Christopher Schultz schrieb am 01.12.2008 um 14:15:31 (-0500):
> Michael Ludwig wrote:
Hi Chris,
thanks for your reply. Sorry for not getting back earlier.
> Is this the filter you wrote in your other thread?
Yes.
> Maybe you are not printing your output at the right time. Or maybe you
> aren't flushing buffers at the right time.
See below.
> > I can also make the included HTML page display correctly despite
> > the filter by resorting to res.getOutputStream() instead of
> > res.getWriter() in my servlet code. But it should work either way,
> > shouldn't it?
>
> That is definitely odd.
The source code of DefaultServlet, which serves static HTML, explains
this behaviour.
> > public ServletOutputStream getOutputStream() throws IOException {
> > // getResponse().getOutputStream();
> > return this.stream;
> > }
> >
> > public PrintWriter getWriter() throws IOException {
> > // getResponse().getWriter();
> > return this.writer;
> > }
> >
> > You see there are calls to the underlying response object, which are
> > commented out. When I comment these lines back in, everything works
> > fine. No need to flush the buffer before the include, to resort to
> > SOS instead of PW, or to JSP instead of HTML.
>
> Then you should definitely do this ;)
Yes, these calls are needed.
> > So these calls on the underlying object seem to have something to do
> > with the behaviour observed. Can anyone explain what's going on?
>
> I'll bet that since the response hasn't had the writer/outputstream
> choice made, the DefaultServlet makes a random decision. If your
> wrapper response has made a different choice, things can get fouled
> up.
This is the relevant chunk from serveResource() in DefaultServlet (which
serves static HTML, among other things):
try {
ostream = response.getOutputStream();
} catch (IllegalStateException e) {
// If it fails, we try to get a Writer instead if we're
// trying to serve a text file
if ( (contentType == null)
|| (contentType.startsWith("text"))
|| (contentType.endsWith("xml")) ) {
writer = response.getWriter();
} else {
throw e;
}
}
A filter intercepting the response and deviating it in its own buffers
has to make sure the call to getOutputStream() fails when it has already
issued a PrintWriter.
Michael Ludwig
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