Prevent page clients from being cached_html/css_WEB-ITnose

Prevent the page client from being cached

In order to quickly display the requested page to the user, many browsers will store the web page from the server in the client's cache. If the user makes multiple
requests Access the same web page on the server side, and the web page already exists in the client's cache, then the browser only needs to obtain the web page from the cache
, and does not need to request access to the web page on the remote server
browser Side-side caching technology is suitable for saving server-side static web pages and web pages that do not contain sensitive data. In the following situation, the server often
does not want the client to be cached by the browser:
(1) The web page contains information that will be updated at any time. Dynamic content, because if the browser displays a web page in the local cache to the user, it may display an expired web page
(2) The web page contains sensitive data, such as a specific user's bank account information, email content, because If the browser saves the web page in the local cache
it may be accessed by other unauthorized users
The server-side HttpServlet can prohibit the client from caching the web page by setting a specific HTTP response header,
response .addHeader("Pragma","no-cache");
response.setHeader("Cache-Control","no-cache");
response.setHeader("Expires","0");
The "Parama" option is suitable for browsers using HTTP1.0. In HTTP1.1, the "Cache-Control" option is used to determine whether the client can cache web pages. If the value is
"no-cache "Then the client will not save the web page generated by the Servlet in the local cache. Both HTTP1.0 and HTTP1.1 support the "Expires" option
Therefore, all browsers can recognize this option. The "Expires" option is used Set the expiration time of the web page. If it is 0, it means it will expire immediately. If the user repeatedly requests to access the
website, the browser should obtain the latest web page data from the server each time