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Posted to ojb-user@db.apache.org by David Zejda <dv...@atlas.cz> on 2004/07/20 11:51:37 UTC
OJB capable SortedSet [Re: The collection has no foreignkeys, says
XDoclet]
> You have a missing quotation mark for the collection-class attribute,
thanks for a quick reply - sorry about my blindness
> Btw, I don't think that TreeSet works as the collection-class, you
> should use one of the classes provided by OJB. Same for using SortedSet
> as the variable type - you have to use Set here. You shouldn't need to
> specify TreeSet as the collection-class anyway as OJB maintains the
> order that the objects are inserted. So you should be fine with
>
> /**
> * @ojb.collection element-class-ref="oit.ucase.DepositIndulgence"
> * foreignkey="deposit_id"
> * auto-retrieve="true"
> * auto-update="true"
> * auto-delete="true"
> */
> private java.util.Set indulgences = new java.util.TreeSet();
OK, but imagine the scenario:
1) TreeSet created, a few objects inserted by program (and ordered).
2) Persisted.
3) Retrieved from DB, OJB creates it's own (non-sorted) Set, inserts
objects in correct order.
4) Several more objects inserted by program. I guess, they will not be
sorted (and it's a problem)..
possible solutions:
a) use non-sorted set as a persistent one and sort it independently on
persistence (by wrapper SortedSet or somehow..)
b) create OJB-capable SortedSet and use that one as e collection-class
> Tom
David
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Re: OJB capable SortedSet [Re: The collection has no foreignkeys,
says XDoclet]
Posted by David Zejda <dv...@atlas.cz>.
Thomas Dudziak wrote:
> David Zejda wrote:
>
>>> You have a missing quotation mark for the collection-class attribute,
>>
>>
>> thanks for a quick reply - sorry about my blindness
>
>
> No problem, happens to all of us :-)
>
>>> Btw, I don't think that TreeSet works as the collection-class, you
>>> should use one of the classes provided by OJB. Same for using
>>> SortedSet as the variable type - you have to use Set here. You
>>> shouldn't need to specify TreeSet as the collection-class anyway as
>>> OJB maintains the order that the objects are inserted. So you should
>>> be fine with
>>
>>
>> >
>> > /**
>> > * @ojb.collection element-class-ref="oit.ucase.DepositIndulgence"
>> > * foreignkey="deposit_id"
>> > * auto-retrieve="true"
>> > * auto-update="true"
>> > * auto-delete="true"
>> > */
>> > private java.util.Set indulgences = new java.util.TreeSet();
>>
>> OK, but imagine the scenario:
>>
>> 1) TreeSet created, a few objects inserted by program (and ordered).
>> 2) Persisted.
>> 3) Retrieved from DB, OJB creates it's own (non-sorted) Set, inserts
>> objects in correct order.
>> 4) Several more objects inserted by program. I guess, they will not be
>> sorted (and it's a problem)..
>>
>> possible solutions:
>> a) use non-sorted set as a persistent one and sort it independently on
>> persistence (by wrapper SortedSet or somehow..)
>> b) create OJB-capable SortedSet and use that one as e collection-class
>
>
> Then I'd say, go for option b, e.g. create a ManageableTreeSet or
> DTreeSet (depending on your requirements). Have a look at the source of
> ManageableHashSet and DSetImpl for pointers.
> If you'd be willing to, we could include your class in OJB as it
> probably is useful for other people, as well.
There is nothing special on it, but if you say, it's here..
BTW I think it would be better to send it to ojb-dev, but currently I'm
not a subscriber and it seems to be useless to subscribe only becouse of
such nit..
/* Copyright 2002-2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.ojb.broker.util.collections;
import org.apache.ojb.broker.ManageableCollection;
import org.apache.ojb.broker.PersistenceBroker;
import org.apache.ojb.broker.PersistenceBrokerException;
import java.util.Collection;
import java.util.Comparator;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.Iterator;
/**
* is a utility class. provides a SortedSet that addionally implements
* the ManageableCollection interface. This class may be used
* as a type for collection attributes.
*
* @author <a href="mailto:dvid@atlas.cz">David Zejda<a>
*/
public class ManageableTreeSet extends TreeSet implements
ManageableCollection
{
/** Creates a new instance of ManageableSortedSet */
public ManageableTreeSet(Collection c)
{
super(c);
}
/** Creates a new instance of ManageableSortedSet */
public ManageableTreeSet(Comparator c)
{
super(c);
}
/** Creates a new instance of ManageableSortedSet */
public ManageableTreeSet(SortedSet s)
{
super(s);
}
/** Creates a new instance of ManageableSortedSet */
public ManageableTreeSet()
{
super();
}
/**
* add a single Object to the Collection. This method is used
during reading Collection elements
* from the database. Thus it is is save to cast anObject to the
underlying element type of the
* collection.
*/
public void ojbAdd(Object anObject)
{
super.add(anObject);
}
/**
* adds a Collection to this collection. Used in reading Extents
from the Database.
* Thus it is save to cast otherCollection to this.getClass().
*/
public void ojbAddAll(ManageableCollection otherCollection)
{
super.addAll((ManageableTreeSet) otherCollection);
}
public void afterStore(PersistenceBroker broker) throws
PersistenceBrokerException
{
//do nothing
}
/**
* returns an Iterator over all elements in the collection. Used
during store and delete Operations.
* If the implementor does not return an iterator over ALL
elements, OJB cannot store and delete all elements properly.
*
*/
public Iterator ojbIterator()
{
return super.iterator();
}
}
> Tom
David
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Re: OJB capable SortedSet [Re: The collection has no foreignkeys,
says XDoclet]
Posted by Thomas Dudziak <to...@first.fhg.de>.
David Zejda wrote:
>> You have a missing quotation mark for the collection-class attribute,
>
> thanks for a quick reply - sorry about my blindness
No problem, happens to all of us :-)
>> Btw, I don't think that TreeSet works as the collection-class, you
>> should use one of the classes provided by OJB. Same for using
>> SortedSet as the variable type - you have to use Set here. You
>> shouldn't need to specify TreeSet as the collection-class anyway as
>> OJB maintains the order that the objects are inserted. So you should
>> be fine with
>
> >
> > /**
> > * @ojb.collection element-class-ref="oit.ucase.DepositIndulgence"
> > * foreignkey="deposit_id"
> > * auto-retrieve="true"
> > * auto-update="true"
> > * auto-delete="true"
> > */
> > private java.util.Set indulgences = new java.util.TreeSet();
>
> OK, but imagine the scenario:
>
> 1) TreeSet created, a few objects inserted by program (and ordered).
> 2) Persisted.
> 3) Retrieved from DB, OJB creates it's own (non-sorted) Set, inserts
> objects in correct order.
> 4) Several more objects inserted by program. I guess, they will not be
> sorted (and it's a problem)..
>
> possible solutions:
> a) use non-sorted set as a persistent one and sort it independently on
> persistence (by wrapper SortedSet or somehow..)
> b) create OJB-capable SortedSet and use that one as e collection-class
Then I'd say, go for option b, e.g. create a ManageableTreeSet or
DTreeSet (depending on your requirements). Have a look at the source of
ManageableHashSet and DSetImpl for pointers.
If you'd be willing to, we could include your class in OJB as it
probably is useful for other people, as well.
Tom
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