JSP中图片验证的实现

2008-02-23 07:50:48来源：互联网阅读 ()

图片验证在有关注册和发表留言经常用到.我在此用jsp写了个.供大家参考. 其中 com.sun.image 不是java的标准包.需要另外下载.相关地址为:

http://java.sun.com/products/java-media/jai/

1. random.jsp (产生四位的随机字符,由0-9,a-z,A-Z构成.并把最终字符串放到session中保存以让后续页面验证真伪)

代码如下:

<%@ page autoFlush="false" import="java.util.*,java.awt.*,java.awt.image.*,com.sun.image.codec.jpeg.*,java.util.*"%>
<%@ page import="" contentType="text/html; charset=gb2312"%>
<%
String chose="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

char display[]={'0',' ','0',' ','0',' ','0'},ran[]={'0','0','0','0'},temp;

Random rand=new Random();

for(int i=0;i<4;i )
{

temp=chose.charAt(rand.nextInt(chose.length()));

display[i*2]=temp;

ran[i]=temp;
}

String random=String.valueOf(display);

session.setAttribute("random",String.valueOf(ran));
%>
<%

out.clear();
response.setContentType("image/jpeg");
response.addHeader("pragma","NO-cache");
response.addHeader("Cache-Control","no-cache");
response.addDateHeader("Expries",0);
int width=47, height=15;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
//以下填充背景颜色
g.setColor(Color.GREEN);
g.fillRect(0, 0, width, height);
//设置字体颜色
g.setColor(Color.RED);
g.drawString(random,3,10);
g.dispose();
ServletOutputStream outStream = response.getOutputStream();
JPEGImageEncoder encoder =JPEGCodec.createJPEGEncoder(outStream);
encoder.encode(image);
outStream.close();
%>

2. img.jsp (显示验证图片.由于本程序简单让验证程序也一并放在了一起)

代码如下:

<%@ page contentType="text/html; charset=gb2312" language="java"%>
<%
String num=request.getParameter("num");
String random=(String)session.getAttribute("random");

if(num!=null&&random!=null)
{
if(!num.equals(random))
{
out.println("<script>alert('验证码错误！请重试。')</script>");

out.println("<script>history.go(-1)</script>");

//response.sendRedirect("img.jsp");
}
else
{
out.println("<center>验证成功！</center>");
}
}
%>
<html>
<head>
<title>图片验证</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head>