我們在指定了數據庫表的關聯映射后，在刪除其中一方的的時候，提示了以下異常：deleted object would be re-saved by cascade (remove deleted object from associations): [entity.Associationinformation#7]

（注：entity.Associationinformation是實體類，7為設定的外鍵的值）

下面是我的多對一關聯情況：

1、實體類：

entity.Associationinformation和entity.Associationactivitylist，前者為one，后者為many。

Associationinformation.java:

public?class?Associationinformation?implements?java.io.Serializable?{ private?Integer?assoId; private?String?assoName; private?String?assoPosition; private?Integer?assoPersonNum; private?String?assoBuildDate; private?String?assoIntroduce; private?String?assoServiceObject; //一對一的社團負責人 private?Associationrespeople?assoResID; //一對多的社團活動 private?Set<Associationactivitylist>?assoActivity; //省略get/set方法 }

Associationactivitylist.java:

public?class?Associationactivitylist?implements?java.io.Serializable?{ private?Integer?activityId; private?String?activityName; private?String?activityPosition; private?Integer?activityPersonNum; private?String?activityTime; private?String?activityContent; private?Associationinformation?association; //省略get/set方法 }

2、映射文件：*.hbm.xml

Associationinformation.hbm.xml:

<hibernate-mapping><class?name="entity.Associationinformation"?table="associationinformation"?catalog="stu_association"><id?name="assoId"?type="java.lang.Integer"><column?name="AssoID"?/><generator?class="increment"?/></id><property?name="assoName"?type="java.lang.String"><column?name="AssoName"?length="20"?/></property><property?name="assoPosition"?type="java.lang.String"><column?name="AssoPosition"?length="20"?/></property><property?name="assoPersonNum"?type="java.lang.Integer"><column?name="AssoPersonNum"?/></property><property?name="assoBuildDate"?type="java.lang.String"><column?name="AssoBuildDate"?length="10"?/></property><!--??<property?name="assoResName"?type="java.lang.String"><column?name="AssoResName"?length="20"?/></property>--><property?name="assoIntroduce"?type="java.lang.String"><column?name="AssoIntroduce"?length="150"?/></property><property?name="assoServiceObject"?type="java.lang.String"><column?name="AssoServiceObject"?length="20"?/></property><!--?一對多的社團與社團活動?--><set?name="assoActivity"?table="associationactivitylist"><key?column="assoID"></key><one-to-many?class="entity.Associationactivitylist"/></set><!--?一對一的社團負責人?--><many-to-one?name="assoResID"class="entity.Associationrespeople"column="assoResID"lazy="false"cascade="all"unique="true"></many-to-one></class> </hibernate-mapping>

Associationactivitylist.hbm.xml:

<hibernate-mapping><class?name="entity.Associationactivitylist"?table="associationactivitylist"?catalog="stu_association"><id?name="activityId"?type="java.lang.Integer"><column?name="ActivityID"?/><generator?class="increment"?/></id><property?name="activityName"?type="java.lang.String"><column?name="ActivityName"?length="20"?not-null="true"?/></property><property?name="activityPosition"?type="java.lang.String"><column?name="ActivityPosition"?length="20"?not-null="true"?/></property><property?name="activityPersonNum"?type="java.lang.Integer"><column?name="ActivityPersonNum"?/></property><property?name="activityTime"?type="java.lang.String"><column?name="ActivityTime"?length="10"?not-null="true"?/></property><property?name="activityContent"?type="java.lang.String"><column?name="ActivityContent"?length="150"?/></property><!--?配置多對一關聯關系?--> <many-to-one?name="association"?class="entity.Associationinformation"?column="assoID"?cascade="all"> </many-to-one></class> </hibernate-mapping>

記得在Hibernate.cfg.xml中聲明映射文件的路徑：

<mapping?resource="entity/Associationinformation.hbm.xml"?/> <mapping?resource="entity/Associationactivitylist.hbm.xml"?/>

到這里就完成了一對多的關聯配置，然后在Action中寫Delete()方法：

public?String?deleteActivity(){ ... Transaction?tx?=?HibernateSessionFactory.getSession().beginTransaction(); assoActivityDao.delete(associationactivitylist); tx.commit(); HibernateSessionFactory.closeSession(); ... }

請注意，這樣寫的話，就會報出以上異常，如果沒有關聯關系，這樣寫是可以的。結合了網上的方法，解決方法如下：

1、刪除Set方的cascade：(缺點：子對象和父對象不能進行級聯更新，沒意義)

2、解決關聯關系后，再刪除（個人推薦）：

將Action中的方法改為：

public?String?deleteActivity(){ ... Associationactivitylist?associationactivitylist?=?assoActivityDao.findById(AssoID); Associationinformation?Association?=?associationactivitylist.getAssociation(); Association.getAssoActivity().remove(associationactivitylist); associationactivitylist.setAssociation(null); Transaction?tx?=?HibernateSessionFactory.getSession().beginTransaction(); assoActivityDao.delete(associationactivitylist); tx.commit(); HibernateSessionFactory.closeSession(); ... }

分別獲取到社團和社團活動對象后，利用remove方法解除關聯管理，再將one方的值設為null。

轉載于:https://blog.51cto.com/cfdeng/1755553

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