Explanation of this header cache code

[dmjpro]

<%response.addH eader("Pragma", "No-cache");
response.addHea der("Cache-Control", "no-cache");
response.addDat eHeader("Expire s", -1);
%>


what is the purpose of this code ...


plz explain me in details ....


thanx in advance .....

[abctech]

<%response.addH eader("Pragma", "No-cache");
response.addHea der("Cache-Control", "no-cache");
response.addDat eHeader("Expire s", -1);
%>


what is the purpose of this code ...


plz explain me in details ....


thanx in advance .....

Hello,
At the top of every JSP the above header attributes are used to prevent caching.
Now I don't know in depth about 'Caching' but whatever little I know I'll share it with you, for the details we'll have to wait for an expert opinion :)

Well,
Http headers used for cache control to prevent the web pages from being cached by the browser and proxy server.

response.setHea der("Cache-Control","no-cache"); //prevents disk caching (HTTP 1.1)
response.setHea der("Pragma","n o-cache"); //prevents disk caching (HTTP 1.0)
response.setDat eHeader ("Expires", 0); //prevents caching at the proxy server

I'm not really sure about response.addDat eHeader("Expire s", -1);
I think its to be used for web pages which have information subject to change promptly, such pages do remain in the disk cache of the IE to be used when the user hits back/forward but when the user actually sends a request for such a page the browser fetches the updated version from the web server.

[dmjpro]

lot of thanx

well ...

i think response.addHea der("Expires",-1) means that the cache control prevention for only that browsing session ..

as early as the browsing session exits then the cache control starts again

am i right ...

manyyyyy thanx again

[r035198x]

I will just say that in response.addHea der("Expires",-1)

-1 is the expiration time. The value -1 means that there is no expiration time set.

[dmjpro]

thanx for ur reply ......

one more thing i want to know that where the cache happens ...

i mean does it happen in local memory or into the disk

my problem occures as long as the same browsing session remains..
after the browsing sessoin ends then the updated page shown

plz help me out ...
again thanx in advance

[abctech]

thanx for ur reply ......

one more thing i want to know that where the cache happens ...

i mean does it happen in local memory or into the disk

my problem occures as long as the same browsing session remains..
after the browsing sessoin ends then the updated page shown

plz help me out ...
again thanx in advance

I think its the disk, isn't our surfing history stored in those 'History','Temp orary Internet Files' and some other such temporary folders on our hard drive?

P.S:
By the way, can I ask you in which class/interface is the addDateHeader(S tring,int) method located?

[r035198x]

By the way, can I ask you in which class/interface is the addDateHeader(S tring,int) method located?

javax.servlet.h ttp.HttpServlet Response

[abctech]

javax.servlet.h ttp.HttpServlet Response

Thanks,
Got it.

Interface- 'HttpServletRes ponse'
public void addDateHeader(j ava.lang.String name,long date);

dmjpro-
Here's a link I just came across regarding preventing caching of web pages(but its only for IE)

[dmjpro]

thanx a lot ....