jquery实现无刷新验证码的简单实例

import java.awt.Color;  import java.awt.Font;  import java.awt.Graphics2D;  import java.awt.image.BufferedImage;  import java.util.Random;    import javax.imageio.ImageIO;  import javax.servlet.ServletException;  import javax.servlet.ServletOutputStream;  import javax.servlet.http.HttpServlet;  import javax.servlet.http.HttpServletRequest;  import javax.servlet.http.HttpServletResponse;  import javax.servlet.http.HttpSession;    public class VerifyCodeServlet extends HttpServlet {      // 验证码图片的宽度。    private int width = 60;      // 验证码图片的高度。    private int height = 20;      // 验证码字符个数    private int codeCount = 4;      private int x = 0;      // 字体高度    private int fontHeight;      private int codeY;      char[] codeSequence = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',        'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',        'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };      /**     * 初始化验证图片属性     */    public void init() throws ServletException {      // 从web.xml中获取初始信息      // 宽度      String strWidth = this.getInitParameter("width");      // 高度      String strHeight = this.getInitParameter("height");      // 字符个数      String strCodeCount = this.getInitParameter("codeCount");        // 将配置的信息转换成数值      try {        if (strWidth != null && strWidth.length() != 0) {          width = Integer.parseInt(strWidth);        }        if (strHeight != null && strHeight.length() != 0) {          height = Integer.parseInt(strHeight);        }        if (strCodeCount != null && strCodeCount.length() != 0) {          codeCount = Integer.parseInt(strCodeCount);        }      } catch (NumberFormatException e) {      }        x = width / (codeCount + 1);      fontHeight = height - 2;      codeY = height - 4;      }      protected void service(HttpServletRequest req, HttpServletResponse resp)        throws ServletException, java.io.IOException {        // 定义图像buffer      BufferedImage buffImg = new BufferedImage(width, height,          BufferedImage.TYPE_INT_RGB);      Graphics2D g = buffImg.createGraphics();        // 创建一个随机数生成器类      Random random = new Random();        // 将图像填充为白色      g.setColor(Color.WHITE);      g.fillRect(0, 0, width, height);        // 创建字体，字体的大小应该根据图片的高度来定。      Font font = new Font("Fixedsys", Font.PLAIN, fontHeight);      // 设置字体。      g.setFont(font);        // 画边框。      g.setColor(Color.BLACK);      g.drawRect(0, 0, width - 1, height - 1);        // 随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。      g.setColor(Color.BLACK);      for (int i = 0; i < 160; i++) {        int x = random.nextInt(width);        int y = random.nextInt(height);        int xl = random.nextInt(12);        int yl = random.nextInt(12);        g.drawLine(x, y, x + xl, y + yl);      }        // randomCode用于保存随机产生的验证码，以便用户登录后进行验证。      StringBuffer randomCode = new StringBuffer();      int red = 0, green = 0, blue = 0;        // 随机产生codeCount数字的验证码。      for (int i = 0; i < codeCount; i++) {        // 得到随机产生的验证码数字。        String strRand = String.valueOf(codeSequence[random.nextInt(36)]);        // 产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同。        red = random.nextInt(255);        green = random.nextInt(255);        blue = random.nextInt(255);          // 用随机产生的颜色将验证码绘制到图像中。        g.setColor(new Color(red, green, blue));        g.drawString(strRand, (i + 1) * x, codeY);          // 将产生的四个随机数组合在一起。        randomCode.append(strRand);      }      // 将四位数字的验证码保存到Session中。      HttpSession session = req.getSession();      session.setAttribute("validateCode", randomCode.toString());        // 禁止图像缓存。      resp.setHeader("Pragma", "no-cache");      resp.setHeader("Cache-Control", "no-cache");      resp.setDateHeader("Expires", 0);        resp.setContentType("image/jpeg");        // 将图像输出到Servlet输出流中。      ServletOutputStream sos = resp.getOutputStream();      ImageIO.write(buffImg, "jpeg", sos);      sos.close();    }    } import java.awt.Color;import java.awt.Font;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class VerifyCodeServlet extends HttpServlet { // 验证码图片的宽度。 private int width = 60; // 验证码图片的高度。 private int height = 20; // 验证码字符个数 private int codeCount = 4; private int x = 0; // 字体高度 private int fontHeight; private int codeY; char[] codeSequence = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',  'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',  'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' }; /** * 初始化验证图片属性 */ public void init() throws ServletException { // 从web.xml中获取初始信息 // 宽度 String strWidth = this.getInitParameter("width"); // 高度 String strHeight = this.getInitParameter("height"); // 字符个数 String strCodeCount = this.getInitParameter("codeCount"); // 将配置的信息转换成数值 try {  if (strWidth != null && strWidth.length() != 0) {  width = Integer.parseInt(strWidth);  }  if (strHeight != null && strHeight.length() != 0) {  height = Integer.parseInt(strHeight);  }  if (strCodeCount != null && strCodeCount.length() != 0) {  codeCount = Integer.parseInt(strCodeCount);  } } catch (NumberFormatException e) { } x = width / (codeCount + 1); fontHeight = height - 2; codeY = height - 4; } protected void service(HttpServletRequest req, HttpServletResponse resp)  throws ServletException, java.io.IOException { // 定义图像buffer BufferedImage buffImg = new BufferedImage(width, height,  BufferedImage.TYPE_INT_RGB); Graphics2D g = buffImg.createGraphics(); // 创建一个随机数生成器类 Random random = new Random(); // 将图像填充为白色 g.setColor(Color.WHITE); g.fillRect(0, 0, width, height); // 创建字体，字体的大小应该根据图片的高度来定。 Font font = new Font("Fixedsys", Font.PLAIN, fontHeight); // 设置字体。 g.setFont(font); // 画边框。 g.setColor(Color.BLACK); g.drawRect(0, 0, width - 1, height - 1); // 随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。 g.setColor(Color.BLACK); for (int i = 0; i < 160; i++) {  int x = random.nextInt(width);  int y = random.nextInt(height);  int xl = random.nextInt(12);  int yl = random.nextInt(12);  g.drawLine(x, y, x + xl, y + yl); } // randomCode用于保存随机产生的验证码，以便用户登录后进行验证。 StringBuffer randomCode = new StringBuffer(); int red = 0, green = 0, blue = 0; // 随机产生codeCount数字的验证码。 for (int i = 0; i < codeCount; i++) {  // 得到随机产生的验证码数字。  String strRand = String.valueOf(codeSequence[random.nextInt(36)]);  // 产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同。  red = random.nextInt(255);  green = random.nextInt(255);  blue = random.nextInt(255);  // 用随机产生的颜色将验证码绘制到图像中。  g.setColor(new Color(red, green, blue));  g.drawString(strRand, (i + 1) * x, codeY);  // 将产生的四个随机数组合在一起。  randomCode.append(strRand); } // 将四位数字的验证码保存到Session中。 HttpSession session = req.getSession(); session.setAttribute("validateCode", randomCode.toString()); // 禁止图像缓存。 resp.setHeader("Pragma", "no-cache"); resp.setHeader("Cache-Control", "no-cache"); resp.setDateHeader("Expires", 0); resp.setContentType("image/jpeg"); // 将图像输出到Servlet输出流中。 ServletOutputStream sos = resp.getOutputStream(); ImageIO.write(buffImg, "jpeg", sos); sos.close(); }}

