Java生成验证码图片的程序

    package test;    import java.awt.Color;    import java.awt.Font;    import java.awt.Graphics;    import java.awt.image.BufferedImage;    import java.io.OutputStream;    import java.util.Random;    import javax.imageio.ImageIO;    import javax.servlet.http.HttpServlet;    import javax.servlet.http.HttpServletRequest;    import javax.servlet.http.HttpServletResponse;    public class ImageGenerator extends HttpServlet {      /** *//**       *       */      private static final long serialVersionUID = -3938318741402322164L;      private static Color getRandColor(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);      }      private static String charsLong = "23456789abcdefghjklmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";      private static String charsShort = "0123456789";      private static String chars = charsLong;      @Override      public void doGet(HttpServletRequest request, HttpServletResponse response) {        try {          int charsLength = chars.length();          response.setHeader("Pragma", "No-cache");          response.setHeader("Cache-Control", "no-cache");          response.setDateHeader("Expires", 0);          int width = 70, height = 20;          BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);          Graphics g = image.getGraphics();          Random random = new Random();          g.setColor(getRandColor(200, 250));          g.fillRect(0, 0, width, height);          g.setFont(new Font("Times New Roman", Font.ITALIC, height));          g.setColor(getRandColor(160, 200));          for (int i = 0; i < 35; 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);          }          StringBuilder sRand = new StringBuilder();          String[] fontNames = { "Times New Roman", "Arial", "Book antiqua", "" };          for (int i = 0; i < 4; i++) {            g.setFont(new Font(fontNames[random.nextInt(3)], Font.ITALIC, height));            char rand = chars.charAt(random.nextInt(charsLength));            sRand.append(rand);            g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));            g.drawString(String.valueOf(rand), 16 * i + random.nextInt(6) + 3, height - random.nextInt(4));          }          g.setColor(getRandColor(160, 200));          for (int i = 0; i < 30; i++) {            int x = random.nextInt(width);            int y = random.nextInt(height);            int xl = random.nextInt(width);            int yl = random.nextInt(width);            g.drawLine(x, y, x + xl, y + yl);          }          request.getSession().setAttribute("Login_Image_Code", sRand.toString());          g.dispose();          try {            Thread.sleep(100);          } catch (Exception ex) {          }          OutputStream os = response.getOutputStream();          ImageIO.write(image, "JPEG", os);          os.flush();          os.close();        } catch (Exception ex) {        }      }    }     修改 web.xml     <servlet>            <servlet-name>imageGenerator</servlet-name>            <servlet-class>test.ImageGenerator</servlet-class>        </servlet>        <servlet-mapping>            <servlet-name>imageGenerator</servlet-name>            <url-pattern>/image.jsp</url-pattern>        </servlet-mapping>