There is a way to discard sent content, but it is compiler specific.
SUN's JSP 0.92:
out varible is not PrintWriter but something like JspWriter (I can't
remember).
This JspWriter doesn't send content imediatelly, but stores it in
buffer. This
bufer can be cleaned by discard() method. It is done this way to provide
error
tracking. When exception is thrown, all content is discarded and another
JSP
page is called to generate html.
JSP should look like this:
...
<%
// clean output buffer
out.discard();
// send redirect
response.sendRedirect(resp.encodeRedirect("some URL"));
// exit from service()
return;
%>
...
Westaway Mike M píše:
> Yan,
>
> Thanks - that fixed it. There are a couple of subtle points worth noting:
>
> 1. From JSP it is impossible not to write anything to the PrintWriter after
> the redirect call because if the last characters of a JSP page are %> the
> page will not compile. i.e. There must be at least a CR/LF or space after
> the Java script.
>
> 2. This can be overcome by returning immediately after the redirect but, as
> you've shown, if the return call is not in a logical branch then the page
> will not compile because of unreachable code.
>
> Regards,
> Mike
>
> > ----------
> > From: Yan Pujante[SMTP:[EMAIL PROTECTED]]
> > Sent: 22 February 1999 16:49
> > To: [EMAIL PROTECTED]
> > Subject: Re: response.sendRedirect(<url>) raises java.io.Exception:
> > triedto write more than content length
> >
> > Rolland Crunk wrote:
> > >
> > > At 01:43 PM 2/19/99 +0000, Westaway Mike M wrote:
> > > >I'm running JSP 0.92 on sun sparc.
> > > >
> > > >any ideas why ?
> > > >
> > >
> > > Using the JavaWebServer or the servlet runner
> > (sun.servlet.http.HttpServer), right?
> > > I too have encountered this problem as well, but have no explaination as
> > to its
> > > cause. It seems to occur more frequently with the servlet runner, and I
> > haven't
> > > seen it happen if response.sendRedirect() is called from within a
> > servlet (as
> > > opposed to a jsp). I haven't encountered it with IBM WebSphere/Apache
> > and
> > > haven't tried any of the other jsp engines.
> > >
> > > So in response to your question, no ideas why, but if you or anyone else
> > solves
> > > this, please post to the list (as I will do if I stumble across the
> > answer).
> > >
> > > rc
> > >
> >
> > I too encountered the problem on several occasions. I am not sure this
> > is the real explanation of the problem, but here is what I have noticed.
> > When you use response.sendRedirect(), there shouldn't be any "write" or
> > "print" to the output stream (or writer), before or after this call. I
> > think that this call is not expecting anything to come with it because
> > you are specifying the address of the new page to fetch. Thus if you
> > write to the output stream, depending on the implementation, it will
> > notice that you are writing more than content length, because it is
> > supposed to be 0...
> >
> > Thus when using sendRedirect(), you should be carefull and write
> > somenthing like:
> >
> > service()
> > {
> > // code that DO NOT write on output stream
> >
> > if(my_condition_is_true)
> > {
> > response.sendRedirect(..);
> > return; // so that you are sure not to write something to the
> > output stream
> > }
> > }
> >
> > If you have a jsp page like that:
> > <HTML>
> > <BODY>
> > <%
> > if(my_condition_is_true)
> > {
> > response.sendRedirect(...);
> > return; // for the same reason!!!
> > }
> > %>
> > </BODY>
> > </HTML>
> >
> > Obviously this will raise the exception because <HTML><BODY> will be
> > sent to the output stream before the redirection... I agree that it is
> > not really easy to manage!
> >
> > Hope this helps.
> >
> > Yan
> >
> >
>
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