-
什么是关联(association)
1.1 关联指的是类之间的引用关系。如果类A与类B关联，那么被引用的类B将被定义为类A的属性。例如:
public class A{
private B b = new B;
public A(){}
}
1.2 关联的分类：关联可以分为一对一、一对多/多对一、多对多关联
关联是有方向的订单表、订单项表
select * from t_order t,t_orderItem m where t.oid = m.oid
and …class Order{
private STIRNG OID;
…
private Set OrderItems;
}session.get(Order.class,1)
调用此方法
将关联属性自动赋值。
#关键点都在数据库中的外键上面,请好好理解下面这二句SQL和一对多及多对一的关系
#select * from Orders where cid=? //这条SQL返回客户对应的0-n个订单
#select * from Customers where customerId=? //这条SQL返回订单对应的1个客户
#通过这二条SQL不难看出,外键在这里有二个用途:查找客户的订单,查找订单对应的客户
2. 案例:如何建立客户和订单一对多双向关联
2.1 先不建立客户和订单的关联关系,定义实体及映射文件,单独执行保存操作
2.2 建立客户到订单的一对多关联关系
2.3 建立订单到客户的多对一关联关系
<!--1.注释 2.只读-->
<property name="cid" type="java.lang.Integer" column="cid" insert="false" update="false">
</property>
2.4 注意:在Hibernate当中定义实体对象的集合属性时,只能使用接口而不能使用类
#insert属性设置中主控方概念理解:
3. 以客户和订单的一对多双向关联为例,讲解Set元素中的cascade|inverse|outter-join|lazy属性作用
3.1 lazy:默认值为true,true延迟加载,false立即加载(一般设置为true,不使用立即加载,因为影响查询性能)
3.2 outter-join:默认值为false,true使用左外联接查询关联的(但一般不用，因为当我们把该属性设置为true时，所有的查询语句都会默认左外联，那样性能不高)
3.3 inverse:默认值为false,true表示将对方设置为主控方(一对多双向关联中一般将多方设置为主控方,这样可以减少SQL语句的数量,减少多余的操作)
3.4 cascade:用来控制如何操作关联的持久化对象的
3.4.1 none:保存，更新或删除当前对象时，忽略其它关联的对象
3.4.2 save-update:保存、更新时级联保存所有的临时对象，并且级联更新关联的游离对象
3.4.3 delete:通过session的delete方法删除当前对象，级联删除关联的对象
3.4.4 all:等于save-update操作+delete操作
小结：
多方的CRUD与没有建立关联关系之前的操作一致
一方的CRUD与没有建立关联关系之前的操作有变化
D：删除一方之前先删除多方
C：级联操作
R：代码控制多方
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案例:菜单对象的一对多双向自关联
-
如何将多方映射成一个有序的集合
核心
订单表、订单项
级联新增
外键处理的三种方式
1、删除从表对应的实体类中的外键属性
2、在配置的xml中外键属性上添加 insert=false，update=false的设置。
3、在配置的xml中的manyToOne标签中添加insert=false，update=false的设置。
级联新增 casecade=save-update 介绍
级联查询
配置文件介绍以及后台sql的形成过程
级联查询时的问题
Lazy=true介绍 查单个时存在问题
Lazy=false介绍 查所有时存在问题
解决方案：通过字段控制，强制加载。Hibernate.initialize()
普通删除
Order
Add 讲外键的处理
Get/list order.getOrderItems.size讲懒加载的处理，sql形成过程
Del 将关系的处理中的删除
如代码演示：
package com.zking.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
/**
* hibernate工具类
* 未整合框架前使用
* @author Administrator
*
*/
public class HibernateUtli {
private static SessionFactory sessionFactory;
/**
* 存放当前会话
*/
private static ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
/**
* 通过单例管理sessionFactory，整个系统运行过程中只会构建一个sessionFactory对象
*/
static {
//读取配置文件 获取会话 开启事务
sessionFactory = new Configuration().configure().buildSessionFactory();
}
/**
* 建模 获取sessionfactory
* @return
* 2018年10月19日上午10:23:16
*/
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
/**
* 打开一个session
* @return
* 2018年10月19日上午10:20:58
*/
public static Session openSession() {
Session session = threadLocal.get();
if (null == session) {
session = sessionFactory.openSession();
threadLocal.set(session);
}
return session;
}
/**
* 打开与线程绑定的session
* @return
* 2018年10月19日上午10:24:32
*/
public static Session getCurrentSession() {
Session session = threadLocal.get();
if (null == session) {
session = sessionFactory.openSession();// 如果session为空就创建一个session
threadLocal.set(session);// 放到当前的线程中
return session;
}
return session;
}
/**
* 关闭session
*
* 2018年10月19日上午10:21:17
*/
public static void closeSession() {
Session session = threadLocal.get();
if (null != session) {
if (session.isOpen()) {
Transaction transaction = session.beginTransaction();
transaction.commit();
session.close();
}
threadLocal.set(null);
}
}
/**
* 测试
* @param args
* 2018年10月19日上午10:25:41
*/
public static void main(String[] args) {
Session session = openSession();
System.out.println(session.isConnected());
