I have read a lot of discussion on forms best practices in the list
archives, but I have some questions that I don't think have been
addressed:
1. PropertyUtils.copyProperties() only performs a shallow copy,
according to it's JavaDoc description. So I think this means that the
form properties with nested objects could be referring to the same
object instance that is actually one of the properties of a business
object. Now, doesn't that mean that business objects are being modified
without being mediated by the Action object? In other words, you don't
get the chance to look at the input data and decide whether or not to
reject it or use only some of it to change the state of the model.
2. If the scope of an ActionForm is "request", then even if you
pre-populate it before displaying a form to the user, it's data will be
gone when the user submits the form (because it's a new instance). So
if you have properties with nested values they cannot be set on form
submission, because the parent property no longer exists. Isn't this a
common problem, or is it just me?
For example, I have a Map-backed ActionForm that has a variable set of
fields, each with nested properties, determined at runtime. When I
submit the form, if it's request-scoped, those nested properties can't
be set because the map is now empty.
eg: the property "value(dynamicItem).name" can't be set, because it
requires a call to MyForm.getValue("dynamicItem").setName() -- but
MyForm.getValue("dynamicItem") returns null because the map is now
empty.
Do most people use session-scoped forms for this? then what if the user
has two windows, and decides to show use the same form to edit
different records in each?
A potential solution:
I'm kind of torn over whether I think this is a good idea or not, but I
wrote a wrapper object that I'm using as a general value object. it
solved both problems because 1) it uses recursive calls to
PropertyUtils.copyProperties() to create a "deep" representation of the
original (business) object using Maps and Lists (and String or Boolean
as the "leaf" datatypes). and for problem 2) it returns a new (empty)
instance when asked for a property that doesn't exist. so
getValue("dynamicItem").setName() always works, even if there is no
value for the key "dynamicItem".
Now is somebody going to tell me that was a waste of time because there
are simple answers to the two questions above? I hope so, because it
would be nice to simplify, and this might be a bit slow. What do you
think? I would appreciate any input.
However I end up doing it, I don't want to write many ActionForm
classes, I want to use one flexible one in all (or at least most)
cases, and I want to be able to dynamically create copied
representations of my business objects that can be used as form
properties without having to manually code a String-and-Boolean-only
value object for each business object. call me lazy, but I don't think
there's any disadvantage in doing the view component totally
dynamically.
thanks!
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