User Logon Random verification code and user logon Verification Code

User Logon Random verification code and user logon Verification Code

1 public class CheckImage extends HttpServlet {2 // The width of the Verification Code image. 3 private int width = 94; 4 // height of the Verification Code image. 5 private int height = 44; 6 protected void service (HttpServletRequest req, HttpServletResponse resp) 7 throws ServletException, java. io. IOException {8 BufferedImage buffImg = new BufferedImage (width, height, BufferedImage. TYPE_INT_RGB); 9 Graphics2D g = buffImg. createGraphics (); 10 // create a random number generator class. 11 Random random = new Random (); 12g. setColor (Color. WHITE); 13g. fillRect (, width, height); 14 // create a font. The font size depends on the Image height. 15 Font font = new Font ("Times New Roman", Font. PLAIN, 36); 16 // set the Font. 17g. setFont (font); 18 // draw the border. 19g. setColor (Color. BLACK); 20g. drawRect (160, width-1, height-1); 21 22 // generates random interference lines, making the identification code in the image hard to be detected by other programs. 23g. setColor (Color. GRAY); 24 for (int I = 0; I <160; I ++) {25 int x = random. nextInt (width); 26 int y = random. nextInt (height); 27 int xl = random. nextInt (12); 28 int yl = random. nextInt (12); 29g. drawLine (x, y, x + xl, y + yl); 30} 31 32 // randomCode is used to save the randomly generated verification code so that the user can perform verification after login. 33 StringBuffer randomCode = new StringBuffer (); 34 int red = 0, green = 0, blue = 0; 35 // a four-digit verification code is randomly generated. 36 for (int I = 0; I <4; I ++) {37 // obtain the randomly generated verification code number. 38 String strRand = String. valueOf (random. nextInt (10); 39 // generate a random color component to construct the color value, so that the color value of each output number will be different. 40 red = random. nextInt (210); 41 green = random. nextInt (150); 42 blue = random. nextInt (150); 43 // use a random color to plot the verification code into the image. 44g. setColor (new Color (red, green, blue); 45g. drawString (strRand, 20 * I + 8, 36); 46 // combine the four random numbers. 47 randomCode. append (strRand); 48} 49 // Save the four-digit verification code to the Session. 50 HttpSession session = req. getSession (); 51 session. setAttribute ("validate", randomCode. toString (); 52 // disable image caching. 53 resp. setHeader ("Pragma", "no-cache"); 54 resp. setHeader ("Cache-Control", "no-cache"); 55 resp. setDateHeader ("Expires", 0); 56 resp. setContentType ("image/jpeg"); 57 // output the image to the Servlet output stream. 58 ServletOutputStream sos = resp. getOutputStream (); 59 ImageIO. write (buffImg, "jpeg", sos); 60 sos. close (); 61} 62}