import java.io.IOException;  import java.io.PrintWriter;    import javax.servlet.ServletException;  import javax.servlet.http.HttpServlet;  import javax.servlet.http.HttpServletRequest;  import javax.servlet.http.HttpServletResponse;    public class ResultServlet extends HttpServlet {      /**     * The doGet method of the servlet. <br>     *     * This method is called when a form has its tag value method equals to get.     *     * @param request the request send by the client to the server     * @param response the response send by the server to the client     * @throws ServletException if an error occurred     * @throws IOException if an error occurred     */    public void doGet(HttpServletRequest request, HttpServletResponse response)        throws ServletException, IOException {        doPost(request, response);    }      /**     * The doPost method of the servlet. <br>     *     * This method is called when a form has its tag value method equals to post.     *     * @param request the request send by the client to the server     * @param response the response send by the server to the client     * @throws ServletException if an error occurred     * @throws IOException if an error occurred     */    public void doPost(HttpServletRequest request, HttpServletResponse response)        throws ServletException, IOException {        response.setContentType("text/html;charset=utf-8");      String validateC = (String) request.getSession().getAttribute("validateCode");      String veryCode = request.getParameter("c");      PrintWriter out = response.getWriter();      if(veryCode==null||"".equals(veryCode)){        out.println("验证码为空");      }else{        if(validateC.equals(veryCode)){          out.println("验证码正确");        }else{          out.println("验证码错误");        }      }      out.flush();      out.close();    }    } import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class ResultServlet extends HttpServlet { /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. *  * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response)  throws ServletException, IOException { doPost(request, response); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. *  * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doPost(HttpServletRequest request, HttpServletResponse response)  throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); String validateC = (String) request.getSession().getAttribute("validateCode"); String veryCode = request.getParameter("c"); PrintWriter out = response.getWriter(); if(veryCode==null||"".equals(veryCode)){  out.println("验证码为空"); }else{  if(validateC.equals(veryCode)){  out.println("验证码正确");  }else{  out.println("验证码错误");  } } out.flush(); out.close(); }}

function changeImg(){    var imgSrc = $("#imgObj");    var src = imgSrc.attr("src");    imgSrc.attr("src",chgUrl(src));  }  //时间戳  //为了使每次生成图片不一致，即不让浏览器读缓存，所以需要加上时间戳  function chgUrl(url){    var timestamp = (new Date()).valueOf();    url = url.substring(0,17);    if((url.indexOf("&")>=0)){      url = url + "×tamp=" + timestamp;    }else{      url = url + "?timestamp=" + timestamp;    }    return url;  }    function isRightCode(){    var code = $("#veryCode").attr("value");    code = "c=" + code;    $.ajax({      type:"POST",      url:"resultServlet",      data:code,      success:callback    });  }    function callback(data){    $("#info").html(data);  } function changeImg(){ var imgSrc = $("#imgObj"); var src = imgSrc.attr("src"); imgSrc.attr("src",chgUrl(src));}//时间戳//为了使每次生成图片不一致，即不让浏览器读缓存，所以需要加上时间戳function chgUrl(url){ var timestamp = (new Date()).valueOf(); url = url.substring(0,17); if((url.indexOf("&")>=0)){ url = url + "×tamp=" + timestamp; }else{ url = url + "?timestamp=" + timestamp; } return url;}function isRightCode(){ var code = $("#veryCode").attr("value"); code = "c=" + code; $.ajax({ type:"POST", url:"resultServlet", data:code, success:callback });}function callback(data){ $("#info").html(data);}

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%>  <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">  <html>    <head>      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">      <script type="text/javascript" src="js/verifyCode.js"></script>      <script type="text/javascript" src="js/jquery.js"></script>      <title>test verify code</title>    </head>    <body>      <input id="veryCode" name="veryCode" type="text"/>      <img id="imgObj" alt="" src="verifyCodeServlet"/>      <a href="#" onclick="changeImg()">换一张</a>      <input type="button" value="验证" onclick="isRightCode()"/>      <div id="info"></div>    </body>  </html>