Re: question about storing objects

Hi Armin,

thanks for help.

Just to be sure that I got the point: When there is a 'proxy="dynamic"' 
in the class-descriptor, proxies are always used when more than one 
object is queried?

I thought that proxies are only used when retrieving a collection 
through a relation (1:n or m:n, e.g. ShoppingCart.getArticles() - see 
below)...

Regards,

Abid

Armin Waibel schrieb:
> Hi Abid,
> 
> Abid Hussain wrote:
>> Hi again,
>>
>> I think this issue has to something with the materialization of 
>> objects (when using proxies). But I thought that proxies are only 
>> used, when retrieving a corresponding collection of an object (in 1:n 
>> and m:n relations, e.g. ShoppingCart.getArticles()...).
>>
>> What I'm doing when using findAll() (see below) is something like 
>> SELECT * FROM <tablename>. I thought, in this case no proxies are used???
>>
> 
> You are using dynamic proxies for all Account_2 objects:
> 
> <class-descriptor class="modulverwaltung.beans.Account_2"
>     table="ACCOUNT_2" proxy="dynamic">
> 
> The query result collection isn't a proxy object. Instead each result 
> object is a proxy object of persistence capable object (Account_2 
> object). In most cases this doesn't have an performance advantage.
> 
> If you now store each of these objects without materialization (e.g. 
> your log.debug() force the materialization of the object) OJB thinks 
> that the object didn't change and skip the update.
> 
> regards,
> Armin
> 
> 
>> Regards,
>>
>> Abid
>>
>>
>> Abid Hussain schrieb:
>>> Hi everybody,
>>>
>>> I have written a storeAll()-method in a dao to store all given 
>>> objects in one transaction (you find the code at the end of this mail).
>>>
>>> Now please have a look at the following lines of code:
>>> Account_2DAO dao1 = new Account_2DAO("DB1");
>>> Collection<Account_2> accounts = dao1.findAll(Account_2.class);
>>> logger.debug(accounts);
>>> Account_2DAO dao2 = new Account_2DAO("DB2");
>>> dao2.storeAll(accounts);
>>>
>>> As you see, that there are two daos initialized. The first (dao1) 
>>> retrieves all objects (using findAll()) from a database (DB1). The 
>>> second (dao2) stores all retrieved objects into another database (DB2).
>>> The findAll()-method works fine.
>>>
>>> But the storeAll()-method only works when the line of code
>>> logger.debug(accounts);
>>> is called. If not, no data is inserted.
>>>
>>> Any ideas what's going wrong (you find the class-descriptor file below)?
>>>
>>> Regards,
>>>
>>> Abid
>>>
>>>
>>> Code of storeAll():
>>> public void storeAll(Collection<T> valueObjects)
>>>         throws PersistentStoringException {
>>>
>>>     if (valueObjects != null) {
>>>         try {
>>>             broker.beginTransaction();
>>>             for (T valueObject : valueObjects) {
>>>                 broker.store(valueObject, ObjectModification.INSERT);
>>>             }
>>>             broker.commitTransaction();
>>>         } catch (Exception e) {
>>>             broker.abortTransaction();
>>>             throw new PersistentStoringException(
>>>                     "Error while storing objects.\n" + e);
>>>         } finally {
>>>             if (broker != null && !broker.isClosed())
>>>                 broker.close();
>>>         }
>>>     }
>>> }
>>>
>>> Class-descriptor of Account_2:
>>> <class-descriptor class="modulverwaltung.beans.Account_2"
>>>     table="ACCOUNT_2" proxy="dynamic">
>>>     <field-descriptor name="id" column="ID" primarykey="true"
>>>         autoincrement="true" sequence-name="Account_Id_Seq" />
>>>     <field-descriptor name="username" column="Username"
>>>         jdbc-type="VARCHAR" />
>>>     <field-descriptor name="role" column="Rolle" jdbc-type="VARCHAR" />
>>> </class-descriptor>
>>>
>>
> 
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-- 

Abid Hussain
Mail: [email protected]
Web: http://www.abid76.de