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Date: Mon, 05 Sep 2005 21:10:47 -0500
From: Antonio Gallardo <agallardo@agssa.net>
Organization: AG Software, S. A.
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To: dev@cocoon.apache.org
Subject: Re: SQLTransformer
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Leszek Gawron wrote:

> Antonio Gallardo wrote:
>
>> I will suggest OJB instead - http://db.apache.org/ojb/.
>
> On the contrary I strongly recommend Hibernate :)
>
>> I was working on a hibernate the last weeks and I need to say that I 
>> prefer OJB. Here 2 samples:
>>
>> 1-When using a java List for a collection inside a bean, in Hibernate 
>> the table need an additional field to manage the order of the table 
>> rows! What is that?
>
> That is the persistent order of your collection. A list needs to know 
> what is the sequence of it's child beans. How do you do it in OJB?

Using "orderby" attribute - 
http://db.apache.org/ojb/docu/guides/repository.html#collection-descriptor
There is no need of an extra field.

>
>> 2-I don't want in my database more fields than what I need, so let 
>> replace the Java List witth a Java Set --> then I meet a new problem: 
>> cforms binding use jxpath and jxpath don't work with Sets. jxpath 
>> throws an Unsupported Operation Exception! Boom!
>
> strange:
>
> <fb:context xmlns:fb="http://apache.org/cocoon/forms/1.0#binding"
>             xmlns:fd="http://apache.org/cocoon/forms/1.0#definition"
>             xmlns:ci="http://apache.org/cocoon/include/1.0"
>             path="/" >
>     <fb:repeater id="questionDefinitions" parent-path="." 
> row-path="questionDefinitions" direction="load">
>         <fb:identity>
>             <fb:value id="id" path="id"/>
>         </fb:identity>
>         <fb:on-bind>
>             <fb:value id="questionName" path="name"/>
>             <fb:value id="questionCategory" path="category/name"/>
>         </fb:on-bind>
>     </fb:repeater>
> </fb:context>
>
> In this case I have bound SurveyDefinition.questionDefinitions 
> collection and it works.

In my case, I met the Unsupported Operation Exception in jxpath using 
@direction="save" not while loading a not with a repeater, but using a 
cform multivalue field.

>
>> I wonder how people using hibernate deal with this situations. The 
>> 1st shows me a poor database desing and the second a restriction to 
>> use cforms at all! 
>
> I still do not get why this is a poor database design. In hibernate 
> you can use:
>
> 1. unordered set
> 2. a treeset ordered with Comparable contract
> 3. a List which has a persistent order of your choice.
>
> Only the third choice for obvious reasons needs an indexing column.

What is the obvious reason? IMO, an additional index field shows a poor 
database design.

Best Regards,

Antonio Gallardo.