JSP动态生成验证码并单击切换验证码

jopen 7年前

验证码生成jsp代码:

<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>  <%@ 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 = 70, 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("宋体", Font.PLAIN, 18));     //画边框   g.setColor(Color.black);   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);   }     char[] cs = new char[] { '1', '2', '3', '4', '5', '6', '7', '8',     '9', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'A',     'B', 'M' };     // 取随机产生的认证码(4位数字)   String sRand = "";   for (int i = 0; i < 4; i++) {    char c = cs[random.nextInt(cs.length)];    String rand = new Character(c).toString();    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); //这行代码使我们关注的重点   // 图象生效   g.dispose();     // 输出图象到页面   try {    ImageIO.write(image, "JPEG", response.getOutputStream());   } catch (Exception e) {    e.getMessage();   } finally {      //解决以调用错误    out.clear();    out = pageContext.pushBody();   }  %>
测试页面:
<body>   验证码:<img alt="" onclick="test();" src="image.jsp">    </body>        <script type="text/javascript">     function test(){    var image = document.getElementsByTagName("img")[0];    var myDate = new Date();    image.src = "image.jsp?time="+myDate.getTime();    alert(image.src);      }    </script>
测试效果:
204329_o47e_203585.png