jsp验证码 (通过单击验证码或超链接换验证码)

时间：2021-06-18 01:08:21
#code.jsp

<%@ page language="java"

    import="java.util.*"

    import="java.awt.*"

    import="java.awt.image.BufferedImage"

    import="javax.imageio.ImageIO"

    pageEncoding="UTF-8"

%>

<%

    response.setHeader("Cache-Control","no-cache");

    int width = 60;

    int height = 20;

    int length = 4;

    BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);

    //设置画笔

    Graphics g = image.getGraphics();

    //设定背景颜色

    g.setColor(new Color(200,200,200));

    g.fillRect(0, 0, width, height);

    //取随机产生的验证码（四位数字）

    String randStr = "";

    Random random = new Random();

    for (int i = 0; i < length; i++) {

        boolean b = random.nextBoolean();

        if (b) { // 字符串

            int choice = random.nextBoolean() ? 65 : 97; //取得65大写字母还是97小写字母

            randStr += (char) (choice + random.nextInt(26));// 取得大写字母

        } else { // 数字

            randStr += String.valueOf(random.nextInt(10));

        }

    }

    session.setAttribute("randStr", randStr);

    //将验证码显示到图像中

    g.setColor(Color.black);

    g.setFont(new Font("",Font.PLAIN,20));

    g.drawString(randStr,5,17);

    //随机产生100个干扰点，使图像不容易被其它程序探测

    for(int i=0; i<100; i++){

        int x = random.nextInt(width);

        int y = random.nextInt(height);

        g.drawOval(x,y,1,1);

    }

    //输出图像的到页面

    ImageIO.write(image,"JPEG",response.getOutputStream());

    out.clear();

    out = pageContext.pushBody();

%>

# loginForm.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<html>

    <body>

        welcome

        <br>

        <form name="loginForm" method="post" action="/Pro27/servlet/CheckCode">

            account:<input type="text" name="account"><br>

            password:<input type="password" name="password"><br>

            code:<input type="text" size="10" name="code">

            <img name="imgValidate" src="code.jsp" onClick="refresh()">

            <a href="javascript:refresh();">看不清,换一张 </a>

            <br>

            <input type="submit" value="login">

            <br>

            ${sessionScope.codeCheck }

            <%session.removeAttribute("codeCheck"); %>

        </form>

    </body>

    <script type="text/javascript" language="JavaScript">

        function refresh(){

            loginForm.imgValidate.src = "code.jsp?"+Math.random();//new Date(); 此处必须加上Math.random()或new Date()，否则无法刷新验证码

        }

    </script>

</html>

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