closeSession();
}
}
package com.zking.dao.daoImpl;
import java.util.List;
import org.hibernate.Criteria;
import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.zking.entity.Order;
import com.zking.entity.OrderItem;
import com.zking.util.HibernateUtli;
public class OrderDaoImpl implements IOrderDaoImpl {
@Override
public Integer insertOrder(Order order) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
Integer save = 0;
try {
save = (Integer) session.save(order);
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("新增出现异常");
}
HibernateUtli.closeSession();
return save;
}
@Override
public void deleteOrder(Order order) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
try {
Order o = session.get(Order.class, order.getOrder_id());
System.out.println(o);
for (OrderItem ot : o.getOrderItem()) {
session.delete(ot);
}
session.delete(order);
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("删除出现异常");
}
HibernateUtli.closeSession();
}
@Override
public void editOrder(Order order) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
try {
session.update(order);
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("修改出现异常");
}
HibernateUtli.closeSession();
}
@Override
public Order getOrder(Order order) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
Order t = null;
try {
t = session.get(Order.class, order.getOrder_id());
if (t != null && new Integer(1).equals(order.getInitorderItem())) {
//强制立即加载
Hibernate.initialize(t.getOrderItem());
}
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("查询出现异常");
}
HibernateUtli.closeSession();
return t;
}
@Override
public List<Order> getOrderList(String str) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
List<Order> list = null;
try {
Criteria criteria = session.createCriteria(Order.class);
list = criteria.list();
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("查询出现异常");
}
HibernateUtli.closeSession();
return list;
}
}
package com.zking.dao.daoImpl;
import java.util.List;
import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.zking.entity.OrderItem;
import com.zking.util.HibernateUtli;
public class OrderItemDaoImpl implements IOrderItemDaoImpl {
@Override
public Integer insertOrderItem(OrderItem orderItem) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
Integer save = 0;
try {
save = (Integer) session.save(orderItem);
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("新增出现异常");
}
HibernateUtli.closeSession();
return save;
}
@Override
public void deleteOrderItem(OrderItem orderItem) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
try {
session.delete(orderItem);
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("删除出现异常");
}
HibernateUtli.closeSession();
}
@Override
public void editOrderItem(OrderItem orderItem) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
try {
session.update(orderItem);
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("修改出现异常");
}
HibernateUtli.closeSession();
}
@Override
public OrderItem getOrderItem(OrderItem orderItem) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
OrderItem t = null;
try {
t = session.get(OrderItem.class, orderItem.getOrder_item_id());
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("查询出现异常");
}
HibernateUtli.closeSession();
return t;
}
@Override
public List<OrderItem> getOrderItemList(String str) {
Session session = HibernateUtli.getCurrentSession();
Transaction transaction = session.beginTransaction();
List<OrderItem> list = null;
