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01-03-03【Nhibernate (版本3.3.1.4000) 出入江湖】cascade的测试

相关文章:

http://www.cnblogs.com/amboyna/archive/2008/02/18/1072260.html
注意上面是hibernate,不是Nhibernate,这解释是否用于Nhibernate,自己验证。

cascade的取值范围:
all : 所有情况下均进行关联操作。 
none:所有情况下均不进行关联操作。这是默认值。 
save-update:在执行save/update/saveOrUpdate时进行关联操作。 
delete:在执行delete时进行关联操作。

all的意思是save-update + delete 
all-delete-orphan 的意思是当对象图中产生孤儿节点时,在数据库中删除该节点 
all比较好理解,举个例子说一下all-delete-orphan: 
Category与Item是一对多的关系,也就是说Category类中有个Set类型的变量items. 
举个例子,现items中存两个Item, item1,item2,如果定义关系为all-delete-orphan 
当items中删除掉一个item(比如用remove()方法删除item1),那么被删除的Item类实例 
将变成孤儿节点,当执行category.update(),或session.flush()时 
hibernate同步缓存和数据库,会把数据库中item1对应的记录删掉




说在前头:
关于是否要级联操作,In my Opinion,还要看实际情况,
1.看关系是否属于识别性(如:鸟与翅膀的关系)与非识别性(独立个体:老师与学生的关系),
2.看业务需求。
3.看你老大的。。你懂的

-----------------------------------一言归正传:

Customer和Order的关系是1对多,即是:1个Customer有多个Order

测试一:cascade="all"

Customer.hbm.xml:
  <class name="Model.Customer, Model"
         discriminator-value="0">
。。。。
    <set name="Orders" table="Order" generic="true"
          inverse="true" cascade="all">
      <key column="CustomerId" foreign-key="FK_CustomerOrders"/>
      <one-to-many class="Model.Order,Model"/>
    </set>
  </class>
</hibernate-mapping>

 测试代码清单一:

 1         /// <summary>
 2         /// 测试联级删除
 3         /// Customer和Order配置了cascade="all",
 4         /// 但是先在内存中解除从属关系,使之成为orphan (孤儿)
 5         /// </summary>
 6         [TestMethod]
 7         public void TestDeleteCustomer_Cascade_All_RemoveOrderInMemery()
 8         {
 9             CustomerService customerService = new CustomerService();
10             OrderService orderService = new OrderService();
11 
12             Customer customer = new Customer()
13             {
14                 FirstName = "firstName_test1",
15                 LastName = "Cascade",
16                 Age = 10
17             };
18 
19             Order order1 = new Order()
20             {
21                 OrderDate = DateTime.Now,
22                 Customer = customer
23             };
24 
25             Order order2 = new Order()
26             {
27                 OrderDate = DateTime.Now,
28                 Customer = customer
29             };
30 
31             //如果不加这一句:只添加Customer到数据,Order没有被添加到数据库
32             customer.Orders.Add(order1);
33             customer.Orders.Add(order2);
34 
35             //添加后customer.CustomerId被自动赋值
36             customerService.Add(customer);
37             Assert.IsNotNull(customerService.Find(customer.CustomerId));
38             Assert.IsNotNull(orderService.Find(order1.OrderId));
39             Assert.IsNotNull(orderService.Find(order2.OrderId));
40 
41             //先在内存中解除从属关系,使之成为orphan (孤儿)
42             //customer.Orders.Remove(order2); 
43 
44             customerService.Delete(customer);
45             Assert.IsNotNull(customerService.Find(customer.CustomerId));
46             Assert.IsNotNull(orderService.Find(order1.OrderId));
47             Assert.IsNotNull(orderService.Find(order2.OrderId));
48         }

 

以上用测试代码:
customer.Orders.Remove(order2); //先在内存中解除从属关系,使之成为orphan (孤儿)

