Ajax state history in coldfusion page - ajax

Question

I'm confused as to how to accomplish this. I have a page which, has a popup filter, which has some input elements and an "Apply" button (not a submit). When the button is clicked, two jquery .get() calls are made, which load a graph, a DataTables grid, photos, and miscellaneous info into four separate tabs. Inside the graph, if one clicks on a particular element, the user is taken to another page where the data is drilled down to a finer level. All this works well.
The problem is if the user decides to go back to the original page, but with the ajax generated graph/grid/photos etc. Originally I thought that I would store a session variable with the filter variables used to form the original query, and on returning to the page, if the session var was found, the original ajax call would be made again, re-populating the tabs.
The problem that I find with this method is that Coldfusion doesn't recognize that the session variable has been set when returning to the page using the browser's back button. If I dump out the session var at both the original and the second page, I can see the newly set var at the second page, and I can see it if I go to the original page through the navigation menu, but NOT if I use the back button.
SO.... from reading posts on here about ajax browser history plugins, it seems that there are various jquery plugins which help with this, including BBQ. The problem that I see with this approach is that it requires the use of anchor elements to trigger it, and then modifies the query string using the anchors' href attributes. I suppose that I could modify the page to include a hidden anchor.
My question, at long last is: is an ajax history plugin like BBQ the best way to accomplish this, or is there a way to make Coldfusion see the newly created session var when returning to the page via the back button? Or, should I consider re-architecting the page so that the ajax calls are replaced by a form submission back to the page instead?
Thanks in advance, as always.
EDIT: some code to help clarify things:
Here's the button that makes the original ajax calls:
<button id="applyFilter">APPLY</button>
and part of the js called on #applyFilter, wrapped in $(document).ready():
$('#applyFilter').click(function(){
// fill in the Photos tab
$.get('tracking/listPhotos.cfm',
{
id: id,
randParam: Math.random()
},
function(response){
$('#tabs-photos').html(response);
}
);
});
Finally, when the user calls the drill-down on the ajax generated graph, it uses the MaintAction form which has been populated with the needed variables:
function DrillDown() {
//get the necessary variables and populate the form inputs
document.MaintAction.action = "index.cfm?file=somepage.cfm&Config=someConfig";
document.MaintAction.submit();
}
and that takes us to the new page, from which we'd like to return to the first page but with the ajax-loaded photos.

Answer 1

The best bet is to use the BBQ method. For this, you don't have to actually include the anchor tags in your page; in fact, doing so would cause problems. This page: http://ajaxpatterns.org/Unique_URLs explains how the underlying process works. I'm sure a jQuery plugin would make the actual implementation much easier.
Regarding your other question, about how this could be done with session variables - I've actually done something similar to that, prior to learning about the BBQ method. This was specifically to save the state of a jqGrid component, but it could be easily changed to support any particular Ajax state. Basically, what I did was keep a session variable around for each instance of each component that stored the last parameters passed to the server via AJAX requests. Then, on the client side, the first thing I did was run a synchronous XHR request back to the server to fetch the state from that session variable. Using the callback method for that synchronous request, I then set up the components on my page using those saved parameters. This worked for me, but if I had to do it again I would definitely go with the BBQ method because it is much simpler to deal with and also allows more than one level of history.
Some example code based on your update:
$('#applyFilter').click(function(){
var id = $("#filterid").val(); // assumes the below id value is stored in some input on the page with the id "filterid"
// fill in the Photos tab
$.get('tracking/listPhotos.cfm',
{
id: id // I'm assuming this is what you need to remember when the page is returned to via a back-button...
//randParam: Math.random() - I assume this is to prevent caching? See below
},
function(response){
$('#tabs-photos').html(response);
}
);
});
/* fixes stupid caching behavior, primarily in IE */
$.ajaxSetup({ cache: false });
$.ajax({
async: false,
url: 'tracking/listPhotosSessionKeeper.cfm',
success: function (data, textStatus, XMLHttpRequest)
{
if (data.length)
{
$("#filterid").val(data);
$('#applyFilter').trigger('click');
}
}
});
This is what you need on the client-side to fetch the state of the photo list. On the server side, you'll need to add this modification to tracking/listPhotos.cfm:
<cfset session.lastUsedPhotoFilterID = URL.id>
And add this new one-line file, tracking/listPhotosSessionKeeper.cfm:
<cfif IsDefined("session.lastUsedPhotoFilterID")><cfoutput>#session.lastUsedPhotoFilterID#</cfoutput></cfif>
Together these changes will keep track of the last ID used by the user, and will load it up each time the page is rendered (whether via a back button, or simply by the user revisiting the page).