本文實例講述了jsp+ajax實現的局部刷新較驗驗證碼(onblur事件觸發較驗)。分享給大家參考，如下：
前台顯示頁:
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>
產生圖片頁面
codevalidate .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());
%>
