[jdom-interest] Child-Parent patch - Ideas.

Jason Hunter jhunter at xquery.com
Thu Feb 5 17:52:54 PST 2004

New: I checked in Rolf's changes.  You can do a diff between the CVS 
tags "before_rolf" and "after_rolf" to see the effect of his changes. 
The zips will also work.

I'd still like feedback.  I just checked them in since they seem 
reasonable to me.


Jason Hunter wrote:

> Rolf sent in this change a while back, and I just integrated it with the 
> latest CVS code but haven't checked it in.  I'm curious what other 
> people think of it as an approach.  Rolf's description below explains 
> its justification.
> I invite people to compare the CVS HEAD (get it from CVS or at 
> http://jdom.org/head.zip) versus the source at http://jdom.org/rolf.zip. 
>  Comments welcome.  Which way should we go?
> -jh-
> Rolf Lear wrote:
>> I have had a look at the Child/Parent thing.
>> Personally, I don't think the Idea has been taken far enough, so I 
>> played around with the concept, and "normalised" some of the 
>> redundancies.
>> Firstly, I converted the Child interface into an Abstract class that 
>> deals with ALL Parent/child relationships for the Child role, 
>> including detaching, cloning, set/getParent (and holds the parent 
>> instance field).
>> I also implemented getDocument at the Child Class level (all children 
>> have the same mechanism for getting the Document).
>> Next, I added the method "getDocument" to the Parent Interface... and 
>> parent can getDocument, including the Document class which has "return 
>> this;" in the getDocument().
>> Finally, I changed the ContentList class substantially. elementData is 
>> now called childData, and is of type Child[] instead of Object[]. The 
>> ContentList owner is now of type Parent instead of Object. I have 
>> added a method canContain to the Parent interface, and thus the actual 
>> Parent object determines what content is allowed in the contentlist, 
>> so instead of add(int,Text), add(int,Element), add(int,CDATA), 
>> add(int,ProcessingInstruction), etc, there is just add(int, Child).
>> In doing all of the above, I have cut large amounts of 
>> redundant/duplicated code, simplified the relationships, and thrown 
>> away "special cases". The only downside I can see in terms of 
>> "functionality" is that some of the exceptions are thrown with less 
>> specialised messages...
>> Please have a look, and comment on the concept. Note, that this is 
>> only possible by converting Child to an abstract class instead of an 
>> interface.
>> Rolf
>> <<jdom_child.zip>>
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