servlet向浏览器输出验证码图片

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servlet向浏览器输出验证码图片,注册页面的<img> 标签的src属性只需要指向该servlet即可

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//通知浏览器不要缓存图片response.setHeader("Expires", "-1");response.setHeader("Cache-Control", "no-cache");response.setHeader("Pragma", "no-cache");//通知浏览器以图片方式打开response.setHeader("Content-type", "image/jpeg");//在内存中创建一张图片BufferedImage image = new BufferedImage(100, 20, BufferedImage.TYPE_INT_RGB);//得到图片Graphics2D  g = (Graphics2D) image.getGraphics();

<span style="white-space:pre"></span>//设置背景色g.setColor(Color.WHITE);g.fillRect(0, 0, 100, 20);//向图片上写数据g.setColor(Color.GRAY);g.setFont(new Font(null,Font.BOLD,20));g.drawString(makeNum(), 0, 20);//写到浏览器ImageIO.write(image, "jpg", response.getOutputStream());}private String makeNum() {Random r = new Random();String num = r.nextInt(9999) + "";for (int i = 0; i < 4 - num.length(); i++){num += r.nextInt(9) ;}return num;}

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