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>