java中随机动态生成验证码
public class CheckCodeServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
//服务器通知浏览器不要缓存 response.setHeader("pragma","no-cache"); response.setHeader("cache-control","no-cache"); response.setHeader("expires","0"); //在内存中创建一个长80,宽30的图片,默认黑色背景 //参数一:长 //参数二:宽 //参数三:颜色 int width = 80; int height = 30; BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //获取画笔 Graphics g = image.getGraphics(); //设置画笔颜色为灰色 g.setColor(Color.GRAY); //填充图片 g.fillRect(0,0, width,height); //产生4个随机验证码,12Ey String checkCode = getCheckCode(); //将验证码放入HttpSession中 request.getSession().setAttribute("CHECKCODE_SERVER",checkCode); //设置画笔颜色为黄色 g.setColor(Color.YELLOW); //设置字体的小大 g.setFont(new Font("黑体",Font.BOLD,24)); //向图片上写入验证码 g.drawString(checkCode,15,25); //将内存中的图片输出到浏览器 //参数一:图片对象 //参数二:图片的格式,如PNG,JPG,GIF //参数三:图片输出到哪里去 ImageIO.write(image,"PNG",response.getOutputStream()); } /** * 产生4位随机字符串 */ private String getCheckCode() { String base = "0123456789ABCDEFGabcdefg"; int size = base.length(); Random r = new Random(); StringBuffer sb = new StringBuffer(); for(int i=1;i<=4;i++){ //产生0到size-1的随机值 int index = r.nextInt(size); //在base字符串中获取下标为index的字符 char c = base.charAt(index); //将c放入到StringBuffer中去 sb.append(c); } return sb.toString(); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doGet(request,response); }
}