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Prevent caching of a JSP output

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This example shows how to prevent the browser to cache the content of a JSP.


Contents

the article

You will need to set the appropriate HTTP header attributes. see #for all the browsers

However, cache handling is tricky with IE brower. See http://support.microsoft.com/kb/q222064/. By adding a second HEAD is supposed to solve the problem! see #specifically for Internet explorer.

NOTE: Pragma: no-cache prevents caching only when used over a secure connection, Expires: -1 should do the job over unsecure connection.

for all the browsers 

<%
response.setHeader("Cache-Control","no-cache"); 
response.setHeader("Pragma","no-cache"); 
response.setDateHeader ("Expires", -1); 
%>

specifically for Internet explorer 

<%
response.setHeader("Cache-Control","no-cache"); 
response.setHeader("Pragma","no-cache"); 
response.setDateHeader ("Expires", -1);
%>
<HTML>
<HEAD> 
</HEAD> 
<BODY>
my page body
 
</BODY>
<HEAD> 
<META HTTP-EQUIV="PRAGMA" CONTENT="NO-CACHE"> 
<META HTTP-EQUIV="Expires" CONTENT="-1">
</HEAD> 
</HTML>

See Also

http://www.rgagnon.com/jsdetails/js-0014.html, http://www.rgagnon.com/jsdetails/js-0031.html, Real's Java How To

Comments from the users

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Cache is a problem - or even it's existence.

Caching of JSP output? ... as far as I know, JSP pages are compiled to servlets at the end of story... and saying JSP output caching would have to be related then to output stream caching (and we very want to have it here), anyway everyone know that it's about information transported within HTTP protocol that can be used by applications handling data exchange via mentioned protocol. Thing about JSPs and actually web page content (not only HTML, it can be image , text or anything else) caching is not that straight for real, caching can be done in many layers of transport model, lets imagine that we have: - server - proxy - client browser ( here it is also important what is the type of browser (IE,Gecko,WebKit etc. , they all try to apply standards, but if you start creating complicated software - difference will come out.) The most annoying caching is done via proxy servers (to decrease data transfers - typically in modem connection providers), in proxy "they" try generally to review HTTP headers and also data content (that last one isn't even legal in some countries). Browsers react with HTTP headers and content, but generally there is an order: HTML headers have higher priority than HTTP.

This article should rather be about "How to omit caching." - which is for real much more difficult task.

--86.163.174.232 17:41, 27 November 2008 (UTC)

back again

yep, i missed subject little, it IS actually about preventing cache of web pages. Basically, solution (the best in my opinion) is to operate on fake URI/URL changes (creating fake extensions that point to the same place or fake parameters), and (it might be surprising) setting all cache headers to "true" - we will control everything from one place then.

--86.163.174.232 17:48, 27 November 2008 (UTC)

one more :)

"Pragma" basically is deprecated and unofficial, better:

<meta http-equiv="CACHE-CONTROL" content="no-cache"/>

Anyway using two HEADERS is a scandal (!) , DOM tree is damaged then.

--86.163.174.232 17:54, 27 November 2008 (UTC)

corrupting pages? contribute

Hi 86.163.174.232, (could you sign with a name or an nickname if that's not 86.163.174.232? )

I don't know in the specific why in this case adding a second head solves, I feel that's a work around to some bug found by Rgagnon so it comes from experience.

I've come along with similar situations myself, in which you have to break the rules to make things work.

Sometimes when you find a bug in a program you don't always have the time or the authority to fix it. thus you need to invent a workaround. That's where lateral thinking comes along.

--DonGiulio 09:58, 28 November 2008 (UTC)

Dernell

Alakazaam-information found, problem solved, thakns!

--Dernell 23:48, 17 August 2011 (PDT)

Cathy

Woah nelly, how about them aeplps!

--Cathy 14:53, 18 August 2011 (PDT)

Christina

This piece was cogent, well-wrttien, and pithy.

--Christina 15:23, 18 August 2011 (PDT)

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