1
我不知道为什么Hibernate会为每个实体1删除子表 而不是使用外键hibernate cascading delete,为什么不能在外键上删除一个?
一个删除这里的hibernate.cfg.xml文件(不,我不是下一个SO:-t
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.url">jdbc:hsqldb:file:testdb;shutdown=true</property>
<property name="hibernate.connection.driver_class">org.hsqldb.jdbcDriver</property>
<property name="hibernate.connection.username">sa</property>
<property name="hibernate.connection.password"></property>
<property name="hibernate.connection.pool_size">0</property>
<property name="hibernate.dialect">org.hibernate.dialect.HSQLDialect</property>
<property name="hibernate.show_sql">true</property>
<property name="hibernate.format_sql">true</property>
<property name="hbm2ddl.auto">auto</property>
<mapping file="entities/Question.hbm.xml"/>
<mapping file="entities/Answer.hbm.xml"/>
</session-factory>
Question.hbm.xml
<hibernate-mapping>
<class name="entities.Question">
<id name="id">
<generator class="native" />
</id>
<property name="title" not-null="true">
</property>
<property name="question" type="text" not-null="true">
</property>
<bag name="answers" inverse="true" cascade="all,delete-orphan" >
<key>
<column name="questionId" index="answer_questionId_idx" not-null="true"/>
</key>
<one-to-many class="entities.Answer" />
</bag>
<property name="created" update="false" >
<column name="created" not-null="true" index="answer_created_idx"></column>
</property>
<property name="lastUpdated">
<column name="lastUpdated" not-null="true" index="answer_lastUpdated_idx"></column>
</property>
</class>
</hibernate-mapping>
Answer.hbm.xml
<hibernate-mapping>
<class name="entities.Answer">
<id name="id">
<generator class="native" />
</id>
<property name="answer" type="text" not-null="true">
</property>
<property name="created" update="false" >
<column not-null="true" name="created" index="question_created_idx"></column>
</property>
<property name="lastUpdated" >
<column name="lastUpdated" not-null="true" index="question_lastUpdated_idx"></column>
</property>
<many-to-one name="question" column="questionId" not-null="true" update="false">
</many-to-one>
</class>
</hibernate-mapping>
有1个提问和2个答案在我的数据库,这个测试代码:
Session session = factory.openSession();
Transaction t = session.beginTransaction();
Question q = (Question) session.load(Question.class,1);
session.delete(q);
t.commit();
session.close();
我希望它生成SQL一样,
select .... from Questions where id = 1;
delete from Answers where questionId=1;
delete from Question where id=1;
也就是说,只是发出一个删除做级联删除的答案,而不是 它加载所有的答案,每发行一个答案删除,如:
select
question0_.id as id0_0_,
question0_.title as title0_0_,
question0_.question as question0_0_,
question0_.created as created0_0_,
question0_.lastUpdated as lastUpda5_0_0_
from
Question question0_
where
question0_.id=?
select
answers0_.questionId as questionId0_1_,
answers0_.id as id1_,
answers0_.id as id1_0_,
answers0_.answer as answer1_0_,
answers0_.created as created1_0_,
answers0_.lastUpdated as lastUpda4_1_0_,
answers0_.questionId as questionId1_0_
from
Answer answers0_
where
answers0_.questionId=?
delete from Answer where id=?
delete from Answer where id=?
delete from Question where id=?
如何COM e,有什么我可以做的吗?
编辑,作为对Nate Zaugg的回应,我可以通过在一对多键映射上设置on-delete =“cascade”来让db执行级联删除,我更想知道为什么hibernate会做什么它确实并没有在Answers表上删除一个,并且在我的映射中有些问题。
这并不回答这个问题。 – 2010-08-23 23:13:16
我相信它回答了“我能做些什么”部分! :) – 2010-08-23 23:15:27