Do i prevent the output of my JSP.........

Question

Hi Friends...... How do I prevent the output of my JSP or Servlet pages from being cached by the browser? Thanks............

Chintan Rathod · Answer

1) setHeader (String name, String value) Sets a response header with the given name and value. Cache-Control The Cache-Control header can be used to expire content immediately or disable caching altogether. The value of this header determines whether cached pagelet/portlet content can be shared among different users. The Cache-Control header can contain the following values: public Allows any cached content to be shared across users with identical sets of preferences using the same portal server. This value should be used whenever possible. private Tells the portal server not to share cached content. The User ID is added to the cache key so that a separate copy is retained in the cache for each individual user. This value should only be used to protect sensitive information, for example, an e-mail inbox portlet. (User settings can also make public content effectively private.) max-age=[seconds] Specifies the maximum amount of time that an object is considered fresh. Similar to the Expires header, this directive allows more flexibility. [seconds] is the number of seconds from the time of the request that the object should remain fresh. must-revalidate Tells the cache that it must obey any freshness information it receives about an object. HTTP allows caches to take liberties with the freshness of objects; specifying this header tells the cache to strictly follow your rules. no-cache Disables caching completely and overrides Web Service editor settings. Neither the client nor the Portal Server responds to subsequent requests with a cached version. In JSP, use the setHeader method to configure the Cache-Control header: response.setHeader("Cache-Control","public"); %> The JSP example below expires the content immediately using the maximum age header. response.setHeader("Cache-Control","max-age=0"); %> Following will not "store" or "cache" response.setHeader("Cache-Control","no-store"); %> In .NET, the Cache-Control header is accessed through the System.Web.HttpCachePolicy class. To set the header to public, private or no-cache, use the Response.Cache.SetCacheability method. Response.Cache.SetCacheability(HttpCacheability.Public); Pragma: The Pragma general-header field is used to include implementation- specific directives that might apply to any recipient along the request/response chain. All pragma directives specify optional behavior from the viewpoint of the protocol; however, some systems MAY require that behavior be consistent with the directives. Pragma = "Pragma" ":" 1#pragma-directive pragma-directive = "no-cache" | extension-pragma extension-pragma = token [ "=" ( token | quoted-string ) ] HTTP/1.1 caches SHOULD treat "Pragma: no-cache" as if the client had sent "Cache-Control: no-cache". No new Pragma directives will be defined in HTTP. Note: because the meaning of "Pragma: no-cache as a response header field is not actually specified, it does not provide a reliable replacement for "Cache-Control: no-cache" in a response 2) response.setDateHeader ("Expires", long value); Expires: An application can also set the Expires header to enable caching, when the expiration date is a specific time instead of an interval. For heavily loaded pages, even setting short expires times can significantly improve performance. Sessions should be disabled for caching. setDateHeader ("Expires", now + 15000); %> Count: so, full code to implement is.... response.setHeader("Cache-Control","no-store"); response.setHeader("Pragma","no-cache"); response.setDateHeader ("Expires", 0); %> Thank you.

Vikas Mishra · Answer

Thanks............

Satyapriya Nayak · Answer

Hi Vikas, You will need to set the appropriate HTTP header attributes to prevent the dynamic content output by the JSP page from being cached by the browser. Just execute the following scriptlet at the beginning of your JSP pages to prevent them from being cached at the browser. You need both the statements to take care of some of the older browser versions. response.setHeader("Cache-Control","no-store"); //HTTP 1.1 response.setHeader("Pragma\","no-cache"); //HTTP 1.0 response.setDateHeader ("Expires", 0); //prevents caching at the proxy server %> Refer http://www.jguru.com/faq/view.jsp?EID=377 Thanks

Do i prevent the output of my JSP.........

Answers (3)