JAVA验证码[含字母数字]

import java.awt.Color;import java.awt.Font;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.*;import java.io.*;import javax.servlet.http.*;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class RandomCode extends HttpServlet {/** * The doGet method of the servlet. <br> * * This method is called when a form. has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request, response);}/** * The doPost method of the servlet. <br> * * This method is called when a form. has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {// 验证码图片的宽度。int width = 70;//验证码图片的高度。int height = 36;BufferedImage 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();// 设定图像背景色(因为是做背景，所以偏淡)g.setColor(getRandColor(180, 250));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("Times New Roman", Font.PLAIN, 28);//设置字体。g.setFont(font);//画边框。g.setColor(Color.BLACK);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 < 50; i++) {int x = random.nextInt(width);int y = random.nextInt(height);int xl = random.nextInt(12);int yl = random.nextInt(12);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();// 设置默认生成4个验证码int length = 4;// 设置备选验证码:包括"a-z"和数字"0-9"String base = "abcdefghijklmnopqrstuvwxyz0123456789";int size = base.length();//随机产生4位数字的验证码。for (int i = 0; i < length; i++) {//得到随机产生的验证码数字。int start = random.nextInt(size);String strRand = base.substring(start, start + 1);//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));// 生成随机颜色(因为是做前景，所以偏深)g.setColor(getRandColor(1, 100));g.drawString(strRand, 13 * i + 6, 28);//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。HttpSession session = request.getSession();session.setAttribute("rand", 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.close();}Color getRandColor(int fc, int bc) {//给定范围获得随机颜色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);}}