使得

order2变成孤儿后,删除Customer时会引发异常如下异常,说明数据库不允许删除。

上面的单元测试没有通过,而是抛出异常:
Bug跟踪调试,会发现,删除失败的原因是,发生了如下异常:

{"DELETE 语句与 REFERENCE 约束\"FK_CustomerOrders\"冲突。该冲突发生于数据库\"NHibernateSampleAutoCreateTable\",表\"dbo.Order\", column ‘CustomerId‘。\r\n语句已终止。"}

 

补充:如果注释掉

customer.Orders.Remove(order2); //先在内存中解除从属关系,使之成为orphan (孤儿)

也即,不产生孤儿,级联删除是成功的。即使是MS SQL Server(其他数据库没测试过)级联操作设置为:"不执行操作",如下图:

 

 

测试二:cascade="all-delete-orphan"

Customer.hbm.xml:
  <class name="Model.Customer, Model"
         discriminator-value="0">
    <!--unsaved-value="http://www.mamicode.com/0" 主键表中不需要定义,而是需要在子表中定义-->
    <id name="CustomerId"
        column="CustomerId"
        type="int" 
        unsaved-value="0">
      <generator class="native" />
      <!-- unsaved-value used to be null and generator was increment in h2.0.3 -->
    </id>

    <!--version标签必须放在Id后面,否则出错-->
    <version name="Version"/>

    <property name="FirstName" >
      <column name="Firstname" length="50" not-null="true"/>
    </property>

    <property name="LastName" type="String">
      <column name="Lastname"/>
    </property>

    <property name="Age" type="int">
      <column name="Age"/>
    </property>

    <set name="Orders" table="Order" generic="true"
          inverse="true" cascade="all-delete-orphan">
      <key column="CustomerId" foreign-key="FK_CustomerOrders"/>
      <one-to-many class="Model.Order,Model"/>
    </set>
  </class>

 

再执行下面测试代码清单二:

 1         /// <summary>
 2         /// 测试联级删除
 3         /// Customer和Order配置了cascade="all-delete-orphan",
 4         /// 但是先在内存中解除从属关系,使之成为orphan (孤儿)
 5         /// </summary>
 6         [TestMethod]
 7         public void TestDeleteCustomer_Cascade_all_delete_orphan_RemoveOrderInMemery()
 8         {
 9             CustomerService customerService = new CustomerService();
10             OrderService orderService = new OrderService();
11 
12             Customer customer = new Customer()
13             {
14                 FirstName = "firstName_test1",
15                 LastName = "Cascade",
16                 Age = 10
17             };
18 
19             Order order1 = new Order()
20             {
21                 OrderDate = DateTime.Now,
22                 Customer = customer
23             };
24 
25             Order order2 = new Order()
26             {
27                 OrderDate = DateTime.Now,
28                 Customer = customer
29             };
30 
31             //如果不加这一句:只添加Customer到数据,Order没有被添加到数据库
32             customer.Orders.Add(order1);
33             customer.Orders.Add(order2);
34 
35             //添加后customer.CustomerId被自动赋值
36             customerService.Add(customer);
37             Assert.IsNotNull(customerService.Find(customer.CustomerId));
38             Assert.IsNotNull(orderService.Find(order1.OrderId));
39             Assert.IsNotNull(orderService.Find(order2.OrderId));
40 
41             //先在内存中解除从属关系,使之成为orphan (孤儿)
42             //customer.Orders.Remove(order2); 
43 
44             //customerService.Delete(customer);
45             Assert.IsNull(customerService.Find(customer.CustomerId));
46             Assert.IsNull(orderService.Find(order1.OrderId));
47             Assert.IsNull(orderService.Find(order2.OrderId));
48         }

 

 

 看图解:

 

 

结论:                    

                    cascade="all"                     cascade="all-delete-orphan"

      不产生孤儿          删父时联级删子                                 删父时联级删子

      产生孤儿             抛异常                                            删父时联级删子