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RE: Having problems with stored PrintWriter.

derrick robertson

2003-12-16

Replies:

Im trying to create a servlet that is able to push back to the browser rather than just operate a a pull mechanism.

To create this, there is a piece of javascript embedded within the html outputted to the browser, so when additional javascript code is written in at a later stage calling that function, that user can be notified of events he is registered to.

Perhaps not the way servlets were made to work but anyway!
Unless you are able to come up with a better solution?

How do i stop the response from ending then? I have left the html open at the end so no /html code and I have not closed the output to the browser.

 -----Original Message-----
 From: Ben Souther [mailto:bsouther@(protected)]
 Sent: Tue 16/12/2003 15:32
 To: Tomcat Users List
 Cc:
 Subject: Re: Having problems with stored PrintWriter.
 
 

 > I am trying to store users PrintWriter and use them again at a later date
 Just out of curiosity, why?
 
 
 
 
 On Tuesday 16 December 2003 10:12 am, derrick.robertson@(protected):
 > Im having a problem with PrintWriter in a servlet.
 >
 > I am trying to store users PrintWriter and use them again at a later date
 > to output javascript commands to the browsers at a later date. it store as
 > a coyotewriter - org.apache.coyote.tomcat5.CoyoteWriter@(protected)
 >
 > To do this they are dumped in a hashtable. But they dont seem to work when
 > i try to write output with them? Is there any way around this??
 >
 > this is the error I get but only when i include the flush() line.
 >
 > If anybody can help it would be most appreciated
 >
 > To write out to users browser - retrieves from hashtable
 > --------------------------------------------
 > System.out.println("Is this even working: Receivedevent!!!!!!!
 > "+useroutputstream); PrintWriter usersout =
 > (PrintWriter)useroutputstream.get("derrick"); usersout.println("Testing
 > received event status"+receivedevent);
 > usersout.print("<script type=\"text/javascript\">");
 > usersout.print("receivedEvent('your dinner is ready');");
 > usersout.print("</script>");
 > //extraline
 > usersout.flush(); -----> Exception:
 > lbp.LBPServlet.doGet(LBPServlet.java:98)
 >
 > I dont know if this is also part of the problem but if i use the .flush(),
 > it seems to start throwing exceptions.
 >
 > java.lang.NullPointerException
 > org.apache.coyote.http11.InternalOutputBuffer.commit(InternalOutputBuffer.j
 >ava:547)
 > org.apache.coyote.http11.Http11Processor.action (Http11Processor.java:735)
 > org.apache.coyote.Response.action (Response.java:223)
 > org.apache.coyote.http11.InternalOutputBuffer.doWrite(InternalOutputBuffer.
 >java:518) org.apache.coyote.Response.doWrite (Response.java:532)
 > org.apache.coyote.tomcat5.OutputBuffer.realWriteBytes (OutputBuffer.java:392
 >) org.apache.tomcat.util.buf.ByteChunk.flushBuffer (ByteChunk.java:439)
 > org.apache.coyote.tomcat5.OutputBuffer.flush (OutputBuffer.java:350)
 > org.apache.coyote.tomcat5.CoyoteWriter.flush (CoyoteWriter.java:119)
 > lbp.LBPServlet.doGet(LBPServlet.java:98)
 > javax.servlet.http.HttpServlet.service (HttpServlet.java:743)
 > javax.servlet.http.HttpServlet.service (HttpServlet.java:856)
 > org.apache.catalina.servlets.InvokerServlet.serveRequest(InvokerServlet.jav
 >a:466)
 > org.apache.catalina.servlets.InvokerServlet.doGet (InvokerServlet.java:180)
 > javax.servlet.http.HttpServlet.service (HttpServlet.java:743)
 > javax.servlet.http.HttpServlet.service (HttpServlet.java:856)
 > filters.ExampleFilter.doFilter(ExampleFilter.java:149)
 > filters.ExampleFilter.doFilter(ExampleFilter.java:149)
 
 --
 Ben Souther
 F.W. Davison & Company, Inc.
 
 
 
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