圖片驗證碼jsp

前段時間項目中用的圖片驗證碼。有很多開源的圖片校驗，用jquery寫的。但後來都沒采納，採納了一個最簡單的，拿出來和大家分享下

<%@ page language="java" contentType="image/jpeg" pageEncoding="utf-8"%>
<%@ page contentType="image/jpeg"
import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%@ page import="java.io.OutputStream"%>
<%!Color getRandColor(int fc, int bc)
    {
        //給定範圍獲得隨機顏色 
        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);
    }%>
<%
    try
    {
        //設置頁面不緩存 
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        // 在內存中創建圖象 
        int width = 60, height = 20;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        OutputStream os = response.getOutputStream();
        // 獲取圖形上下文 
        Graphics g = image.getGraphics();
        //生成隨機類 
        Random random = new Random();
        // 設定背景色 
        g.setColor(getRandColor(200, 250));
        g.fillRect(0, 0, width, height);
        //設定字體 
        g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
        //畫邊框 
        //g.setColor(new Color()); 
        //g.drawRect(0,0,width-1,height-1); 
        // 隨機產生155條幹擾線，使圖象中的認證碼不易被其它程序探測到 
        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);
        }
        // 取隨機產生的認證碼(4位數字) 
        String sRand = "";
        for (int i = 0; i < 4; i++ )
        {
            //String rand=String.valueOf(random.nextInt(10));  //數字 
            //String rand=String.valueOf((char)(Math.round(Math.random() * 25 + 65))); //字母大寫 http://www.itstudy.cn/ 
            String rand = String.valueOf((char) (Math.round(Math.random() * 25 + 97))); //字母小寫 
            sRand += rand;
            // 將認證碼顯示到圖象中 
            g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110),
                20 + random.nextInt(110)));
            //調用函數出來的顏色相同，可能是因爲種子太接近，所以只能直接生成 
            g.drawString(rand, 13 * i + 6, 16);
        }
        // 將認證碼存入SESSION 
        session.setAttribute("rand", sRand);
        // 圖象生效 
        g.dispose();
        // 輸出圖象到頁面 
        ImageIO.write(image, "JPEG", os);
        os.flush();
        os.close();
        os = null;
        response.flushBuffer();
        out.clear();
        out = pageContext.pushBody();
    }
    catch (IllegalStateException e)
    {
        System.out.println(e.getMessage());
        e.printStackTrace();
    }
%>