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jsp实现登录验证 JSP中图片验证是如何实现
JSP中图片验证是如何实现
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 sun image 不是java的标准包 需要另外下载 相关地址为:
random jsp (产生四位的随机字符 由 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 * sun image codec jpeg * java util *"%> <%@ page import="" contentType="text/; charset=gb "%> <% String chose=" abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
char display[]={ } ran[]={ } temp;
Random rand=new Random();
for(int i= ;i< ;i++) {
temp=chose charAt(rand nextInt(chose length()));
display[i* ]=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" ); int width= height= ; 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( width height); //设置字体颜色 g setColor(Color RED); g drawString(random ); g dispose(); ServletOutputStream outStream = response getOutputStream(); JPEGImageEncoder encoder =JPEGCodec createJPEGEncoder(outStream); encoder encode(image); outStream close(); %>
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/; charset=gb " 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( )</script>");
//response sendRedirect("img jsp"); } else { out println("<center>验证成功！</center>"); } } %> <> <head> <title>图片验证</title> <meta equiv="Content Type" content="text/; charset=gb "> </head>
<body> <form action="img jsp" method="post"> <table> <tr> <td> <input type=text name=num size= > </td> <td> <img src=random jsp> </td> </tr> </table> <input type=submit value="OK"> </form> </body> </>
lishixinzhi/Article/program/Java/JSP/201311/19860
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