表单
<form action="loginServlet" method="post"> 请输入验证码：<input type="text" name="code" /> <img src="getCodeServlet" /><br /> <button type="submit">提交</button> </form>
载入页面时，会自动请求getCodeServlet，获取图片（验证码）。
getCodeServlet，产生验证码
1 @WebServlet("/getCodeServlet") 2 public class GetCodeServlet extends HttpServlet { 3 //验证码的宽、高 4 private static int WIDTH=80; 5 private static int HEIGHT=25; 6 7 //绘制背景 8 private void drawBg(Graphics g){ 9 //rgb 10 g.setColor(new Color(128, 128, 128)); 11 //绘制矩形。x,y,wigth,height 12 g.fillRect(0,0,WIDTH,HEIGHT); 13 //随机绘制100个干扰点 14 Random random=new Random(); 15 for (int i=0;i<100;i++){ 16 //产生(0,1）上的小数，*WIDTH|HEIGHT，再取整也行 17 int x=random.nextInt(WIDTH); 18 int y=random.nextInt(HEIGHT); 19 g.drawOval(x,y,1,1); 20 21 //干扰点的颜色也可以随机，随机产生red，green，blue即可 22 //g.setColor(new Color(red,green,blue)); 23 } 24 } 25 26 27 //绘制验证码 28 private void drawCode(Graphics g,char[] code){ 29 g.setColor(Color.BLACK); 30 //字体、样式（多个时竖线分隔）、字号 31 g.setFont(new Font("serif",Font.ITALIC|Font.BOLD,18)); 32 //在不同位置绘制验证码字符，参数：要绘制的String、横、纵坐标。+""是为了char转String。 33 g.drawString(code[0]+"",1,17); 34 g.drawString(code[1]+"",16,15); 35 g.drawString(code[2]+"",31,18); 36 g.drawString(code[3]+"",46,16); 37 } 38 39 //随机产生4位验证码 40 private char[] getCode(){ 41 String chars="0123456789QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm"; 42 char[] code=new char[4]; 43 Random random=new Random(); 44 for (int i=0;i<4;i++){ 45 //[0,62) 46 int index= random.nextInt(62); 47 code[i]=chars.charAt(index); 48 } 49 return code; 50 } 51 52 53 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException { 54 HttpSession session = request.getSession(); 55 ServletOutputStream sos = response.getOutputStream(); 56 response.setContentType("image/jpeg"); 57 58 //设置浏览器不缓存此图片 59 response.setHeader("Pragma","No-cache"); 60 response.setHeader("Cache-Control","no-cache"); 61 response.setDateHeader("Expires",0); 62 63 //创建内存图片 64 BufferedImage bufferedImage = new BufferedImage(WIDTH, HEIGHT, TYPE_INT_RGB); 65 Graphics g= bufferedImage.getGraphics(); 66 char[] code=getCode(); 67 //将验证码放到session域中。session对象要在提交响应之前获得 68 session.setAttribute("code",new String(code)); 69 drawBg(g); 70 drawCode(g,code); 71 g.dispose(); 72 73 //将图片输出到浏览器 74 ByteArrayOutputStream baos = new ByteArrayOutputStream(); 75 ImageIO.write(bufferedImage,"JPEG",baos); 76 baos.writeTo(sos); 77 baos.close(); 78 sos.close(); 79 } 80 81 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException { 82 doPost(request,response); 83 } 84 }
loginServlet，处理表单
1 @WebServlet("/loginServlet") 2 public class LoginServlet extends HttpServlet { 3 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 4 response.setContentType("text/html;charset=utf-8"); 5 HttpSession session = request.getSession(); 6 String trueCode= (String) session.getAttribute("code"); 7 String code=request.getParameter("code"); 8 9 if (code.equals(trueCode)){ 10 response.getWriter().write("验证码正确"); 11 } 12 else { 13 response.getWriter().write("验证码错误"); 14 } 15 } 16 17 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 18 doPost(request,response); 19 } 20 }
上面的处理方式要区分验证码的大小写。
不区分大小写：
//先转换为全大写|全小写，再判断 trueCode=trueCode.toLowerCase();
code=code.toLowerCase(); //trueCode=trueCode.toUpperCase(); //code=trueCode.toUpperCase();
如果您觉得本文的内容对您的学习有所帮助：
关键字：
Session