java.lang.IllegalStateException: STREAM
  at org.eclipse.jetty.server.Response.getWriter(Response.java:707)

java.lang.IllegalStateException: WRITER
  at org.eclipse.jetty.server.Response.getOutputStream(Response.java:681)

/**
 * Returns a {@link ServletOutputStream} suitable for writing binary 
 * data in the response. The servlet container does not encode the
 * binary data.  
 
 * <p> Calling flush() on the ServletOutputStream commits the response.
 
 * Either this method or {@link #getWriter} may 
 * be called to write the body, not both.
 *
 * @return				a {@link ServletOutputStream} for writing binary data	
 *
 * @exception IllegalStateException if the <code>getWriter</code> method
 * 					has been called on this response
 *
 * @exception IOException 		if an input or output exception occurred
 *
 * @see 				#getWriter
 *
 */

public ServletOutputStream getOutputStream() throws IOException;

/**
 * Returns a <code>PrintWriter</code> object that
 * can send character text to the client.
 * The <code>PrintWriter</code> uses the character
 * encoding returned by {@link #getCharacterEncoding}.
 * If the response's character encoding has not been
 * specified as described in <code>getCharacterEncoding</code>
 * (i.e., the method just returns the default value 
 * <code>ISO-8859-1</code>), <code>getWriter</code>
 * updates it to <code>ISO-8859-1</code>.
 * <p>Calling flush() on the <code>PrintWriter</code>
 * commits the response.
 * <p>Either this method or {@link #getOutputStream} may be called
 * to write the body, not both.
 *
 * 
 * @return 		a <code>PrintWriter</code> object that 
 *			can return character data to the client 
 *
 * @exception UnsupportedEncodingException
 *			if the character encoding returned
 *			by <code>getCharacterEncoding</code> cannot be used
 *
 * @exception IllegalStateException
 *			if the <code>getOutputStream</code>
 * 			method has already been called for this 
 *			response object
 *
 * @exception IOException
 *			if an input or output exception occurred
 *
 * @see 		#getOutputStream
 * @see 		#setCharacterEncoding
 *
 */

public PrintWriter getWriter() throws IOException;

public ServletOutputStream getOutputStream() throws IOException
{
    if (_outputState!=NONE && _outputState!=STREAM)
        throw new IllegalStateException("WRITER");

    ServletOutputStream out = _connection.getOutputStream();
    _outputState=STREAM;
    return out;
}

public PrintWriter getWriter() throws IOException
 {
     if (_outputState!=NONE && _outputState!=WRITER)
         throw new IllegalStateException("STREAM");

     /* if there is no writer yet */
     if (_writer==null)
     {
         /* get encoding from Content-Type header */
         String encoding = _characterEncoding;

         if (encoding==null)
         {
             /* implementation of educated defaults */
             if(_cachedMimeType != null)
                encoding = MimeTypes.getCharsetFromContentType(_cachedMimeType);

             if (encoding==null)
                 encoding = StringUtil.__ISO_8859_1;

             setCharacterEncoding(encoding);
         }

         /* construct Writer using correct encoding */
         _writer = _connection.getPrintWriter(encoding);
     }
     _outputState=WRITER;
     return _writer;
 }