JSP生成数字验证码

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JSP JavaScript HTML Cache

1.建立image.jsp代码如下
<%@ page contentType="image/jpeg"
   import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%!Color getRandColor(int fc, int bc) { //给定范围获得随机颜色
       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);
   }
%>
<%
   //设置页面不缓存
   response.setHeader("Pragma", "No-cache");
   response.setHeader("Cache-Control", "no-cache");
   response.setDateHeader("Expires", 0);

   //在内存中创建图象
   int width = 60, height = 20;
   BufferedImage image = new BufferedImage(width, height,
           BufferedImage.TYPE_INT_RGB);

   //获取图形上下文
   Graphics g = image.getGraphics();

   //生成随机类
   Random random = new Random();

   //设定背景色
   g.setColor(getRandColor(200, 250));
   g.fillRect(0, 0, width, height);

   //设定字体
   g.setFont(new Font("Comic Sans MS", Font.PLAIN, 20));

   //画边框
   //g.setColor(new   Color());
   //g.drawRect(0,0,width-1,height-1);

   //随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
   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);
   }

   //   取随机产生的认证码(4位数字)
   String sRand = "";
   for (int i = 0; i < 4; i++) {
       String rand = String.valueOf(random.nextInt(10));
       sRand += rand;
       //将认证码显示到图象中
       g.setColor(new Color(20 + random.nextInt(110), 20 + random
       .nextInt(110), 20 + random.nextInt(110)));
       //调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
       g.drawString(rand, 13 * i + 6, 16);
   }

   //将认证码存入SESSION
   session.setAttribute("rand", sRand);

   //图象生效
   g.dispose();

   //   输出图象到页面
   ImageIO.write(image, "JPEG", response.getOutputStream());
%>

2。建立验证页面Check.jsp如下：

<%@ page language="java" contentType="text/html; charset=GB2312"
   pageEncoding="GB2312"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GB2312">
<title>验证</title>
</head>
<body>
<%!
   String rand =null;
   String input = null;
%>
<%
   rand = (String) session.getAttribute("rand");
   input = request.getParameter("yanzhengma");
%>
验证码为：<%=rand%>
您的输入为：<%=input%>
<%if(rand.equals(input)){%>
   <font color=green>输入相同，认证成功！</font>
<%}else{%>
   <font color=red>输入不同，认证失败！</font>
<%}%>
</body>
</html>

3.建立登录页面index.jsp如下：
<%@ page language="java" contentType="text/html; charset=GB2312"
    pageEncoding="GB2312"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<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>
    <form action="Check.jsp" method="post" name="loginForm">
      <tr>
          <td width="118" height="22" valign="middle" align="center">
              <input type="text" name="yanzhengma" size="15">
          </td>
          <td width="138" valign="middle" align="center">
              <img alt="验证码" 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>
</body>
</html>

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