纯数字验证码

[img][/img]

后台：(code为验证码文本框用户输入，rand为session中图片数字)
String sss=request.getSession().getAttribute("rand").toString();//获取session中的验证码
//判断验证码，code为用户输入的验证码
if("".equals(this.getCode())||!sss.trim().equals(this.getCode()))
{
out
.print("<script>alert('验证码错误！');history.go(-1);</script>");
out.flush();
out.close();
}
*****************************
前台jsp:
<tr>
                <td height="40" class="fontbs">验证码：</td>
                <td>
                <input name="code" type="text" class="inputcode">
                </td>
                <td width="81" align="center">
                <a href="javascript:loadimage();" >
     <img alt="点击刷新"
        name="randImage" id="randImage"
        src="shouye/image.jsp"
        width="76"
        height="33"
        border="1"
       />
</a>
                </td>
              </tr>
js部分：
<script language="JavaScript">
      //刷新验证码
    function loadimage()
     {
           document.getElementById("randImage").src= "shouye/image.jsp?"+Math.random();
     }
</script>
************************************
验证码jsp:
image.jsp
********************
<%@ page contentType="image/jpeg" import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="UTF-8"%>
<%!
Color getRandColor(int fc,int bc)
{
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);
}
%>
<%
out.clear();//这句针对resin服务器，如果是tomcat可以不要这句
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
g.setFont(new Font("Times New Roman",Font.PLAIN,18));
g.setColor(getRandColor(160,200));
for (int i=0;i<155;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);
}
String sRand="";
for (int i=0;i<4;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
g.drawString(rand,13*i+6,16);
}
// 将认证码存入SESSION
session.setAttribute("rand",sRand);
g.dispose();
ImageIO.write(image, "JPEG", response.getOutputStream());
%>
*******************结束