And how is caching done if you can't query objects by identity? Or does
this question make even sense?
-Matej
Geoff hendrey wrote:
> Ohh my god yes!!!!
>
> I ran into all these problems in JDOMax, and they are
> all solved in Shades.
>
> I won't drop the name, but some very influential
> person on EJB and JDO specs now believe that exposing
> object identity in the form of API's was a mistake.
>
> I agree -- you will notice shades has no methods to
> retrieve an object by identity. Shades only has
> queries.
>
> -geoff
>
>
>
> --- Igor Vaynberg <[EMAIL PROTECTED]> wrote:
>
>> another interesting problem i find with identity in
>> full blown orms is that
>> it can cause a nasty cascade of loading object graph
>> when using "business"
>> identity instead of db identity.
>>
>> if you have school->semester->class relationships
>> and you do not want to
>> depend on db identity which is the "recommended" way
>> most likely you will
>> have
>>
>> class.equals(class other) {
>> this.name.equals(other.name
>> )&&this.semester.equals(other.semster); }
>> semester.equals(semester other) {
>> this.code.equals(other.code
>> )&&this.school.equals(other.school); }
>>
>> so now every time you equals/hashcode a class you
>> load the semester and the
>> school. given they they are loaded-by-id and might
>> be in 2nd level
>> cache....but still. this is the kind of troubles you
>> always have when
>> working on such a highly abstracted level that
>> doesnt always map properly to
>> the bare metal.
>>
>> -Igor
>>
>>
>> On 8/26/06, Geoff hendrey <[EMAIL PROTECTED]>
>> wrote:
>>> Sure - but honestly I don't want to convince
>> anyone
>>> they need Shades.
>>>
>>> One problem I found with JDO was that the
>>> PersistenceManager was not serializable. Another
>> is
>>> that detachment had to be handled explicitely.
>>>
>>> In Shades all pojo's are inherently detached.
>> Change
>>> tracking is automagic. The DatabaseSession is
>>> ultra-leightweight and totally appropriate for
>> keeping
>>> in a Session.
>>>
>>> A big innovation in Shades is how identity is
>> handled
>>> - that really solved a lot of problems for me
>> related
>>> to change of identity within transactions.
>> Identity is
>>> a much more fluid concept in Shades, due to the
>>> dynamic ORMapping interface, which you can even
>>> implement on the fly as an anonynmous inner class.
>>>
>>> To be clear, I found ways to make JDO work just
>> fine
>>> with Wicket. Certainly JDO was a huge step forward
>> in
>>> making it easier to use Pojo-based frameworks like
>>> Wicket.
>>>
>>> I blogged a bit on my motivation for Shades:
>>> http://notskateboarding.blogspot.com/
>>>
>>> -geoff
>>>
>>>
>>>
>>> --- Igor Vaynberg <[EMAIL PROTECTED]> wrote:
>>>
>>>> i glanced over the code - but i dont get it
>> after
>>>> the first glance. perhaps
>>>> you can explain what difficulties you hit when
>> using
>>>> wicket and an orm to
>>>> help us better understand.
>>>>
>>>> seems to me like you are trying to work with a
>> ui
>>>> connected to a persistence
>>>> layer - without a service layer in between. have
>> you
>>>> seen databinder which
>>>> glues wicket and hibernate together?
>>>>
>>>> also your point about wicket and tapestry -
>> wicket
>>>> is much more flexible
>>>> because it has IModel which gives you an extra
>> layer
>>>> of indirection that can
>>>> hide a lot of orm logic and make the code
>>>> cleaner/easier.
>>>>
>>>> -Igor
>>>>
>>>>
>>>> On 8/26/06, Geoff hendrey
>> <[EMAIL PROTECTED]>
>>>> wrote:
>>>>> Hi All,
>>>>>
>>>>> I was one of the early users of Wicket before
>> 1.0.
>>>> I
>>>>> did a lot of work to use Wicket with my JDO
>>>>> implementation JDOMax (no longer supported).
>> In
>>>> the
>>>>> process I learned a lot about why it is harder
>>>> than it
>>>>> has to be to use many ORM frameworks with
>> Wicket
>>>> and
>>>>> Tapestry.
>>>>>
>>>>> I'm a member of JSR 243 Java Data Objects
>> Experts
>>>>> Group, and I advocated hard within that spec
>> for
>>>> the
>>>>> "fixing" of the JDO spec with regard to
>>>>> non-transaction-write behavior, along with
>> Eric
>>>> Samson
>>>>> and others. The JDO group was receptive,
>> having
>>>>> gotten similar feedback from Howard Lewis Ship
>> of
>>>>> Tapestry. I believe this change will benefit
>>>> Wicket
>>>>> users, and make it much easier to use JDO 2.0
>> than
>>>> JDO
>>>>> 1.1, from Wicket.
>>>>>
>>>>> However, I still wasn't satisfied that it was
>>>> "easy"
>>>>> to do ORM from Wicket or Tapestry. So I
>> started a
>>>> new
>>>>> project, based on what I learned -- it's a
>> better
>>>> way
>>>>> to do ORM -- I call it Shades. Following the
>>>> wicket
>>>>> style,Shades works without any XML
>> configuration.
>>>>> Rather than make this any longer-winded, I
>> thought
>>>> I
>>>>> would just begin passing back some code,
>> showing
>>>> the
>>>>> Library sample application using Shades. The
>>>> attached
>>>>> zipfile is just the "library" folder from the
>>>> wicket
>>>>> sample applications. EditBook.java and
>>>>> LibrarySession.java have been altered to use
>>>> Shades
>>>>> for database access. LibraryORMDictionary.java
>> is
>>>> the
>>>>> only new file required.
>>>>>
>>>>> Please let me know what you think. Also, I do
>> not
>>>> have
>>>>> a website for Shades yet but I hope to find
>> the
>>>> right
>>>>> venue for open sourcing the code soon. (see
>>>> attached
>>>>> zip file 'library.zippo' with library-example
>>>> directory)
>>>>>
> -------------------------------------------------------------------------
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>> support
>>>> web services, security?
>>>>> Get stuff done quickly with pre-integrated
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>>>>> easier
>>>>> Download IBM WebSphere Application Server
>> v.1.0.1
>>>> based on Apache Geronimo
> === message truncated ===>
> -------------------------------------------------------------------------
>> Using Tomcat but need to do more? Need to support
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>> Get stuff done quickly with pre-integrated
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>> Download IBM WebSphere Application Server v.1.0.1
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>>
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