下面小编就为大家带来一篇jquery实现无刷新验证码的简单实例。小编觉得挺不错的，现在分享给大家，也给大家做个参考。

1. 思路:

页面上的验证码图片是servlet,采用jquery实现异步校验信息

2. 所用到的文件

VerifyCodeServlet.java   --用于生成图片的servlet

ResultServlet.java  --用于校验验证码正确性的servlet

verifyCode.js  --校验的js文件

jquery.js  --jquery包里的源文件

verifyCode.jsp  --页面

3. 代码

VerifyCodeServlet.java

Java代码

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();

 }

}

ResultServlet.java

Java代码 

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();

 }

}

verifyCode.js

Js代码

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);

}

verifyCode.jsp

Html代码

<%@ 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> 

以上这篇jquery实现无刷新验证码的简单实例就是小编分享给大家的全部内容了，希望能给大家一个参考