点击验证码无刷新重新加载验证码图片
生成验证码图片的image.jsp：
<%@page contentType="image/jpeg;charset=utf-8"%>
<%@page import="java.util.*,java.awt.*,java.awt.image.*,javax.imageio.*" %>
<%@ page import="java.io.OutputStream" %>
<html>
<body>
<%!
Color getRandColor(int fc,int bc)
{
Random rd=new Random();
if(fc>255) fc=255;
if(bc>255) bc=255;
int red=fc+rd.nextInt(bc-fc);
int green=fc+rd.nextInt(bc-fc);
int blue=fc+rd.nextInt(bc-fc);
return new Color(red,green,blue);
}
%>
<%
Random r=new Random();
response.addHeader("Pragma","No-cache");
response.addHeader("Cache-Control","no-cache");
response.addDateHeader("expires",0);
int width=90;
int height=23;
BufferedImage pic=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
Graphics gc=pic.getGraphics();
gc.setColor(getRandColor(200,250));
gc.fillRect(0,0,width,height);
String[] rNum ={"0","1","2","3","4","5","6","7","8","9","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","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"};
int[] style = {Font.PLAIN,Font.BOLD,Font.ITALIC,Font.PLAIN+Font.BOLD,
Font.BOLD+Font.ITALIC,Font.PLAIN+Font.ITALIC,Font.PLAIN+Font.BOLD+Font.ITALIC};
gc.setColor(Color.WHITE);
gc.drawLine(0,30,90,10);
gc.setColor(getRandColor(160,200));
for (int i=0;i<50;i++)
{
int x = r.nextInt(width);
int y = r.nextInt(height);
int xl = r.nextInt(10);
int yl = r.nextInt(10);
gc.drawLine(x,y,x+xl,y+yl);
}
gc.setColor(getRandColor(60,150));
String rt = "";
for(int i=0;i<4;i++){
String temp = rNum[r.nextInt(62)];
rt = rt+temp;
gc.setFont(new Font("Times New Roman",style[r.nextInt(7)],15));
gc.drawString(temp,5+i*15+r.nextInt(10),10+r.nextInt(10));
}
gc.dispose();
session.setAttribute("randNum",rt);
OutputStream os=response.getOutputStream();
ImageIO.write(pic,"JPEG",os);
System.out.println("当前验证码为:"+session.getAttribute("randNum"));
os.flush();
os.close();
os=null;
response.flushBuffer();
out.clear();
out = pageContext.pushBody();
%>
</body>
</html>
实现无刷新重新加载步骤：
1.在需要使用验证码的网页文件头部加上js代码：
写道
<script language="JavaScript">
function reloadcode(){
var verify=document.getElementById('safecode');
verify.setAttribute('src','image.jsp?'+Math.random());
//这里必须加入随机数不然地址相同无法重新加载
}
</script>
function reloadcode(){
var verify=document.getElementById('safecode');
verify.setAttribute('src','image.jsp?'+Math.random());
//这里必须加入随机数不然地址相同无法重新加载
}
</script>
2.然后再验证码图片里面写onclick呼出上面的函数重新加载：
写道
<img src="image.jsp" id="safecode" border="0" onclick="reloadcode()"
style="cursor:hand;padding:2px 8px 0pt 3px;" />
style="cursor:hand;padding:2px 8px 0pt 3px;" />
3.两个文件在同一目录下，点击图片即可实现验证码重新加载
参考：http://zhidao.baidu.com/question/97875728.html
http://www.itwis.com/html/programme/javascript/20080416/1296.html