JSP中图片验证的实现

JSP中图片验证的实现

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("");
out.println("");
//response.sendRedirect("img.jsp");}else

{out.println("

验证成功！");

}}

%>