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From Sylvain Wallez <>
Subject Re: [cforms] Uniqueness of IDs and ValidationAware forms
Date Mon, 06 Jun 2005 07:54:17 GMT
Reinhard Poetz wrote:

> Sylvain Wallez wrote:


>> The main principle of the Ajax stuff is that each part of the page 
>> that can be updated asynchronously (not necessarily a widget) must be 
>> fully contained in a tag (span, div, input, whatever) with a unique 
>> id. In the case of widgets, this id is the value of 
>> widget.getRequestParameterName().
> ok, sounds easy


>> We therefore need a distinct id for validation errors, which can be 
>> e.g. {widget.requestParameterName}.$error, which uses the same 
>> $-prefix convention as Java bytecode for synthetic names (those 
>> generated by the program).
> this means I have to register the errors in the form object in a 
> similar way as it is done with widgets (addWidgetUpdate() and 
> getUpdatedWidgets()) and enhance the generateValidationError() and 
> flushRoot(ValidationError error) methods so that they send the bu: 
> tags with the replacement information. Right?


>> Update of the validation error is then linked to a change of its 
>> associated widget. For now, change detection is a boolean thing 
>> (changed / unchanged) but we may go to something more fine-grained in 
>> the future (e.g. value changed / error changed / selection list 
>> changed etc).
> your explanations have made me think of the uniqueness of names. As 
> long as you only have forms of a different type on the page the names 
> are unique, at least if you set the id attribute in the form tag of 
> the form definition.
> But if you use the same form definition more than once, you'll run 
> into problems. These become obvious if you run the same form in two 
> different portlets. If the form uses a field of type "date" the date 
> chooser is confused because there are two fields with the same id. 
> IIUC this must be a problem for Ajax too. Right?

Yes. Note that a form can have an id, although it is generally left 
empty. This form id can be used to ensure global uniqueness in a 
composite page. But this id must come from the outside environment of 
the form, to allow e.g. the same form to be used several times in a page.

Hmm... we need a unique id generator that produces short and valid ids.


Sylvain Wallez                        Anyware Technologies  
Apache Software Foundation Member     Research & Technology Director

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