java生成验证码图片

public class AuthImg extends HttpServlet {

/**

*

*/

private static final long serialVersionUID = 4975974534946437434L;

// 设置图形验证码字符串的字体和大小

private Font mFont = new Font("微软雅黑", Font.ITALIC, 18);

private Random random = new Random();

public void init() throws ServletException {

super.init();

}

// 生成server响应的Service方法

public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

// 阻止生成的页面被缓存，保证每次都生成新的验证码

response.setHeader("Pragma", "No-cache");

response.setHeader("Cache-Control", "no-cache");

response.setDateHeader("Expires", 0);

response.setContentType("image/jpeg");

// 指定验证码图片的大小

int width = 80, height = 24;

// 生成一张新的图片

BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);

// 在图片中绘制内容

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));

// 该变量用于保存系统生成的随机变量字符串

String sRand = "";

int colorR = random.nextInt(200);

int colorG = random.nextInt(200);

int colorB = random.nextInt(200);

for (int i = 0; i < 4; i++) {

// 取得一个随机字符串

String tmp = getRandomChar();

sRand += tmp;

// 将系统生成的随机字符串加入到图片上

g.setColor(new Color(colorR, colorG, colorB));

g.drawString(tmp, 15 * i + 10, 20);

}

// 取得用户的Session

HttpSession session = request.getSession(true);

// 将系统生成的随机验证码加入到用户Session中

session.setAttribute("rand", sRand);

g.dispose();

// 输出验证码图片

ImageIO.write(image, "JPEG", response.getOutputStream());

}

// 生成随机字符串的方法

private String getRandomChar() {

int itmp = random.nextInt(10);

return String.valueOf(itmp);

}

}