hi!
this is just a workaround, but anyway:
can't you have a servlet receive the clients' requests and have the
servlet's if-modified functionality, the only thing this servlet does is
forwarding to your jsp (only in case it has been modified).
another option would be to check the date in your jsp, and in case it didn't
change return a 304 explicitly.
-mw
----- Original Message -----
From: "Tony LaPaso" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, June 04, 2002 9:28 AM
Subject: ??? Using JSPs to Send Not-Modified-Since Header ???
> Hi all,
>
> In looking at past posts, I'm afraid I know the horrible answer
> to this issue but I thought I'd ask just in case I missed
> anything.
>
> Let me start by saying I'm using Tomcat v4.0.4 beta 3.
>
> As you know, when a client (usually a web browser) has a cached
> version of a resource (usually a web page) it can send an
> "If-Modified-Since" header to the HTTP server. The server
> compares the time/date stamp specified in the header with that of
> the requested resource. If the resource has *not* been modified
> since the time specified in the "If-Modified-Since" header, the
> server sends back a 304 (Not-Modified) response, effectively
> telling the client (usually a web browser) that its cached
> version of the resource is still valid.
>
> When writing a servlet, it's easy to handle this sort of
> scenario. The javax.servlet.http.HttpServlet class has a
> "service()" method. This method first checks if the incoming HTTP
> method is a GET. If it is, the "service()" method proceeds to
> call the "getLastModified()" method of the servlet. As a
> developer, you can override "getLastModified()" to return a long
> value representing the last time the requested resource was
> changed. Depending on the value returned by "getLastModified()"
> (note that -1 is returned if you don't override the method) the
> "service()" method may simply return a 304, Not-Modified response
> rather than calling the servlet's "doGet()" method.
>
> Now, the $18.32 Question: How do you ensure "getLastModified()"
> is called in JSP?
>
> No, you cannot simply do this:
>
> <%!
> public long getLastModified() {
> return xxx;
> }
> %>
>
> The problem is that the above method will never be called by the
> container.
>
> I traced through some of the Tomcat/Catalina/Jasper code and it
> seems to me that the response code is being set to 200/OK very
> early on in the processing.
>
> I also took a cursory look at the JSP spec and didn't find any
> indication of setting a "Not-Modified" response code...so, I am
> thinking this is something that is (strangely) missing in the JSP
> specification. I have a JSP page that needs to update itself once
> per day. Therefore, it would be very handy to have the
> "getLastModified()" functionality enjoyed by servlet writers.
>
> Can anyone confirm this?
>
> Thanks...
>
>
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