JSP : getOutputStream() has already been called for this response

Question

I am using this code to download file from FTP. I am getting exception in tomcat log as below, i am able to perform my task but my log size increases a lot.

Code:

   if (file.exists())
   {
       if (file.canRead())
       {
          // IE6 & SSL PDF Bug
          // http://forums.sun.com/thread.jspa?threadID=526451&start=15&tstart=0

           mimeType = new javax.activation.MimetypesFileTypeMap().getContentType(file);
           response.setHeader("Cache-Control","private");
           response.setHeader("Pragma","expires");
           response.setHeader("Content-Disposition", "inline; filename=\"" + org.apache.commons.io.FilenameUtils.getName(file.getAbsolutePath()) + "\"");
           response.setContentType(mimeType);
           response.setContentLength((new Long(file.length())).intValue());
           byte[] buffer = new byte[(int)org.apache.commons.io.FileUtils.ONE_KB * 64];
           output=response.getOutputStream();
           bos = new java.io.BufferedOutputStream(output, buffer.length);
           bis = new java.io.BufferedInputStream(new java.io.FileInputStream(file));
           while (bis.read(buffer) != -1)
           {
               bos.write(buffer);
           }
           bos.flush();
       }
       else{System.out.println("Cannot read from file");}
   }
   else{System.out.println("File dosen't exist");}

Error Message

    Jan 18, 2014 6:11:31 AM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet jsp threw exception
 java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:611)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:188)
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:118)
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:77)

I saw post regarding adding code to servlet, also closing the output stream but none of that worked. Please assist.

Answer 1

you shouldn't do this in JSP but you should use a Servlet (even if a jsp page is far more pratical)

however if you still want to use a jsp page, use this directive:

<%@page language="java" trimDirectiveWhitespaces="true"%>

apart from question, since you are using commons-io:

if (file.exists())
{
    if (file.canRead())
    {
       // IE6 & SSL PDF Bug
       // http://forums.sun.com/thread.jspa?threadID=526451&start=15&tstart=0

        mimeType = new javax.activation.MimetypesFileTypeMap().getContentType(file);
        response.setHeader("Cache-Control","private");
        response.setHeader("Pragma","expires");
        response.setHeader("Content-Disposition", "inline; filename=\"" + org.apache.commons.io.FilenameUtils.getName(file.getAbsolutePath()) + "\"");
        response.setContentType(mimeType);
        response.setHeader("Content-Length", String.valueOf(file.length()));

        OutputStream output = response.getOutputStream();
        FileUtils.copyFile(file, output);
        output.close();
    }
    else{System.out.println("Cannot read from file");}
}
else{System.out.println("File dosen't exist");}

Answer 2

Use a Servlet to send binary data in a response, not a JSP page. JSP pages send text output, and will invoke the getWriter method in order to send the buffered output from the JSP page.

See also this question.