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From Alexandru Popescu <the.mindstorm.mailingl...@gmail.com>
Subject Re: [mapping] mapping enhancement supporting GRFT54
Date Mon, 16 Jan 2006 20:14:31 GMT
#: Christophe Lombart changed the world a bit at a time by saying (astral date: 1/16/2006 9:48
PM) :#
> On 1/16/06, Alexandru Popescu <the.mindstorm.mailinglist@gmail.com> wrote:
>> #: Christophe Lombart changed the world a bit at a time by saying (astral date: 1/16/2006
5:25 PM) :#
>> > Concerning issue http://issues.apache.org/jira/browse/GRFT-54,
>> > Why do you think about the following mapping  :
>> >
>> > <class-descriptor className="xxx.File" jcrNodeType="nt:file" >
>> >         <field-descriptor fieldName="path" path="true" />
>> >         <subnode-descriptor   jcrName="jcr:content" ... >
>> >             <field-descriptor fieldName="mimeType" jcrName="jcr:mimeType"
... />
>> >             <field-descriptor fieldName="encoding"
>> > jcrName="jcr:encodiging" .../>
>> >             <field-descriptor fieldName="data" jcrName="jcr:data" ... />
>> >             ....
>> >         </subnode-descriptor>
>> > </class-desciptor>
>> >
>> > the "subnode-descriptor" is there to create a new subnode called
>> > "jcr-content" which will contains some object attributes like
>> > mimeType, encoding, ...
>> >
>> > Anyway, I like the "converter" idea. At least, it quite easy to
>> > implement it for the fd.
>> > Converters for cd already exists but they need to be review. But now,
>> > we have to think about how to use the converters for the bd.
>> >
>> > (I don't speak now on inheritance, we can start this discussion later).
>> >
>>
>> The proposal you are making is quite nice for this particular example. But I cannot
say how
>> extensible it is (by looking at it I would say that it is pretty much the bean-descriptor).
I would
>> like that before introducing more descriptors to be sure that a new one will be able
to fill in a
>> whole range of solutions and not just a particular one. The same applies to the existing
ones.
> 
> ok - can we create a new jira issues which will contain all use cases.
> It is quite difficult to remember all possibilities.
> 
> Thanks
> 
>

Not sure what you are asking :-(. Is your question about creating a JIRA issue for each of
the 
suggested improvements? If yes, than I would say that I would prefere having it in the ML
than 
directly on JIRA, and upon concluding adding a JIRA with only the conclusion. But if you think
JIRA 
is better to handle this discussion than go ahead and open the necessary enhancement requests.

cheers,

./alex
--
.w( the_mindstorm )p.


>>
>> ./alex
>> --
>> .w( the_mindstorm )p.
>>
>> >
>> > On 1/14/06, Alexandru Popescu <the.mindstorm.mailinglist@gmail.com> wrote:
>> >> #: Christophe Lombart changed the world a bit at a time by saying (astral
date: 1/13/2006 11:20 AM) :#
>> >> > On 1/13/06, Alexandru Popescu <the.mindstorm.mailinglist@gmail.com>
wrote:
>> >> >
>> >> >> considering the GRFT54 example, you will write:
>> >> >>
>> >> >> <bean-descriptor fieldName="file"
>> >> >>                  converterClass="NtFileConverter" />
>> >> >>
>> >> >> and NtFileConverter will be responsible for creating the nt:file
node structure. Same mechanism will
>> >> >> work for fetching.
>> >> >>
>> >> >
>> >> > I like this idea but how set the mapping rules for each attributes
?
>> >> > I expect the field-descriptor, bean-descriptor & collection-descriptor
>> >> > are still necessary if we uses the convertClass.
>> >> >
>> >>
>> >> This is a very good question to which unfortunately i don't have a good
answer. While a predefined
>> >> converter knows how to deal with a limitted set of properties/subnodes,
on the other side (e.g. on
>> >> objects world) those properties may come from really complex expressions.
>> >> There are a few possible approaches to solving this, but for the moment
none of them satisfies me:
>> >> - have the object implement an interface which responds to the needs of
the converter
>> >> (may be considered bad because it ties the object to the ojcrm tool)
>> >> - have the description provided through the same mechanisms of fd, bd or
cd
>> >> (may be considered bad because the mapping becomes complex, and changes
in some way the semantics of
>> >> fd, bd and cd)
>> >> - create/reuse a object graph navigation language
>> >> (may be considered bad because the user should learn a new/the user should
use a new `languageยด)
>> >> - have the converter provide extension points so that in special cases an
user may extend it to
>> >> extract the values/populate the values
>> >>
>> >> Example:
>> >> 1/ in the simplest case where the object provides accessors to the object
properties according to
>> >> the needs of the converter than you don't need to detail the mapping (the
node property paths and
>> >> subnodes paths maps directly to object properties)
>> >> 2/ in more complex cases where the object needs special manipulation in
order to provide/to write
>> >> object properties, than the user should extend the converter and provide
access to those properties
>> >>
>> >> what do you think?
>> >>
>> >> ./alex
>> >> --
>> >> .w( the_mindstorm )p.
>> >>
>> >>



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