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JSP - Back Button Problems

Vishwa Kumba
Ranch Hand

Joined: Aug 27, 2003
Posts: 1064
What kind of problems can I expect with the back button in a typical web application involving transactions? In my application, a Customer could browse the website and buy a few items.(typical basket/checkout kind of functionality)

Say, I have a page with a basket containing 2 items. I add a 3rd item, now my basket shows 3 items. I could press back button in the browser, go back to my previous page. See that there are only 2 items and add another item. But now my basket will show 4 instead of 3. Is this a valid reason why we would handle the back button?

I could handle the back button in the foll. ways:

1. Disable the back button in the browser including the short cut keys and
also disable right click mouse button(selecting the floating back menu option)
2. Capture the back button thru a suitable javascript handler and submit a special form containing a special hidden field present in the JSP, so that the server-side recognizes this as a back button action and redirects the user to the current page again.
3. Ignore the back button altogether and make my entire application appear in a child window with no menu options, so that the user will be able to use only the application navigation menus/buttons.
(I may have to disable the right-click mouse event also).

What the pros and cons of the above 3 options?...Are there any other options apart from the above?

thanks,
Vishwa
David O'Meara
Rancher

Joined: Mar 06, 2001
Posts: 13459

4) None of the above. Design operations with page caching in mind.

The other option you're missing is that alt-back arrow also goes back. I use this without thinking.

It's a little more complicated to manage a site without blocking the back button, but it's possible and typically doesn't cause the javascript-hell I've seen in other applications.

Firstly you need to define the pages that shouldn't be cached by the browser and set them up with the required no-cache functionality. If you're not too worried some people make the whole site uncachable.

Secondly, you need to understand POST and GET and make sure you POST data and GET pages. Don't be tempted to combine the two.

The third step I use is I guess what I'd call a non-displaying-processing-servlet, and it's your best tool for protecting yourself against the back button.

It's a servlet that looks like this:

That's it. The only special bit is that it doesn't display a page after, it uses sendRedirect to delegate display to another page. The trick here is that since the POST doesn't result in a page, refreshing doesn't result in data being reposted. Also, since (presumably) the previous page wasn't cached and was requested via GET, it automatically gets refreshed by the browser.

There are still a few down sides to it, such as using the back button to go back to a non-cached POSTed page, but it's easier to manage and design around than trying to create a site that effectively blocks the back button.

In my opinion, anyway.
Hope this helps,
Dave.
Vishwa Kumba
Ranch Hand

Joined: Aug 27, 2003
Posts: 1064
Thanks Dave,
Sorry for not replying to you earlier. Yes, your idea did help us.
 
I agree. Here's the link: http://aspose.com/file-tools
 
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