Servlet 实现随机验证码

/**   * To change this template, choose Tools | Templates   * and open the template in the editor.   */  package net.individuals.web.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.annotation.WebServlet;  import javax.servlet.http.HttpServlet;  import javax.servlet.http.HttpServletRequest;  import javax.servlet.http.HttpServletResponse;    /**   *   * @author Barudisshu   */  @WebServlet(name = "ImageCodeMakerServlet", urlPatterns = {"/ImageCodeMakerServlet"})  public class ImageCodeMakerServlet extends HttpServlet {        /**       * Processes requests for both HTTP       * <code>GET</code> and       * <code>POST</code> methods.       *       * @param request servlet request       * @param response servlet response       * @throws ServletException if a servlet-specific error occurs       * @throws IOException if an I/O error occurs       */      protected void processRequest(HttpServletRequest request, HttpServletResponse response)              throws ServletException, IOException {          //设置页面不缓存          response.setHeader("Pragma", "No-cache");          response.setHeader("Cache-Control", "No-cache");          //设置有效期          response.setDateHeader("Expires", 0);            //设置图片的宽度和高度          int width = 60, height = 20;            //创建一个图像对象          BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);            //获取画图对象          Graphics g = image.createGraphics();            //创建随机对象          Random random = new Random();            //用随机颜色填充图像背景          g.setColor(new Color(255, 255, 255));            //图像形状          g.fillRect(0, 0, width, height);            //设置字体          g.setFont(new Font("Tahoma", Font.PLAIN, 20));            //随机数字符串          String sRand = "";            for (int i = 0; i < 4; i++) {              //生成四个数字字符              String rand = String.valueOf(random.nextInt(10));              sRand += rand;              //生成随机颜色              g.setColor(new Color(100 + random.nextInt(155), random.nextInt(100), 100 + random.nextInt(155)));              //将随机数字画在图像上              g.drawString(rand, (12 + random.nextInt(2)) * i + 6, 18);          }            //生成干扰线          for (int k = 0; k < 24; k++) {              g.setColor(getRandomColor(0, 255));              int x = random.nextInt(width);              int y = random.nextInt(height);              int x1 = random.nextInt(6);              int y1 = random.nextInt(6);              g.drawLine(x, y, x + x1, y + y1);          }                    //生成干扰像素点          for (int i = 0; i < 10; i++) {              g.setColor(getRandomColor(50, 180));              int x = random.nextInt(width);              int y = random.nextInt(height);              g.drawOval(x, y, 1, 1);          }                    //将生成的随机数字写入Session会话          request.getSession().setAttribute("randcode", sRand);            //使图像生效          g.dispose();            //输出图像到页面          ImageIO.write(image, "JPEG", response.getOutputStream());        }        /**       * 产生一个随机颜色       *       * @param fc 颜色分量最小值       * @param bc 颜色分量最大值       * @return       */      public Color getRandomColor(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);      }        // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">      /**       * Handles the HTTP       * <code>GET</code> method.       *       * @param request servlet request       * @param response servlet response       * @throws ServletException if a servlet-specific error occurs       * @throws IOException if an I/O error occurs       */      @Override      protected void doGet(HttpServletRequest request, HttpServletResponse response)              throws ServletException, IOException {          processRequest(request, response);      }        /**       * Handles the HTTP       * <code>POST</code> method.       *       * @param request servlet request       * @param response servlet response       * @throws ServletException if a servlet-specific error occurs       * @throws IOException if an I/O error occurs       */      @Override      protected void doPost(HttpServletRequest request, HttpServletResponse response)              throws ServletException, IOException {          processRequest(request, response);      }        /**       * Returns a short description of the servlet.       *       * @return a String containing servlet description       */      @Override      public String getServletInfo() {          return "Short description";      }// </editor-fold>  }