Java的servlet生成动态验证码

代码：

/** * @class 验证码 */import java.awt.Color;import java.awt.Font;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class ValidateCodeServlet extends HttpServlet {// 常量private static final long serialVersionUID = 1L;// 验证码图片的宽度。private int width = 60;// 验证码图片的高度。private int height = 20;// 验证码字符个数private int codeCount = 4;private int x = 0;// 字体高度private int fontHeight;private int codeY;char[] codeSequence = {'0','1', '2', '3', '4', '5', '6', '7', '8', '9'};/*{ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J','K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W','X', 'Y', 'Z', '1', '2', '3', '4', '5', '6', '7', '8', '9','a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm','n',  'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z' };*//** * 构造方法 */public ValidateCodeServlet() {super();}/** * 初始化 */public void init() throws ServletException {// 宽度String strWidth = this.getInitParameter("width");// 高度String strHeight = this.getInitParameter("height");// 字符个数String strCodeCount = this.getInitParameter("codeCount");// 将配置的信息转换成数值try {if (strWidth != null && strWidth.length() != 0) {width = Integer.parseInt(strWidth);}if (strHeight != null && strHeight.length() != 0) {height = Integer.parseInt(strHeight);}if (strCodeCount != null && strCodeCount.length() != 0) {codeCount = Integer.parseInt(strCodeCount);}} catch (NumberFormatException e) {}x = width / (codeCount + 2);fontHeight = height - 1;codeY = height - 4;}/** * 服务 */public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request, response);}/** * 服务 */public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// 定义图像bufferBufferedImage buffImg = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);Graphics2D g = buffImg.createGraphics();// 创建一个随机数生成器类Random random = new Random();// 将图像填充为白色g.setColor(Color.WHITE);g.fillRect(0, 0, width, height);// 创建字体，字体的大小应该根据图片的高度来定。Font font = new Font("宋体", Font.BOLD, fontHeight);// 设置字体。g.setFont(font);// 画边框。g.setColor(Color.GRAY);g.drawRect(0, 0, width - 1, height - 1);// 随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。g.setColor(Color.GRAY);for (int i = 0; i < 40; i++) {int x = random.nextInt(width);int y = random.nextInt(height);int xl = random.nextInt(2);int yl = random.nextInt(2);g.drawLine(x, y, x + xl, y + yl);}// randomCode用于保存随机产生的验证码，以便用户登录后进行验证。StringBuffer randomCode = new StringBuffer();int red = 0, green = 0, blue = 0;// 随机产生codeCount数字的验证码。for (int i = 0; i < codeCount; i++) {// 得到随机产生的验证码数字。String strRand = String.valueOf(codeSequence[random.nextInt(10)]);// 产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同。red = random.nextInt(127);green = random.nextInt(127);blue = random.nextInt(127);// 用随机产生的颜色将验证码绘制到图像中。g.setColor(new Color(red, green, blue));g.drawString(strRand, (i + 1) * x, codeY);// 将产生的四个随机数组合在一起。randomCode.append(strRand);}// 将四位数字的验证码保存到Session中。request.getSession().setAttribute("validateCode", randomCode.toString());System.out.println("----------------------->动态生成了验证码:"+randomCode.toString());//session.setAttribute("validateCode", randomCode.toString());// 禁止图像缓存。response.setHeader("Pragma", "no-cache");response.setHeader("Cache-Control", "no-cache");response.setDateHeader("Expires", 0);response.setContentType("image/jpeg");// 将图像输出到Servlet输出流中。ServletOutputStream sos = response.getOutputStream();ImageIO.write(buffImg, "jpeg", sos);sos.flush();sos.close();}/** * 销毁 */public void destroy() {super.destroy();}}