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List:       tapestry-user
Subject:    Custom service to provide files from DB: getOutputStream() has already been called for this response
From:       Kaspar Fischer <fischerk () inf ! ethz ! ch>
Date:       2008-01-18 13:52:58
Message-ID: 08F3F30B-AE66-4361-A5AB-7F8E0C94628F () inf ! ethz ! ch
[Download RAW message or body]

Hi!

I have a custom service that downloads images/files from a DB:

   public void service(IRequestCycle cycle) throws IOException
   {
     // extract node-ref
     String nodeUID = cycle.getParameter("node");
     NodeRef nodeRef = new NodeRef(NODE_REF_PREFIX + nodeUID);

     try {
       // login to DB
       // ...
       content = ...;

       // get stream to content
       InputStream contentStream = content.getContent();
       response.setContentType(content.getContentMimeType());
       response.setContentLength(new Long(content.getContentSize 
()).intValue());
       ServletOutputStream out = response.getOutputStream();

       // transmit
       final int SIZE = 10 * 1024;
       byte[] buffer = new byte[SIZE];
       int i;
       while ((i = contentStream.read(buffer)) != -1)
         out.write(buffer, 0, i);
       contentStream.close();
       out.close();

     } catch (Exception e) {
       throw new ApplicationRuntimeException("Could not deliver file  
"+ nodeRef + ".", e);
     }
   }

When I heavily load files (clicking reload many times in fast  
succession), I get

ERROR http-80-Processor21 org.apache.catalina.core.ContainerBase. 
[Catalina].[localhost].[/kc].[kc] - Servlet.service() for servlet kc  
threw exception
java.lang.IllegalStateException: getOutputStream() has already been  
called for this response
         at org.apache.catalina.connector.Response.getWriter 
(Response.java:601)
         at org.apache.catalina.connector.ResponseFacade.getWriter 
(ResponseFacade.java:196)
         at org.apache.tapestry.web.ServletWebResponse.getPrintWriter 
(ServletWebResponse.java:116)
         at $WebResponse_1178d289d55.getPrintWriter 
($WebResponse_1178d289d55.java)
         at $WebResponse_1178d289ccb.getPrintWriter 
($WebResponse_1178d289ccb.java)
         at  
org.apache.tapestry.services.impl.DefaultResponseBuilder.renderResponse( 
DefaultResponseBuilder.java:140)
         at  
org.apache.tapestry.services.impl.ResponseRendererImpl.renderResponse 
(ResponseRendererImpl.java:33)
         at $ResponseRenderer_1178d289ce3.renderResponse 
($ResponseRenderer_1178d289ce3.java)
         at  
org.apache.tapestry.error.ExceptionPresenterImpl.presentException 
(ExceptionPresenterImpl.java:48)
         at $ExceptionPresenter_1178d289cd4.presentException 
($ExceptionPresenter_1178d289cd4.java)
         at $ExceptionPresenter_1178d289cd3.presentException 
($ExceptionPresenter_1178d289cd3.java)
         at  
org.apache.tapestry.engine.AbstractEngine.activateExceptionPage 
(AbstractEngine.java:117)
         at org.apache.tapestry.engine.AbstractEngine.service 
(AbstractEngine.java:269)
         at  
org.apache.tapestry.services.impl.InvokeEngineTerminator.service 
(InvokeEngineTerminator.java:54)
         at $WebRequestServicer_1178d289d2d.service 
($WebRequestServicer_1178d289d2d.java)
         at $WebRequestServicer_1178d289d29.service 
($WebRequestServicer_1178d289d29.java)
         at  
org.apache.tapestry.services.impl.WebRequestServicerPipelineBridge.servi 
ce(WebRequestServicerPipelineBridge.java:61)
         at $ServletRequestServicer_1178d289d0f.service 
($ServletRequestServicer_1178d289d0f.java)
         at org.apache.tapestry.request.DecodedRequestInjector.service 
(DecodedRequestInjector.java:55)
         at $ServletRequestServicerFilter_1178d289d0b.service 
($ServletRequestServicerFilter_1178d289d0b.java)
         at $ServletRequestServicer_1178d289d11.service 
($ServletRequestServicer_1178d289d11.java)
         at  
org.apache.tapestry.multipart.MultipartDecoderFilter.service 
(MultipartDecoderFilter.java:52)
         at $ServletRequestServicerFilter_1178d289d09.service 
($ServletRequestServicerFilter_1178d289d09.java)
         at $ServletRequestServicer_1178d289d11.service 
($ServletRequestServicer_1178d289d11.java)
         at  
org.apache.tapestry.services.impl.SetupRequestEncoding.service 
(SetupRequestEncoding.java:53)
         at $ServletRequestServicerFilter_1178d289d0d.service 
($ServletRequestServicerFilter_1178d289d0d.java)
         at $ServletRequestServicer_1178d289d11.service 
($ServletRequestServicer_1178d289d11.java)
         at $ServletRequestServicer_1178d289d03.service 
($ServletRequestServicer_1178d289d03.java)
         at org.apache.tapestry.ApplicationServlet.doService 
(ApplicationServlet.java:126)
         at org.apache.tapestry.ApplicationServlet.doGet 
(ApplicationServlet.java:103)
         at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)


Does anybody know what could be the reason for this? It does not  
occur when I
do one request after the other with pauses in between.

It seems to be something tapestry-specific as I am not calling  
getOutputStream() stream
twice! Or is my service() called twice? But why?

Many thanks in advance for any pointers!
Kaspar

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