我用eclipse在制作验证码时遇到的问题,棘手中

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setHeader("Cache-Control","no-cache"); 
response.setHeader("Pragma","no-cache");
response.setDateHeader ("Expires", 0);
response.setContentType("text/html");
BufferedImage img = new BufferedImage(80,30,BufferedImage.TYPE_INT_RGB);
Graphics grap = img.getGraphics();
grap.setColor(Color.GRAY);
grap.fillRect(0, 0,80,30);
ImageIO.write(img, "JPEG", response.getOutputStream());
}
------------------------------------以上是servlet中的内容------------
MyJsp.JSP页面中的内容:
<body>
    This is my JSP page. <br>
    <img src="servelt"/>
  </body>我想在servlet中画个矩形,并在MyJsp.jsp中显示出来,可是却无法显示.郁闷,我写的有错么?