Struts2验证码

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import com.sun.image.codec.jpeg.*;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class SafeCode extends HttpServlet {
    public void init() throws ServletException {
        super.init();
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
         //将图形写回给浏览器 
        response.setContentType("image/jpeg");
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Pragma", "No-cache");
        response.setDateHeader("Expires", 0L);
        HttpSession session = request.getSession();
        int width = 60; //图片宽度
        int height = 20; //图片高度
        // 在内存中构建一幅图像 
        BufferedImage image = new BufferedImage(width, height, 1);
        Graphics g = image.getGraphics();

        Random random = new Random();
        //设置图片颜色、字体
        g.setColor(getRandColor(200, 250));
        g.fillRect(0, 0, width, height);
        g.setFont(new Font("Arial", 0, 19));
        //设置图片的干扰线
        g.setColor(getRandColor(160, 200));
        for (int i = 0; i < 155; i++) {
            int x = random.nextInt(width + 100);
            int y = random.nextInt(height + 100);
            int xl = random.nextInt(10);
            int yl = random.nextInt(12);
            g.drawOval(x, y, x + xl, y + yl);
        }

        String sRand = "";
        for (int i = 0; i < 4; i++) {
            String rand = getRandChar(random.nextInt(36));
            sRand = sRand + rand;
            g.setColor(new Color(20 + random.nextInt(110), 20 + random
                    .nextInt(110), 20 + random.nextInt(110)));
            g.drawString(rand, 13 * i + 6, 16);
        }

        session.setAttribute("rand", sRand);
        g.dispose();

        javax.servlet.ServletOutputStream imageOut = response.getOutputStream();
        ImageIO.write(image, "jpeg", imageOut);

    }

    public void destroy() {
    }

    private 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);
    }

    private String getRandChar(int randNumber) {
        return CHARARRAY[randNumber];
    }

    //private static final String CONTENT_TYPE = "image/jpeg";
    private static final String CHARARRAY[] = { "0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "a", "b", "c", "d", "e", "f", "g", "h", "i",
            "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v",
            "w", "x", "y", "z" };

}