验证码

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ page import="java.awt.*,java.awt.image.*,javax.imageio.*"%>
<jsp:directive.page import="java.io.OutputStream"/>
<jsp:directive.page import="com.sun.image.codec.jpeg.JPEGImageEncoder"/>
<jsp:directive.page import="com.sun.image.codec.jpeg.JPEGCodec"/>
<%
/*
使用方法：在需要显示验证码的html代码中使用
在需判断session的时候判断session.getAttribute("vcode")
*/try {
   int codeLength = 5;//验证码长度
   int mixTimes = 250;//模糊程度参数
   Color bgColor = getRandColor(200, 250);//背景颜色
   Color bfColor = new Color(0, 0, 0);//字体颜色
   boolean ifRandomColor = true;//单个字符是否颜色随机
   boolean ifMixColor = true;//模糊线是否颜色随机

   //设置页面不缓存
   response.setHeader("Pragma", "No-cache");
   response.setHeader("Cache-Control", "no-cache");
   response.setDateHeader("Expires", 0);
   response.setContentType("image/png");

   // 在内存中创建图象
   int width = 18 * codeLength + 6, height = 20;
   BufferedImage image = new BufferedImage(width, height,
   BufferedImage.TYPE_INT_RGB);
   // 获取图形上下文
   Graphics g = image.getGraphics();
   // 设定背景色
   g.setColor(bgColor);
   g.fillRect(0, 0, width, height);
   //设定字体
   g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
   //画边框
   g.setColor(new Color(33, 66, 99));
   g.drawRect(0, 0, width - 1, height - 1);
   // 随机产生干扰线，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 < mixTimes * codeLength / 10; i++) {
    if (ifMixColor) {
     g.setColor(getRandColor(160, 200));
    }
    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 < codeLength; i++) {
    String rand = String.valueOf(random.nextInt(10));
    sRand += rand;
    // 将认证码显示到图象中
    if (ifRandomColor)
     g.setColor(getRandColor(20, 110, 0));
    else
     g.setColor(bfColor);
    //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, 18 * 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, "PNG", response.getOutputStream());

   OutputStream toClient = response.getOutputStream();

        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(toClient);
        encoder.encode(image);

   toClient.close();
        out.clear();

   out = pageContext.pushBody();
} catch (Exception e) {
   e.printStackTrace();
}
%>
<%!//给定范围获得随机颜色
private static Random random = new Random();

private Color getRandColor(int fc, int bc) {
   return getRandColor(fc, bc, fc);
}

private Color getRandColor(int fc, int bc, int interval) {
   if (fc > 255) {
    fc = 255;
   }
   if (bc > 255) {
    bc = 255;
   }
   int r = fc + random.nextInt(bc - interval);
   int g = fc + random.nextInt(bc - interval);
   int b = fc + random.nextInt(bc - interval);
   return new Color(r, g, b);
}%>