Preserve The Current Page And Sort Across Sessions (patch included)

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imported from sf tracker
id 980723
submitted by David E - halcy
http://sourceforge.net/support/tracker.php?aid=980723
====

Here is another enhancement for the project. It adds
the attribute
"preserveSortAndPage" to the table tag in both EL and
standard versions.
The idea is that (at least from usage on our own site)
someone can sort a
large list and get it exactly as they like it, then perhaps
navigate away to
something else, and would like to when they return see
it the same way they
left it (potentially, the data could change). However
navigating back to it
they likely wouldnt have the request parameters needed
to sort it as it was,
so when the preserveSortAndPage attribute is set to
true, the current
sort/page/sort order (and potentially previous sort/sort
order) are all
saved into session attributes named the same as they
would as request
parameters.

When the tag is executed and the preserveSortAndPage
attribute is set to
true it will first check the request parameters for the
necessary
information, and if it returns null from there it will
fallback to session,
then eventually to defaults.

There is an inherent limitation to this, if someone had a
list somewhere
else on the site and it was using the same name
variables for its list, and
it also had the preserveSortAndPage attribute set the
variables could clash,
thats a limitation of the parameter encoder. I thought
about tweaking the
parameter encoder to also encode perhaps the current
request.uri which would
be unique to that list because it would be on a different
page from another
list, however we use struts and when I watched that
value with the debugger
it was just pointing to my base tiles layout.. (which was
surprising to
me).. so that wouldnt uniquely define the list either. So
my conclusion is
it should be a documented limitation for people that
want to use this
feature, they need to name their lists differently if they
are going to use
them across the site.