try {
Criteria criteria = session.createCriteria(OrderItem.class);
list = criteria.list();
transaction.commit();
} catch (Exception e) {
e.printStackTrace();
transaction.rollback();
throw new RuntimeException("查询出现异常");
}
HibernateUtli.closeSession();
return list;
}
}
package com.zking.entity;
import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
public class Order implements Serializable {
/**
* 2018年10月23日下午4:21:50
*/
private static final long serialVersionUID = 1575914611357638677L;
private Integer order_id;
private String order_no;
/**
* 在描述关系的时候，一定用含集合接口进行 一对多关系
*/
private Set<OrderItem> orderItem = new HashSet<>();
private Integer initorderItem = 0; //0 延迟加载 1 立即加载
public Integer getInitorderItem() {
return initorderItem;
}
public void setInitorderItem(Integer initorderItem) {
this.initorderItem = initorderItem;
}
public Set<OrderItem> getOrderItem() {
return orderItem;
}
public void setOrderItem(Set<OrderItem> orderItem) {
this.orderItem = orderItem;
}
@Override
public String toString() {
return "Order [order_id="+ order_id +",order_no="+ order_no +"]";
}
public Integer getOrder_id() {
return order_id;
}
public void setOrder_id(Integer order_id) {
this.order_id = order_id;
}
public String getOrder_no() {
return order_no;
}
public void setOrder_no(String order_no) {
this.order_no = order_no;
}
public Order() {
super();
}
public Order(Integer order_id,String order_no) {
super();
this.order_id = order_id;
this.order_no = order_no;
}
}
package com.zking.entity;
import java.io.Serializable;
public class OrderItem implements Serializable {
/**
* 2018年10月23日下午4:33:58
*/
private static final long serialVersionUID = 2468758266675428160L;
private Integer order_item_id;
private Integer product_id;
private Integer quantity;
private Integer oid;
private Order order;
public Order getOrder() {
return order;
}
public void setOrder(Order order) {
this.order = order;
}
@Override
public String toString() {
return "OrderItem [order_item_id="+ order_item_id +",product_id="+ product_id +",quantity="+ quantity +",oid="+ oid +"]";
}
public Integer getOrder_item_id() {
return order_item_id;
}
public void setOrder_item_id(Integer order_item_id) {
this.order_item_id = order_item_id;
}
public Integer getProduct_id() {
return product_id;
}
public void setProduct_id(Integer product_id) {
this.product_id = product_id;
}
public Integer getQuantity() {
return quantity;
}
public void setQuantity(Integer quantity) {
this.quantity = quantity;
}
public Integer getOid() {
return oid;
}
public void setOid(Integer oid) {
this.oid = oid;
}
public OrderItem() {
super();
}
public OrderItem(Integer order_item_id,Integer product_id,Integer quantity,Integer oid) {
super();
this.order_item_id = order_item_id;
this.product_id = product_id;
this.quantity = quantity;
this.oid = oid;
}
}
<?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>
<!--
级联查询原理：
session.get(Order.class, 2);
select * from t_hibernate_order where order_id = ?(2)
2 P2 模拟查出来的数据
Order o = lass.forName("com.zking.entity.Order").newInstance(); 反射实例化
o.setorder_id(2).... 反射赋值
通过one-to-many中的class属性找到对应的映射文件
select * from t_hibernate_order_item where oid = ?(2)
查出来的数据
ResultSet rs
com.zking.entity.Order
原理是mvc EntityBaseDao，最后获取到有值得list集合 -> orderItem
o.setOrderItem(orderItem)
-->
<class name="com.zking.entity.Order" table="t_hibernate_order">
<id name="order_id" type="java.lang.Integer" column="order_id">
<generator class="increment" />
</id>
