Re: Question about localObjects()

[Borut Bolčina <bo...@najdi.si>]

Hello,

I was searching the archives on what would be the best way to move 
objects between data contexts. Beside 
http://cwiki.apache.org/CAYDOC/moving-objects-between-contexts.html I 
found this thread and as I don't have much experience in moving objects, 
I wonder what the current recommendation is? Are there different 
approaches for some scenarios (web application, standalone application) 
or is there one best way of doing it?

Thanks!
Borut



On 30.12.2005 7:20, Andrus Adamchik wrote:
> Hi Marcin,
>
> I was on vacation and didn't read the mailing list for a while. During 
> that time I came up with a solution that is closer to what DataContext 
> does. It is somewhat similar to what you suggest, but relies on 
> ClassDescriptor.copyProperties. It does not involve serialization or 
> class generation. I just checked in this code to CVS, it will be in 
> the 12/30/2005 nightly build. Let me know how this worked.
>
> Andrus
>
>
> On Dec 23, 2005, at 5:57 AM, Marcin Skladaniec wrote:
>
>> Hi Andrus !
>>
>> On 19/12/2005, at 8:21 PM, Andrus Adamchik wrote:
>>
>>
>>>
>>> This is another omission in the API. I'll make sure this is added in 
>>> the next milestone. For now you can do something like that 
>>> (untested!) -
>>>
>>> Persistent clone = (Persistent) Util.cloneViaSerialization(object);
>>> clone.setObjectContext(otherContext);
>>> otherContext.getGraphManager().registerNode(clone.getObjectId(), 
>>> clone);
>>>
>>
>> I investigated this bit of code and found that PersistentObjects are 
>> not Serializable...
>> I made an ugly, but working approach to make them serializable. Added 
>> few lines to client-superclass.vm:
>> (You can see that two first methods are only modified methods from 
>> CayenneDataObject)
>>
>> private void writeObject(ObjectOutputStream out) throws IOException {
>>        out.writeInt(getPersistenceState());
>>
>>        switch (getPersistenceState()) {
>>            // New, modified or transient or deleted - write the whole 
>> shebang
>>            // The other states (committed, hollow) all need just 
>> ObjectId
>>            case PersistenceState.TRANSIENT:
>>            case PersistenceState.NEW:
>>            case PersistenceState.MODIFIED:
>>            case PersistenceState.DELETED:
>>
>>                out.writeObject(getPropertyHashtable());
>>                break;
>>        }
>>
>>        out.writeObject(getObjectId());
>>    }
>>
>>    private void readObject(ObjectInputStream in) throws IOException,
>>            ClassNotFoundException {
>>        this.setPersistenceState(in.readInt());
>>
>>        switch (getPersistenceState()) {
>>            case PersistenceState.TRANSIENT:
>>            case PersistenceState.NEW:
>>            case PersistenceState.MODIFIED:
>>            case PersistenceState.DELETED:
>>
>>                setPropertyMap((Map)in.readObject());
>>                break;
>>            case PersistenceState.COMMITTED:
>>            case PersistenceState.HOLLOW:
>>                   this.setPersistenceState(PersistenceState.HOLLOW);
>>                // props will be populated when required (readProperty 
>> called)
>>                setPropertyMap(new HashMap());
>>                break;
>>        }
>>
>>        this.setObjectId((ObjectId) in.readObject());
>>
>>        // DataContext will be set *IF* the DataContext it came from 
>> is also
>>        // deserialized. Setting of DataContext is handled by the 
>> DataContext
>>        // itself
>>    }
>>
>>
>>
>>     public Map getPropertyMap() {
>>         Hashtable t=new Hashtable() ;
>> #foreach( $attr in ${objEntity.DeclaredAttributes} )
>>         if (get${stringUtils.capitalized($attr.Name)}() != null) {
>>             
>> t.put(${stringUtils.capitalizedAsConstant($attr.Name)}_PROPERTY, 
>> get${stringUtils.capitalized($attr.Name)}());
>>         }
>> #end
>> #foreach( $rel in ${objEntity.DeclaredRelationships} )
>>         if (get${stringUtils.capitalized($rel.Name)}() != null) {
>>             
>> t.put(${stringUtils.capitalizedAsConstant($rel.Name)}_PROPERTY, 
>> get${stringUtils.capitalized($rel.Name)}());
>>         }
>> #end
>>         return t;
>>     }
>>     
>>     public void setPropertyMap(Map map) {
>>     #foreach( $attr in ${objEntity.DeclaredAttributes} )
>>         if 
>> (map.containsKey(${stringUtils.capitalizedAsConstant($attr.Name)}_PROPERTY)) 
>> {
>>             set${stringUtils.capitalized($attr.Name)}( 
>> ($importUtils.formatJavaType(${attr.Type}))  
>> map.get(${stringUtils.capitalizedAsConstant($attr.Name)}_PROPERTY));
>>         }
>>     #end
>>     }
>>
>>
>> My idea :
>> - add get/setPropertyMap() methods with empty bodies to PersistentObject
>> - add get/setPropertyMap() methods to client-superclass.vm
>> - add read/writeObject() to PersistentObject
>> and voila, serialization, and (and therefore localObjects()) works 
>> for 3t
>> What do you think ? Is there a better solution ?
>>
>> Cheers
>> Marcin Skladaniec
>>
>>
>

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