java 制作验证码并进行验证实例详解

/** * 显示验证码图片 */public void showCheckCode(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {  // 调用业务逻辑  String checkCode = getCheckCode();  //将验证码字符放入session域对象中  req.getSession().setAttribute("checkCode", checkCode);  //图片宽  int width = 80;  //图片高  int height = 30;  //在内存中创建一个图片  BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);  //获取一个画笔  Graphics g = image.getGraphics();  //设置画笔颜色，用灰色做背景  g.setColor(Color.GRAY);  //向Image中填充灰色  g.fillRect(0,0,width,height);  Random r = new Random();  //设置3条干扰线  for (int i = 0; i < 3; i++) {    g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));    g.drawLine(r.nextInt(80), r.nextInt(30), r.nextInt(80), r.nextInt(80));  }  //设置验证码字符串的颜色  g.setColor(new Color(r.nextInt(255),r.nextInt(255),r.nextInt(255)));  //设置字符的大小  g.setFont(new Font("黑体",Font.BOLD,24));  //在图片中写入验证码字符串  g.drawString(checkCode,15,20);  //将Image对象以PNG格式输出给所有的客户端  ImageIO.write(image,"PNG",resp.getOutputStream());}/** * 获取4位验证码中的4位随机字符串 */public static String getCheckCode(){  //验证码中的字符由数字和大小写字母组成  String code = "0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM";  Random r = new Random();  StringBuffer sb = new StringBuffer();  for (int i = 0; i < 4; i++) {    sb.append(code.charAt(r.nextInt(code.length())));  }  return sb.toString();}

<script type="text/javascript">  function changeCodeImage(img){    img.src = "${pageContext.request.contextPath}/UserServlet?method=showCheckCode&time="+new Date().getTime();  }</script> <div class="form-group">  <label for="date" class="col-sm-2 control-label">验证码</label>  <div class="col-sm-3">   <input type="text" class="form-control" id="writeCode" onkeyup="checkCodeMethod(this.value)" >  </div>  <div class="col-sm-2">  <img src="${pageContext.request.contextPath}/UserServlet?method=showCheckCode" id="checkCodeImage"  </div>  <span id="checkCodeSpan"></span> </div>

/** * 验证验证码 */public void checkCode(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {  //获取从页面中接收到的验证码参数  String checkCode = req.getParameter("checkCode");  //从session域对象中获取验证码  String sessionCode = (String) req.getSession().getAttribute("checkCode");  //判断验证码是否相同  if (checkCode.equalsIgnoreCase(sessionCode)) {    resp.getWriter().print(true);  }else {    resp.getWriter().print(false);  }

<script type="text/javascript">  function changeCodeImage(img){    img.src = "${pageContext.request.contextPath}/UserServlet?method=showCheckCode&time="+new Date().getTime();  }  function checkCodeMethod(code){    $.get("${pageContext.request.contextPath}/UserServlet?method=checkCode",         { checkCode: code},         function(data){          if (data == 'true') {            document.getElementById("checkCodeSpan").innerHTML = "<font>验证码正确!</font>";          }else {            document.getElementById("checkCodeSpan").innerHTML = "<font>验证码错误!</font>";          }        }      );  }</script> <div class="form-group">  <label for="date" class="col-sm-2 control-label">验证码</label>  <div class="col-sm-3">   <input type="text" class="form-control" id="writeCode" onkeyup="checkCodeMethod(this.value)" >  </div>  <div class="col-sm-2">  <img src="${pageContext.request.contextPath}/UserServlet?method=showCheckCode" id="checkCodeImage"  </div>  <span id="checkCodeSpan"></span> </div>