val ttr attribute cep 隨機字符串 sta random pragma rac

public class AuthImg extends HttpServlet {

/**
*
*/
private static final long serialVersionUID = 4975974534946437434L;

// 設置圖形驗證碼字符串的字體和大小
private Font mFont = new Font("微軟雅黑", Font.ITALIC, 18);

private Random random = new Random();

public void init() throws ServletException {
super.init();
}

// 生成server響應的Service方法
public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 阻止生成的頁面被緩存，保證每次都生成新的驗證碼
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
response.setContentType("image/jpeg");
// 指定驗證碼圖片的大小
int width = 80, height = 24;
// 生成一張新的圖片
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);
// 在圖片中繪制內容
Graphics g = image.getGraphics();
g.setColor(new Color(252, 252, 252));
g.fillRect(1, 1, width, height);
g.setColor(new Color(252, 252, 252));
g.drawRect(0, 0, width, height);
g.setFont(mFont);
g.setColor(new Color(252, 252, 252));

// 該變量用於保存系統生成的隨機變量字符串
String sRand = "";
int colorR = random.nextInt(200);
int colorG = random.nextInt(200);
int colorB = random.nextInt(200);
for (int i = 0; i < 4; i++) {
// 取得一個隨機字符串
String tmp = getRandomChar();
sRand += tmp;
// 將系統生成的隨機字符串加入到圖片上
g.setColor(new Color(colorR, colorG, colorB));
g.drawString(tmp, 15 * i + 10, 20);
}
// 取得用戶的Session
HttpSession session = request.getSession(true);
// 將系統生成的隨機驗證碼加入到用戶Session中
session.setAttribute("rand", sRand);
g.dispose();
// 輸出驗證碼圖片
ImageIO.write(image, "JPEG", response.getOutputStream());
}

// 生成隨機字符串的方法
private String getRandomChar() {
int itmp = random.nextInt(10);
return String.valueOf(itmp);
}

}

java生成驗證碼圖片