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:
http://code.google.com/p/tapestry5-cayenne/source/browse/trunk/tapestry5-cayenne-core/src/main/java/com/googlecode/tapestry5cayenne/services/CayenneConstraintGenerator.java
Robert
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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