) values (?, ?, ?)Hibernate: insert into Street (name, districtId, id) values (?, ?, ?)*/}