When I delete some objects whicc get from the relation, it throws the following exception.

could not delete collection: [mo.umac.eticketing.common.valueobject.discount.DiscountCriteriaVO.discountCriteriaValueVOs#1180]

public void preDelete() throws AppException {
int size = getDiscountCriteriaVOs().size();
for(int i=0;i<size;i++) {
DiscountCriteriaVO discountCriteriaVO = (DiscountCriteriaVO)getDiscountCriteriaVOs().remove(0);
discountCriteriaVO.delete();
}
}

/**
* @hibernate.bag lazy="true"
* @hibernate.collection-key column="criteriaId"
* @hibernate.collection-one-to-many class="DiscountCriteriaValueVO"
*/
public List getDiscountCriteriaValueVOs() {
return discountCriteriaValueVOs;
}

public void preDelete() throws AppException {
for(int i=getDiscountCriteriaValueVOs().size()-1;i>=0;i--) {
DiscountCriteriaValueVO discountCriteriaValueVO = (DiscountCriteriaValueVO)getDiscountCriteriaValueVOs().remove(i);
discountCriteriaValueVO.delete();
}
}

I don't know why it can be delete.

If delete the discountVO, the child of discount will not be deleted. The hibernate only set the value of the foreign key to be null. In fact, it should delete the object in the database.

/**
* @hibernate.bag lazy="true" cascade="delete-orphan"
* @hibernate.collection-key column="discountId"
* @hibernate.collection-one-to-many class="DiscountCriteriaVO"
*/
public List getDiscountCriteriaVOs() {
return discountCriteriaVOs;
}