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HttpServlet.getLastModified

Dominic Paquette
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Joined: Dec 13, 2002
Posts: 64
Hi,
I am trying to figure out the use of the HttpServlet.getLastModified(HttpServletRequest req) method. The api says "Returns the time the HttpServletRequest object was last modified". I don't get this at all, if anyone has a link to an article or an explanation I would really appreciate.
Thanks in advance
Dominic
Peter den Haan
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Joined: Apr 20, 2000
Posts: 3252
The meaning of this method is to return the last time the resource represented by the servlet was modified. For example, if a GET for this servlet would return the contents of a file, you would override getLastModified() to return the modification date of the file. That way, browsers and proxies can find out whether they can use their own cached copy of the URL contents or have to download a new updated copy.
The default implementation of this method simply returns a negative number (-1 in fact), which should tell proxies and browsers never to cache the page (Microsoft Proxy is another story altogether though). After all, as far as the HttpServlet class knows you may be generating different content in doGet/doPost for every request, so it cannot make smart assumptions about how long content will remain valid for.
Overriding this method with something sensible will reduce network traffic and improve your site's responsiveness.
- Peter
Dominic Paquette
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Joined: Dec 13, 2002
Posts: 64
Thanks for the answer
Dominic
 
Don't get me started about those stupid light bulbs.
 
subject: HttpServlet.getLastModified