| I’m using the <ora:noCache> action described in Chapter 12 in your book, but Internet Explorer caches the responses anyway.What can I do to prevent caching? |
| Answer: Unfortunately, IE is infamous for ignoring cache headers and it seems like different versions of IE have different bugs in this area. Using the <ora:noCache/> custom action from Chapter 12 in the main JSP file shouldwork, but I can’t guarantee that since some browsers are buggy. One thing you can try is to use the value 0 or -1 instead of 1 for Expires. Before changing the code for <ora:noCache>, you can test with a scriptlet: <%
response.addHeader("Pragma", "No-cache");
response.addHeader("Cache-Control", "no-cache");
response.addDateHeader("Expires", -1");
%>
Another trick is to use the corresponding meta tags both at the top and at the bottomof the JSP page: <HTML>
<HEAD>
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="-1">
</HEAD>
<BODY>
The content ...
</BODY>
<HEAD>
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
<META HTTP-EQUIV="Expires" CONTENT="-1">
</HEAD>
</HTML>
This is, of course, invalid HTML but it’s a solution MS provides for this bug, see http://support.microsoft.com/support/kb/articles/Q222/0/64.ASP On the server side, to make sure that changes to the JSP file take effect immediately, you should always use the include action, i.e. <jsp:include>. This has nothing to do with browser caching, though. See the book and my Top Ten Tips article for more on the different ways to include page fragments and what happens when the included fragment is changed. Finally, if everything else fails, you can make sure each request is done with a unique URL by adding a dummy query string parameter, e.g. a timestamp like “?ts=123456″. A browser can not use a cached result if the query string is different from the one for the cached result. |
Hans Bergsten
Software Adventures
