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From Robert Zeigler <>
Subject Re: Validation
Date Mon, 13 Apr 2009 23:38:27 GMT
Constraint information is available by examining the ObjEntity and  
DbEntity objects corresponding to the given object class.
I used this in the tapestry5-cayenne integration  module (t5cayenne)  
to have tapestry automatically pick up the relevant data constraints
Note: currently, t5cayenne supports the required constraint for any  
field type, the maxlength constraint for only string types, and no  
other constraints.  This is due to what I was interested in supporting  
at the time I wrote it rather than to some fundamental limitation; any  
remaining constraints will likely be added at some point in the  
future.  All of those caveats notwithstanding, you can take a look at  
the code for ideas:


On Apr 13, 2009, at 4/136:26 PM , Weddle, Anthony wrote:

> The documentation talks of removing validation as a concern of the  
> GUI,
> by using object validation that gets done before any commits. However,
> validation can continue to be needed in the GUI since it is always  
> nicer
> to let users know of problems early on (such as the maximum length  
> of a
> value, that a value must be a number or a value must not be null, as
> well as business validation). Is there some way to have database
> constraints visible to the GUI developer, perhaps through use of the
> class generation templates (by adding constraints as constants in the
> superclass, for example)?
> Thanks,
> Tony
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