JSP中图片验证的实现

2024-09-05 00:20:18

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来源：转载

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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>