Laurie Harper wrote:
Scott Van Wart wrote:
We have a requirement that the user be prompted if any changes have
been made on a form, and they try to navigate away. I've divided
this up
Firstly, is the requirement to detect changes to the form compared to
how it was last rendered, or compared to how it was *originally*
rendered? I.e. do you have to be able to detect a difference in form
state across multiple requests?
Originally rendered. I need to render the hidden fields because it's a
multi-user system, and I have other mechanisms that maintain
concurrency--so by passing the fields back and forth as hidden, the
process doesn't get disrupted by someone else changing it in the
background (I can use my other methods of notifying the user that this
has happened).
Even then, all you really need is a Javascript object containing
key/value pairs describing each form property's starting value. You
shouldn't need to worry about server-side data types, collections, or
anything else; just 'form field X has value Y'.
There are a few things I need to worry about by design:
- Child items listed on a page, and their order.
- Multi-select dropdowns.
- Multiple checkboxes (this one actually wasn't as difficult as I
thought it was going to be).
- Map-based nested beans (someForm.someChild(4).whatever--ahh, a simple
key=value? Nope, whatever is a multi-checkbox).
Right now I'm halfway through my implementation of generating a lot of
stuff myself. Rather than using beanutils, I just add a @NavPrompt
annotation to each private member of my ActionForm that I want to
track. I've implemented basic ones (where I can just do
document.form.whatever.value != "..."), multi-selects (with a helper
method), multi-checkboxes (with a helper method), but I still need to do
nested beans and map-based beans.
I decided to do it this way rather than simple key/value pairs to keep
the JavaScript as simple as possible. It's also possible that with
better knowledge of JavaScript I could reduce the amount of framework I
need to write on the server, but writing Java code is far more fun than
learning--let alone writing--JavaScript IMHO :).
Thanks,
Scott
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