<property name="order_no" type="java.lang.String" column="order_no"></property>
<!--
cascade:配置级联关系
inverse:反方，是否将关联关系交给对方控制
lazy="false":立即加载，默认延迟加载
-->
<set name="orderItem" cascade="save-update" inverse="false" >
<!-- 配置外键字段 -->
<key column="oid"></key>
<!-- 配置外键关联的类（表） -->
<one-to-many class="com.zking.entity.OrderItem"/>
</set>
</class>
</hibernate-mapping>
<?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>
<class name="com.zking.entity.OrderItem" table="t_hibernate_order_item">
<id name="order_item_id" type="java.lang.Integer" column="order_item_id">
<generator class="increment" />
</id>
<property name="product_id" type="java.lang.Integer" column="product_id"></property>
<property name="quantity" type="java.lang.Integer" column="quantity"></property>
<property name="oid" type="java.lang.Integer" column="oid" insert="false" update="false"></property>
<!-- 会报错 -->
<many-to-one name="order" class="com.zking.entity.Order" column="oid"></many-to-one>
</class>
</hibernate-mapping>
package com.zking.test;
import java.util.List;
import org.junit.Before;
import org.junit.Test;
import com.zking.dao.daoImpl.OrderDaoImpl;
import com.zking.entity.Order;
import com.zking.entity.OrderItem;
public class OrderDAOTest {
private OrderDaoImpl orderDao = null;
private Order order = null;
@Before
public void setUp() throws Exception {
orderDao = new OrderDaoImpl();
order = new Order();
}
/**
* 提交含有六个订单项的一个订单
*
* 2018年10月23日下午7:32:48
*/
@Test
public void testOrderAdd() {
OrderItem orderItem = null;
order.setOrder_no("P2");
for (int i = 1; i < 7; i++) {
orderItem = new OrderItem();
orderItem.setProduct_id(i);
orderItem.setQuantity(i);
order.getOrderItem().add(orderItem);
orderItem.setOrder(order);
}
this.orderDao.insertOrder(order);
}
@Test
public void testDel() {
order.setOrder_id(2);
/**
* 联表删除解决方案：
* 1.cascade="all" 设置为all,不推荐直接填写delete
* 2.在dao层的删除方法中先循环删除所有外键，再删主键
*/
this.orderDao.deleteOrder(order);
}
@Test
public void testget() {
order.setOrder_id(2);
order.setInitorderItem(1);
order = this.orderDao.getOrder(order);
System.out.println(order);
/**
* Lazy=true介绍 查单个时存在问题 ：当要真正用到查询对象时候，session已经关闭
* 不存在初始化代理
* could not initialize proxy(代理) - no Session
* 懒加载（延迟加载）问题：
* 将查询的oid(object id)保存到session的代理proxy中当要真正用到查询对象时候，再去执行SQL
* 解决问题：
* 强制立即加载：lazy="false":立即加载，默认延迟加载
*/
System.out.println(order.getOrderItem().size());
}
@Test
public void testgetList() {
List<Order> orderList = this.orderDao.getOrderList("");
/**
*Lazy=false介绍 查所有时存在问题 : 性能低
*/
for (Order order : orderList) {
System.out.println(order);
System.out.println(order.getOrderItem().size());
}
}
}
package com.zking.test;
import org.junit.Before;
import org.junit.Test;
import com.zking.dao.daoImpl.OrderItemDaoImpl;
import com.zking.entity.Order;
import com.zking.entity.OrderItem;
public class OrderItemDAOTest {
private OrderItemDaoImpl orderItemDao = null;
private Order order = null;
@Before
public void setUp() throws Exception {
orderItemDao = new OrderItemDaoImpl();
order = new Order();
}
@Test
public void testOrderItemAdd() {
OrderItem orderItem = new OrderItem();
order.setOrder_id(1);
orderItem.setOrder(order);
orderItem.setProduct_id(12);
orderItem.setQuantity(55);
// Repeated column in mapping for entity: com.zking.entity.OrderItem column: oid (should be mapped with insert="false" update="false")
// 实体映射中的重复列:com.zking.entity。OrderItem列:oid(应该用insert="false" update="false"进行映射)
this.orderItemDao.insertOrderItem(orderItem);
}
}