Servlet生成隨機驗證碼

 

package book.servlet;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.p_w_picpath.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.p_w_picpathio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 生成圖形驗證碼的Servlet
 */
public class ImageCodeMakerServlet extends HttpServlet {

    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doPost(req, resp);
    }

    /**
     * @see javax.servlet.http.HttpServlet#void
     *      (javax.servlet.http.HttpServletRequest,
     *      javax.servlet.http.HttpServletResponse)
     */
    public void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

        System.out.println("和峨峨峨峨峨峨峨峨峨峨");
        // 首先設置頁面不緩存
        resp.setHeader("Pragma", "No-cache");
        resp.setHeader("Cache-Control", "no-cache");
        resp.setDateHeader("Expires", 0);

        // 定義圖片的寬度和高度
        int width = 90, height = 40;
        // 創建一個圖像對象
        BufferedImage p_w_picpath = new BufferedImage(width, height,
                BufferedImage.TYPE_INT_RGB);
        // 得到圖像的環境對象
        Graphics g = p_w_picpath.createGraphics();

        Random random = new Random();
        // 用隨機顏色填充圖像背景
        g.setColor(getRandColor(180, 250));
        g.fillRect(0, 0, width, height);
        for (int i = 0; i < 5; i++) {
            g.setColor(getRandColor(50, 100));
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            g.drawOval(x, y, 4, 4);
        }
        // 設置字體，下面準備畫隨機數
        g.setFont(new Font("", Font.PLAIN, 40));
        // 隨機數字符串
        String sRand = "";
        for (int i = 0; i < 4; i++) {
            // 生成四個數字字符
            String rand = String.valueOf(random.nextInt(10));
            sRand += rand;
            // 生成隨機顏色
            g.setColor(new Color(20 + random.nextInt(80), 20 + random
                    .nextInt(100), 20 + random.nextInt(90)));
            // 將隨機數字畫在圖像上
            g.drawString(rand, (17 + random.nextInt(3)) * i + 8, 34);

            // 生成干擾線
            for (int k = 0; k < 12; k++) {
                int x = random.nextInt(width);
                int y = random.nextInt(height);
                int xl = random.nextInt(9);
                int yl = random.nextInt(9);
                g.drawLine(x, y, x + xl, y + yl);
            }
        }

        // 將生成的隨機數字字符串寫入Session
        req.getSession().setAttribute("randcode", sRand);
        // 使圖像生效
        g.dispose();
        // 輸出圖像到頁面
        ImageIO.write(p_w_picpath, "JPEG", resp.getOutputStream());
    }

    /**
     * 產生一個隨機的顏色
     * @param fc    顏色分量最小值
     * @param bc    顏色分量最大值
     * @return
     */
    public Color getRandColor(int fc, int bc) {
        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);
    }
}