이 콘텐츠는 선택한 언어로 제공되지 않습니다.

21.4. Cascading Life Cycle

You can address the frustrations of the explicit call to save() by using cascades.

<set name="children" inverse="true" cascade="all">
    <key column="parent_id"/>
    <one-to-many class="Child"/>
</set>

<set name="children" inverse="true" cascade="all">
    <key column="parent_id"/>
    <one-to-many class="Child"/>
</set>

Copy to Clipboard

Toggle word wrap

This simplifies the code above to:

Parent p = (Parent) session.load(Parent.class, pid);
Child c = new Child();
p.addChild(c);
session.flush();

Parent p = (Parent) session.load(Parent.class, pid);
Child c = new Child();
p.addChild(c);
session.flush();

Copy to Clipboard

Toggle word wrap

Similarly, we do not need to iterate over the children when saving or deleting a Parent. The following removes p and all its children from the database.

Parent p = (Parent) session.load(Parent.class, pid);
session.delete(p);
session.flush();

Parent p = (Parent) session.load(Parent.class, pid);
session.delete(p);
session.flush();

Copy to Clipboard

Toggle word wrap

However, the following code:

Parent p = (Parent) session.load(Parent.class, pid);
Child c = (Child) p.getChildren().iterator().next();
p.getChildren().remove(c);
c.setParent(null);
session.flush();

Parent p = (Parent) session.load(Parent.class, pid);
Child c = (Child) p.getChildren().iterator().next();
p.getChildren().remove(c);
c.setParent(null);
session.flush();

Copy to Clipboard

Toggle word wrap

will not remove c from the database. In this case, it will only remove the link to p and cause a NOT NULL constraint violation. You need to explicitly delete() the Child.

Parent p = (Parent) session.load(Parent.class, pid);
Child c = (Child) p.getChildren().iterator().next();
p.getChildren().remove(c);
session.delete(c);
session.flush();

Parent p = (Parent) session.load(Parent.class, pid);
Child c = (Child) p.getChildren().iterator().next();
p.getChildren().remove(c);
session.delete(c);
session.flush();

Copy to Clipboard

Toggle word wrap

In our case, a Child cannot exist without its parent. So if we remove a Child from the collection, we do want it to be deleted. To do this, we must use cascade="all-delete-orphan".

<set name="children" inverse="true" cascade="all-delete-orphan">
    <key column="parent_id"/>
    <one-to-many class="Child"/>
</set>

<set name="children" inverse="true" cascade="all-delete-orphan">
    <key column="parent_id"/>
    <one-to-many class="Child"/>
</set>

Copy to Clipboard

Toggle word wrap

Even though the collection mapping specifies inverse="true", cascades are still processed by iterating the collection elements. If you need an object be saved, deleted or updated by cascade, you must add it to the collection. It is not enough to simply call setParent().

Report a bug

맨 위로 이동

이 콘텐츠는 선택한 언어로 제공되지 않습니다.

21.4. Cascading Life Cycle

자세한 정보

평가판, 구매 및 판매

커뮤니티

Red Hat 문서 정보

보다 포괄적 수용을 위한 오픈 소스 용어 교체

Red Hat 소개

Theme

Red Hat legal and privacy links

Red Hat legal and privacy links