jsp 生成網頁驗證碼的Servlet

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 javax.imageio.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 {
// 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 image = new BufferedImage(width, height,

BufferedImage.TYPE_INT_RGB);

// 得到圖像的環境對象
Graphics g = image.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(image, "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);
}
}
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