Jsp生成页面验证码的方法

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生成随机验证码图片的Jsp页面

image.jsp------------------------------生成随机验证码图片的Jsp页面
代码如下：

<%@ page contentType="image/jpeg" import="java.awt.*, java.awt.image.*,java.util.*,javax.imageio.*" %> <%! Color getRandColor(int fc,int bc) { Random random = new Random(); if(fc>255) fc=255; if(bc>255) bc=255; int r=fc+random.nextInt(bc-fc); int g=fc+random.nextInt(bc-fc); int b=fc+random.nextInt(bc-fc); return new Color(r,g,b); } %> <% out.clear();//这句针对resin服务器，如果是tomacat可以不要这句 response.setHeader("Pragma","No-cache"); response.setHeader("Cache-Control","no-cache"); response.setDateHeader("Expires", 0); int width=60, height=20; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics(); Random random = new Random(); g.setColor(getRandColor(200,250)); g.fillRect(0, 0, width, height); g.setFont(new Font("Times New Roman",Font.PLAIN,18)); g.setColor(getRandColor(160,200)); for (int i=0;i<155;i++) { int x = random.nextInt(width); int y = random.nextInt(height); int xl = random.nextInt(12); int yl = random.nextInt(12); g.drawLine(x,y,x+xl,y+yl); } String sRand=""; for (int i=0;i<4;i++){ String rand=String.valueOf(random.nextInt(10)); sRand+=rand; g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110))); g.drawString(rand,13*i+6,16); } // 将认证码存入SESSION session.setAttribute("rand",sRand); g.dispose(); ImageIO.write(image, "JPEG", response.getOutputStream()); %>

logic.jsp--------------------------------登陆页面，在这里提供输入验证码然后提交并验证
代码如下：

<%@ page contentType="text/html;charset=gbk" %> <%@ page language="java" import="java.sql.*" errorPage="" %> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"> <title>用户登录</title> <script language="javascript"> function loadimage(){ document.getElementById("randImage").src = "image.jsp?"+Math.random(); } </script> </head> <body> <table width="256" border="0" cellpadding="0" cellspacing="0"> <!--DWLayoutTable--> <form action="validate.jsp" method="post" name="loginForm"> <tr> <td width="118" height="22" valign="middle" align="center"><input type="text" name="rand" size="15"></td> <td width="138" valign="middle" align="center"><img alt="code..." name="randImage" id="randImage" src="image.jsp" width="60" height="20" border="1" align="absmiddle"></td> </tr> <tr> <td height="36" colspan="2" align="center" valign="middle"><a href="javascript:loadimage();"><font class=pt95>看不清点我</font></a></td> </tr> <tr> <td height="36" colspan="2" align="center" valign="middle"><input type="submit" name="login" value="提交"></td> </tr> </form> </table> </body> </html>

validate.jsp--------------------------用来验证输入的验证码是否正确
代码如下：

<%@ page contentType="text/html; charset=gb2312" language="java" import="java.sql.*" errorPage="" %> <% String rand = (String)session.getAttribute("rand"); String input = request.getParameter("rand"); if(rand.equals(input)){ out.print("<script>alert('验证通过！');</script>"); } else{ out.print("<script>alert('请输入正确的验证码！');location.href='login.jsp';</script>"); } %>

以上三个JSP页面放在和WEB-INF同级目录下，如果你放在不同的文件夹下，那么里面相关页面的路径自己稍作更改就可以了。
友情提示：Tomcat5以下版本会出现异常。

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