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From "Bill Barker" <wbar...@wilshire.com>
Subject RE: Response not flushed before RD.forward() returns
Date Fri, 20 Jan 2006 02:11:49 GMT
 

> -----Original Message-----
> From: Jan Luehe [mailto:Jan.Luehe@Sun.COM] 
> Sent: Thursday, January 19, 2006 5:57 PM
> To: tomcat-dev@jakarta.apache.org
> Subject: Response not flushed before RD.forward() returns
> 
> Consider the following code snippet of a servlet's service() method:
> 
>   public class DispatcherServlet extends HttpServlet {
> 
>     public void service(HttpServletRequest req, 
> HttpServletResponse res)
>         throws IOException, ServletException {
> 
>       
> request.getRequestDispatcher("/target").forward(request, response);
> 
>       try {
>           Thread.currentThread().sleep(60000);
>       } catch (Exception ex) { }
>     }
> 
> where "target" prints some output to the response.
> 
> The code currently returns the output printed by "target" only after
> DispatcherServlet's service() method has finished, instead of right
> before RD.forward() returns.
> 
> This seems to be in violation of the Servlet Spec, which has this:
> 
> SRV.8.4 ("The Forward Method"):
> 
>   Before the forward() method of the RequestDispatcher interface
>   returns, the response content must be sent and committed, and closed
>   by the servlet container.
> 
> The code at the end of o.a.c.core.ApplicationDispatcher.doForward()
> looks like this:
> 
>         // This is not a real close in order to support error 
> processing
>         if ( log.isDebugEnabled() )
>             log.debug(" Disabling the response for futher output");
> 
>         if  (response instanceof ResponseFacade) {
>             ((ResponseFacade) response).finish();
>         } else {
>             // Servlet SRV.6.2.2. The Resquest/Response may have been
> wrapped
>             // and may no longer be instance of RequestFacade
>             if (log.isDebugEnabled()){
>                 log.debug( " The Response is vehiculed using 
> a wrapper: "
>                            + response.getClass().getName() );
>             }
> 
>             // Close anyway
>             try {
>                 PrintWriter writer = response.getWriter();
>                 writer.close();
>             } catch (IllegalStateException e) {
>                 try {
>                     ServletOutputStream stream = 
> response.getOutputStream();
>                     stream.close();
>                 } catch (IllegalStateException f) {
>                     ;
>                 } catch (IOException f) {
>                     ;
>                 }
>             } catch (IOException e) {
>                 ;
>             }
>         }
> 
> In the above code sample, response will be an instance of
> ResponseFacade, meaning it will be suspended instead of being flushed
> and closed right away.
> 
> Does anyone remember why the "response instanceof ResponseFacade"
> check is there? I would have expected the "else" case to always be
> executed.
> 

Without ever actually having looked at ResponseFacade, I'd always assumed
that ResponseFacade.finish called Response.finishResponse.  And I would have
been wrong ;-).  This would have done the commit/send/close properly.

I don't have time right now to dig through the SVN logs to see why it's this
way, but suspended doesn't really look good enough to satisfy the spec.

> Any hints appreciated.
> 
> Thanks,
> 
> 
> Jan
> 
> 
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> 
> 
> 



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