jsp+ajax局部刷新校验验证码，onblur触发校验

前台显示页面:

welcome.jsp

<%@ page language="java" contentType="text/html; 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">
<title>修改个人信息</title>
<script>


function createXMLHttpRequest() {
    //表示当前浏览器不是ie,如ns,firefox
    if(window.XMLHttpRequest) {
        xmlHttp = new XMLHttpRequest();
    } else if (window.ActiveXObject) {
        xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
}
function validate(field) {
 var div=document.getElementById("divbid");
// var reg=/[^A-Za-z0-9_]{7,10}/g;
    if (field.value.length != 0) {


       //创建XMLHttpRequest
        createXMLHttpRequest();
        var url = "codevalidate.jsp?authcode=" + field.value + "×tamp=" + new Date().getTime();//加时间戳防止缓存重复
        xmlHttp.open("GET", url, true);
        //方法地址，处理完成后自动调用，回调
        xmlHttp.onreadystatechange=function() { //匿名函数
            if(xmlHttp.readyState == 4) { //Ajax引擎初始化成功
                if (xmlHttp.status == 200) { //http协议成功
                    document.getElementById("divbid").innerHTML =xmlHttp.responseText;
                }else {
                    alert("请求失败，错误码=" + xmlHttp.status);
                }
            }
        };
        //将参数发送到Ajax引擎
        xmlHttp.send(null);




    }else {

          div.innerHTML="<div  class=\"wrong\">验证码不能为空</div>"
    }
}

function reloadImage(imgurl){

    var getimagecode=document.getElementById("codeimg");
    getimagecode.src= imgurl + "?id=" + Math.random();
      var code=<%=session.getAttribute("code")%>;
      alert(code)
}
</script>

</head>
<body>

<form action="authcode.jsp" method="post" name="loginform">

      输入验证码：<input type="text" name="authcode" id="authcode" maxlength="4" size="10" onblur="validate(this)" ><span id="divbid"></span>
      <img id="codeimg" name="codeimg" border=0 src="authcode.jsp">
      <a href="javascript:reloadImage('authcode.jsp')">看不清</a><br/>

  </form> 

  <script language="javascript" type="text/javascript">
      function reloadImage(imgurl){

          var getimagecode=document.getElementById("codeimg");
          getimagecode.src= imgurl + "?id=" + Math.random();
          var code=<%=session.getAttribute("code")%>;
          alert(code)
      }
  </script>
  </body>
  </html>

产生图片页面

authcode.jsp

<%@ page contentType="image/JPEG"  
    import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"  
    pageEncoding="GBK"%>
<%!Color getRandColor(int fc, int bc) {//给定范围获得随机颜色   
        Random random = new Random();   
        if (fc > 255)   
            fc = 255;   
        if (bc > 255)   
            bc = 255;   
        int r = fc + random.nextInt(bc - fc);   
        int g = fc + random.nextInt(bc - fc);   
        int b = fc + random.nextInt(bc - fc);   
        return new Color(r, g, b);   
    }%>  
<%   
    //设置页面不缓存   
    response.setHeader("Pragma", "No-cache");   
    response.setHeader("Cache-Control", "no-cache");   
    response.setDateHeader("Expires", 0);   

    // 在内存中创建图象   
    int width = 60, height = 20;   
    BufferedImage image = new BufferedImage(width, height,   
            BufferedImage.TYPE_INT_RGB);   

    // 获取图形上下文   
    Graphics g = image.getGraphics();   

    //生成随机类   
    Random random = new Random();   

    // 设定背景色   
    g.setColor(getRandColor(200, 250));   
    g.fillRect(0, 0, width, height);   

    //设定字体   
    g.setFont(new Font("Times New Roman", Font.PLAIN, 18));   

    //画边框   
    //g.setColor(new Color());   
    //g.drawRect(0,0,width-1,height-1);   

    // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到   
    g.setColor(getRandColor(160, 200));   
    for (int i = 0; i < 100; 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);   
    }   

    // 取随机产生的认证码(4位数字)   
    String sRand = "";
    for (int i = 0; i < 4; i++) {   
        String rand = String.valueOf(random.nextInt(10));   
        sRand += rand;   
        // 将认证码显示到图象中   
        g.setColor(new Color(20 + random.nextInt(110), 20 + random   
        .nextInt(110), 20 + random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成   
        g.drawString(rand, 13 * i + 6, 16);   
        System.out.println(rand);
    }   

    // 将认证码存入SESSION   
    session.setAttribute("code", sRand);   

    // 图象生效   
    g.dispose();   

    // 输出图象到页面   
    ImageIO.write(image, "JPEG", response.getOutputStream());   
%>

ajax动态验证页面

codevalidate.jsp

<%@ page language="java" import="java.util.*,java.util.*,java.text.*,com.neusoft.xkxt.dao.*,com.neusoft.xkxt.bean.*,com.neusoft.xkxt.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%

   String authcode=request.getParameter("authcode");
   String code=(String)session.getAttribute("code");



   if(authcode.equals(code)){
   out.println("<div class='right'>√</div>");}

   else{
   out.println("<div class='wrong'>验证码不正确</div>");}

 %>