JSP中圖片驗證是如何?

最後更新：2017-02-28 來源：互聯網

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圖片驗證在有關註冊和發表留言經常用到.我在此用jsp寫了個.供大家參考. 其中 com.sun.image 不是java的標準包.需要另外下載.相關地址為: http://java.sun.com/products/java-media/jai/

1. random.jsp (產生四位的隨機字元,由0-9,a-z,A-Z構成.並把最終字串放到session中儲存以讓後續頁面驗證真偽)

代碼如下:

<%@ 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();
        //以下填充背景顏色
        g.setColor(Color.GREEN);
        g.fillRect(0, 0, width, height);
       //設定字型顏色
        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 (顯示驗證圖片.由於本程式簡單讓驗證程式也一併放在了一起)

代碼如下:

<%@ 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('驗證碼錯誤！請重試。')</script>");

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

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

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