Java Enterprise Best Practices

Prevent Client-Side Caching for Dynamic Pages

Pages that are very dynamic—for instance, a page showing the result of a search based on user input—must not be cached anywhere. As described in Chapter 3, there’s a set of headers you can use to prevent caching of such a response. The problem for JSP pages is the same as described in the previous section, but luckily, the solution is the same as well: let the Controller set the headers for the requests it handles; let JSP pages that are invoked directly set their own headers; and for included pages, let the top-level page set them. Building on the example of a solution for the layout page scenario from the previous section, Example 9-10 shows a variable-setter page that adds caching headers to HashMap collections created by the layout page.

Example 9-10. A variable-setter page that adds caching headers

<%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %>
   
<c:set var="subTitle" scope="request" value="Page 1" />
<c:set target="${exp}" property="page1" value="0" />
                  <c:set target="headers" property="Cache-Control" 
  value="no-store, no-cache, must-revalidate, post-check=0, pre-check=0" />
                  <c:set target="headers" property="Pragma" value="no-cache" />

The page in this example adds the value 0 to the collection for expiration dates to ensure that the layout page sets it to a date far in the past. Even if another variable-setter page adds an expiration value for a date in the future, the value 0 is still used because it’s lower. The