图片验证码

//用SERVLET画出一个验证图片
public class imageValidate extends HttpServlet {
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setContentType("image/jpeg");
		response.setHeader("Cache-Control","public");
		response.setHeader("Cache-Control","max-age=600");
		int width=60, height=20;
	    BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
	    //获取图形上下文
        Graphics g = bufferedImage.getGraphics();
        
        //生成随机类
        Random random = new Random();

        // 画背景
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, width, height);
        
        //画边框
        g.setColor(Color.BLACK);
        g.drawRect(0,0,width-1,height-1);

        //设定字体
        g.setFont(new Font("Times New Roman",Font.PLAIN,18));

        // 取随机产生的认证码(4位数字)
        StringBuffer sRand = new StringBuffer();
        for (int i=0;i<4;i++){
            String rand=String.valueOf(random.nextInt(10));
            sRand.append(rand);
            //将认证码显示到图象中
            g.setColor(new Color(random.nextInt(225),random.nextInt(225),random.nextInt(225)));
            g.drawString(rand,13*i+6,16);
        }
        g.dispose();

        request.getSession(true).setAttribute("checknum", sRand.toString());
        
        ServletOutputStream responseOutputStream =response.getOutputStream();
        // 输出图象到页面
        ImageIO.write(bufferedImage, "JPEG", responseOutputStream);

        //以下关闭输入流！
        responseOutputStream.flush();
        responseOutputStream.close();
		
	}

//在JSP页面中可以直接引用上述servlet产生的随机码
<td>验证码：</td>
<td><input type="text" name="checkNum" style="width:200px"><img src="/shoppingcart/servlet/imageValidate"></td>