[英]Hibernate: bidirectional one-to-many foreign key constraint fails
I want to implement a one-to-many relation using Hibernate (in Java). 我想使用Hibernate(在Java中)实现一对多关系。 I have two entities:
我有两个实体:
Experiment
has many ExperimentGroups
. Experiment
有许多ExperimentGroups
。 I tried to configure this one-to-many relation, the way the official Hibernate document recommends: http://docs.jboss.org/hibernate/core/3.6/reference/en-US/html/example-parentchild.html#example-parentchild-cascades 我尝试按照官方Hibernate文档建议的方式配置此一对多关系: http : //docs.jboss.org/hibernate/core/3.6/reference/zh-CN/html/example-parentchild.html#例如-父子-级联
My config file: 我的配置文件:
<class name="ExperimentImpl" table="Experiment">
<id name="id" type="int" column="id">
<generator class="increment" />
</id>
<!-- One to Many -->
<set name="experimentGroups" table="ExperimentGroup"
lazy="false" fetch="select" cascade="all" inverse="true">
<key>
<column name="Experiment_id" not-null="true" />
</key>
<one-to-many class="ExperimentGroupImpl" />
</set>
</class>
<class name="ExperimentGroupImpl" table="ExperimentGroup">
<id name="id" type="int" column="id">
<generator class="increment" />
</id>
<many-to-one name="experiment" class="ExperimentImpl" fetch="select">
<column name="Experiment_id" not-null="true" />
</many-to-one>
</class>
Adding a new ExperimentGroup
to an Experiment
works fine, but deleting an Experiment (and all of its ExperimentGroups) causes an exception: 将新的
ExperimentGroup
添加到Experiment
可以正常工作,但是删除Experiment(及其所有ExperimentGroup)会导致异常:
Cannot delete or update a parent row: a foreign key constraint fails (
testdb
.ExperimentGroup
, CONSTRAINTFK9C71D86238B5500C
FOREIGN KEY (Experiment_id
) REFERENCESExperiment
(id
))无法删除或更新父行,外键约束失败(
testdb
。ExperimentGroup
,约束FK9C71D86238B5500C
外键(Experiment_id
)参考Experiment
(id
))
My ExperimentDAO code looks like this: 我的ExperimentDAO代码如下所示:
public void deleteExperiment(Experiment experiment)
throws DAOException
{
Session session = null;
Transaction t = null;
try{
session = HibernateUtil.getSessionFactory().openSession();
t = session.beginTransaction();
session.delete(experiment);
t.commit();
session.flush();
session.close();
}catch (HibernateException e)
{
e.printStackTrace();
if (t != null)
t.rollback();
if (session != null)
session.close();
throw new DAOException(e, "Could not delete Experiment");
}
}
EDIT: The DAO code to create an Experiment and ExperimentGroup: 编辑: DAO代码创建一个Experiment和ExperimentGroup:
public Experiment createExperiment(String name, String description, RegisteredUser owner)
{
Transaction tx = null;
Session session = null;
try
{
session = HibernateUtil.getSessionFactory().openSession();
tx= session.beginTransaction();
ExperimentImpl e = new ExperimentImpl();
e.setName(name);
e.setDescription(description);
e.setOwner(owner);
owner.getOwnedExperiments().add(e);
session.save(e);
tx.commit();
session.flush();
session.close();
return e;
} catch (HibernateException ex )
{
if (tx != null)
tx.rollback();
if (session!=null)
session.close();
throw ex;
}
}
public ExperimentGroup createAndAddExperimentGroup(Experiment experiment, String experimentGroupName, Date startDate, Date endDate) throws ArgumentException
{
Transaction t = null;
Session session = null;
try
{
session = HibernateUtil.getSessionFactory().openSession();
t = session.beginTransaction();
ExperimentGroupImpl g = new ExperimentGroupImpl();
g.setEndDate(endDate);
g.setStartDate(startDate);
g.setName(experimentGroupName);
g.setExperiment(experiment);
experiment.getExperimentGroups().add(g);
g.setExperiment(experiment);
session.save(g);
session.update(experiment);
t.commit();
session.flush();
session.close();
return g;
}catch(HibernateException e)
{
if (t!=null)
t.rollback();
if (session!= null)
session.close();
throw e;
}
}
There are many other properties for an Experiment, like the name, description etc., which I have removed from the config file, because they don't have an impact on the one-to-many relation. 实验中还有许多其他属性,例如名称,描述等,这些属性已从配置文件中删除,因为它们对一对多关系没有影响。
Any suggestion? 有什么建议吗? What did I wrong?
我怎么了
I am under the impression that you are trying to delete a detached entity that you manually created. 我的印象是,您正在尝试删除手动创建的分离实体。 I would try to use the primary key of the Experiment you want to delete, and load before actually deleting it:
我会尝试使用您要删除的实验的主键,并在实际删除它之前加载:
session = HibernateUtil.getSessionFactory().openSession();
t = session.beginTransaction();
ExperimentImpl persistentExperiment = session.load(ExperimentImpl.class, experiment.getId());
session.delete(persistentExperiment);
t.commit();
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