Re: How to check for null values when using proxies?

Hi,

Schmidt wrote:
> Hi again Armin,
> 
> I saw some discussions regarding the AbstractIndirectionHandler class, maybe
> the method "public Object invoke" is outdated in the OJB version in use by
> me. I'm using OJB1.0.4 and the jar file date is 31/12/2005. Is that correct?

yep!

> Is there any other version available? If so, please point me out where can I
> get it.
> Thank you!

You can test the upcoming 1.0.5 version. The 1.0.5rc1 is stable but 
contain some specific query bugs. Details see this thread:

http://www.mail-archive.com/ojb-user%40db.apache.org/msg16078.html

regards,
Armin

> 
> 
> Schmidt wrote:
>> Hi Armin,
>>
>> Thank you for the answer.
>>
>> I'm using the 1.0.4 version. And the same problem happens with 1:n
>> associations as well. In the 1:n associations I set auto-retrieve="false"
>> and proxy="dynamic". As my classes do not implement interfaces, I'm using
>> CGLib as ProxyFactoryClass.
>> I debugged the source code and verified that the collection representing
>> the n side of the 1:n association is filled with proxy references. That's
>> good because the real object are not materialized, but when I check for
>> nullity, the result is false due to proxy references. The solution (ugly)
>> to bypass this problem is in the ProxyHelper.getRealObject method. But
>> this solution is invasive, proxies should be transparent.
>>
>> Another problem that came up after I started using proxies is in the
>> hierarchy mapping. I'm using just one table to map my class hierarchy. So,
>> this table has a CLASSNAME field to identify which class to load. In the
>> constructor of my base class I have a
>> setOjbConcreteClass(this.getClass().getName()) call. Before using proxies,
>> the class name was configured correctly. But after, instead of having the
>> real object class name, the application configures the classname field
>> using the proxy class name.
>>
>> I assume there should be something wrong with my mapping files or some
>> other point in my application. As said earlier, I believe proxies should
>> be transparent. Did someone here experience the same problems?
>>
>> Thank you again!
>>
>>
>> Armin Waibel wrote:
>>> Hi,
>>>
>>> Schmidt wrote:
>>>> Hi,
>>>>
>>>> Consider that an object A has an association with an object B. Also that
>>>> dynamic proxies are in use so that when object A is loaded, a proxy to B
>>>> is
>>>> created and the object B itself is not materialized. Sometimes, before
>>>> taking an action, I need to verify if there is a B object associated to
>>>> A.
>>>> This check is done as follows:
>>>> if (a.getB() == null) {...}
>>>>
>>>> The problem is that even if there isn't a B associated with A, OJB
>>>> returns
>>>> false because there is always a proxy between A and B. The check is
>>>> actually
>>>> done using the proxy reference which is always present.
>>>> How can we handle that?
>>>>
>>> Which version of OJB do you use? I try to reproduce this with the 
>>> current source (OJB_1_0_RELEASE branch) without success. If class 
>>> Article has a 1:1 relation to ProductGroup and I search for an Article 
>>> without a ProductGroup I get:
>>>
>>> Criteria c = new Criteria().addEqualTo("articleName", name + "without
>>> PG");
>>> q = QueryFactory.newQuery(ArticleWithReferenceProxy.class, c);
>>> Article br = (ArticleWithReferenceProxy) broker.getObjectByQuery(q);
>>> assertNotNull(br);
>>> assertNull(br.getProductGroup());
>>>
>>> Could it be that the association between A and B is a 1:n relation?
>>>
>>> regards,
>>> Armin
>>>
>>>> Thank in advance!
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>>>
>>>
>>
>