I have seen this error message, when there is a call for
response.getWriter earlier on in the code.
Are you sure that you have not asked for the
Writer? ..response.getWriter()..?

blobstoreService.serve(blobKey, resp) will use
response.getOutputStream() and that can be tricky if you have already
asked for the Writer.
I don't think it matters if you have actually used the Writer or not.

Best regards
/Dick Larsson
www.Amantech.se
Stockholm/Sweden



On 20 Dec 2010, 10:04, Ahmed Shoeib <[email protected]>
wrote:
> hi all,
> i want to get image from blobstore using this code
>
> // Serve image from blob store
> BlobKey blobKey = new BlobKey(req.getParameter("apikey"));
> blobstoreService.serve(blobKey, resp);
>
> and facing this problem
>
> HTTP ERROR 500
>
> Problem accessing /api/news/serve. Reason:
>
>     WRITER
>
> Caused by:
>
> java.lang.IllegalStateException: WRITER
>         at org.mortbay.jetty.Response.getOutputStream(Response.java:594)
>         at
> javax.servlet.ServletResponseWrapper.getOutputStream(ServletResponseWrapper.java:
> 105)
>         at
> com.google.appengine.api.blobstore.dev.ServeBlobFilter.serveBlob(ServeBlobFilter.java:
> 169)
>         at
> com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:
> 62)
>         at org.mortbay.jetty.servlet.ServletHandler
> $CachedChain.doFilter(ServletHandler.java:1157)
>         at
> com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:
> 43)
>         at org.mortbay.jetty.servlet.ServletHandler
> $CachedChain.doFilter(ServletHandler.java:1157)
>         at
> com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:
> 122)
>         at org.mortbay.jetty.servlet.ServletHandler
> $CachedChain.doFilter(ServletHandler.java:1157)
>         at
> org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:
> 388)
>         at
> org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:
> 216)
>         at
> org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:
> 182)
>         at
> org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:
> 765)
>         at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:
> 418)
>         at
> com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:
> 70)
>         at
> org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:
> 152)
>         at com.google.appengine.tools.development.JettyContainerService
> $ApiProxyHandler.handle(JettyContainerService.java:349)
>         at
> org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:
> 152)
>         at org.mortbay.jetty.Server.handle(Server.java:326)
>         at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:
> 542)
>         at org.mortbay.jetty.HttpConnection
> $RequestHandler.headerComplete(HttpConnection.java:923)
>         at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
>         at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
>         at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
>         at
> org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:
> 409)
>         at org.mortbay.thread.QueuedThreadPool
> $PoolThread.run(QueuedThreadPool.java:582)

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