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From Ole Ersoy <ole.er...@gmail.com>
Subject Re: [LDAP DAS] Efficient Updating of Persisted Objects
Date Wed, 28 Mar 2007 05:34:02 GMT
David,

The LDAP DAS should work exactly the same way an RDB DAS would work.

So from the SDO point of view (Or your java bean point of view) it does 
not really
matter where the data is being persisted.

It could go to an XML file(s), an RDB, ADS, ERP, .....  It just depends on
which DAS the SDO datagraph is being serialized with.

I'm going to start writing the DAS design docs tomorrow, starting with
conventions used to perform CRUD against ADS for an SDO datagraph,
so hang in there.  I'm 99.9% sure that it does everything you want it to 
and more,
but the proof is in the pudding, and I would like you to be able to 
judge for yourself,
so I'll hurry it up.

Cheers,
- Ole


David Jencks wrote:
>
> On Mar 27, 2007, at 11:28 AM, Alex Karasulu wrote:
>
>> Ole,
>>
>> On 3/21/07, *Ole Ersoy* <ole.ersoy@gmail.com 
>> <mailto:ole.ersoy@gmail.com>> wrote:
>>
>>     Hey Guys,
>>
>>     Just wanted to see if anyone had any thoughts on handling updates
>>     to Java beans (Service Data Objects - but basically the same thing)
>>     persisted with ADS.
>>
>>     With Service Data Objects we create a datagraph that is then
>>     disconnected
>>     from it's persistence source and we can mutate it.  Then later we
>>     want to
>>     persist the graph.  Each object in the graph has a change
>>     summary, that
>>     stores the fields that were updated.
>>
>>  
>> This change summary is very interesting.  I had experimented with 
>> something
>> similar which David Jencks did not like too much.  Basically the 
>> modifier pattern
>> was being used to track modifications to attributes of entities.  It 
>> was tracking
>> the set of modify add, remove, and replace operations to perform on 
>> each attribute.
>
> What I didn't like was that you were keeping track of the 
> modifications outside the POJO-like data object itself in (IMO) very 
> hard to use helper objects, and you didn't write a framework.  I took 
> essentially the same idea and came up with something pretty similar to 
> jpa/jdo, where you have things that look like POJOs to the outside 
> world, but inside they keep track of how they relate to what's in the 
> persistent store.  The main differences to the ideas of jpa are that I 
> don't support disconnection and you have to do the enhancement 
> yourself.  In a non-locking not-transactional environment I'm not sure 
> exactly what disconnection means so this might not really be 
> accurate.  IIRC this stuff is all in the sandbox/triplesec-jacc2 branch.
>
> In the past I've tried to describe the kinds of ldap <> object 
> mappings I need and support in my framework but haven't understood 
> from Ole whether the DAS will offer similar capabilities.
>
> thanks
> david jencks
>
>>
>>  
>>
>>     This makes it possible to only update objects that have been
>>     changed, and
>>     we only need to update the fields that were changed. 
>>
>>  
>> Exactly this is what I was doing in this one admin API I had in 
>> triplesec.
>>
>>  
>>
>>     However, I think the DirContext will overwrite the entire
>>     object during the bind operation, rather than updating specific
>>     fields
>>     on the object.
>>
>>  
>> Hmmm with heirarchical services in JNDI you should not be using 
>> bind().  You
>> should be using the createSubcontext() and modifyAttributes() methods 
>> instead.  You
>> might want to go through the JNDI tutorial for LDAP just to get a 
>> good feel for how to
>> work with non-flat namespaces using JNDI.  Namely with LDAP you don't 
>> need to
>> rebind the object with a modification to an attribute.  This is what 
>> the modify
>> operations are for.
>>
>> http://bsd.cs.cofc.edu/Java/Javadocs1.5/api/javax/naming/directory/DirContext.html#modifyAttributes(javax.naming.Name

>> <http://bsd.cs.cofc.edu/Java/Javadocs1.5/api/javax/naming/directory/DirContext.html#modifyAttributes%28javax.naming.Name>,

>> int, javax.naming.directory.Attributes)
>>
>>
>>  
>>
>>     Initially I  was thinking that the object's attributes (primitive
>>     properties - not references to other objects)
>>     would be serialized and made into directory attributes.  But I
>>     think a
>>     LDAP ObjectClass schema that corresponds to the
>>     object's class (The class of the object we are persisting) would
>>     have to
>>     be generated and stored along with the instance.
>>
>>     This might lead to performance improvments, if doable...?
>>
>>     Thoughts?
>>
>>  
>> Hmmm I think some of your premisses in this question may be due to 
>> considering the use
>> of bind() instead of using modifyAttributes() and 
>> createSubcontext().  If you use these methods
>> I think there is no further preformance issue to consider.  WDYT?
>>  
>> Alex
>>  
>>
>>
>


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