Session JavaWeb implemented using disposable codes

 

Forms

<form action="loginServlet" method="post">
  请输入验证码：<input type="text" name="code" />
  <img src="getCodeServlet" /><br />
  <button type="submit">提交</button>
</form>

When the page is loaded, it will automatically request getCodeServlet, get the picture (verification code).

 

 

 

getCodeServlet, generating codes

. 1 @WebServlet ( "/ getCodeServlet" )
 2  public  class GetCodeServlet the extends the HttpServlet {
 . 3      // codes width and height 
. 4      Private  static  int WIDTH = 80 ;
 . 5      Private  static  int HEIGHT = 25 ;
 . 6  
. 7      // draw the background 
. 8      Private  void drawBg (Graphics G) {
 . 9          // RGB 
10          g.setColor ( new new Color (128, 128, 128 ));
 . 11          // draw a rectangle. X, Y, wigth, height 
12 is         g.fillRect (0,0 , WIDTH, HEIGHT);
 13 is          // random interference map 100 points 
14          the Random Random = new new the Random ();
 15          for ( int I = 0; I <100; I ++ ) {
 16              // generated the decimal (0,1), * WIDTH | HEIGHT , then rounding will do 
. 17              int X = random.nextInt (WIDTH);
 18 is              int Y = random.nextInt (HEIGHT);
 . 19              g.drawOval (X, Y, 1,1 );
 20 is  
21 is              // color interference point may be randomly, randomly generated red, green, blue can
 22 is              // g.setColor (new new color (red, green, blue)); 
23 is          }
 24     }
 25  
26 is  
27      // Draw codes 
28      Private  void drawCode (G Graphics, char [] code) {
 29          g.setColor (as Color.BLACK.);
 30          // font, style (when a plurality of vertical partition), size 
31          g.setFont ( new new the Font ( "serif", Font.ITALIC | Font.BOLD, 18 is ));
 32          // draw character codes, parameters at different locations: to draw a String, horizontal and vertical coordinates. + "" To turn char String. 
33 is          g.drawString (code [0] + "", 1,17 );
 34 is          g.drawString (code [. 1] + "", 16,15 );
 35          g.drawString (code [2] + "", 31 is , 18 );
 36         g.drawString (code [. 3] + "", 46,16 );
 37 [      }
 38 is  
39      // randomly generates four codes 
40      Private  char [] the getCode () {
 41 is          String chars = "0123456789QWERTYUIOPASDFGHJKLZXCVBNMqwertyuiopasdfghjklzxcvbnm" ;
 42 is          char [] = code new new  char [. 4 ];
 43 is          the Random Random = new new the Random ();
 44 is          for ( int I = 0; I <. 4; I ++ ) {
 45              // [0,62) 
46 is              int index = random.nextInt (62 is ) ;
 47             code[i]=chars.charAt(index);
48         }
49         return code;
50     }
51 
52 
53     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
54         HttpSession session = request.getSession();
55         ServletOutputStream sos = response.getOutputStream();
56         response.setContentType("image/jpeg");
57 
58         //设置浏览器不缓存此图片
59         response.setHeader("Pragma","No-cache");
60          response.setHeader ( "the Cache-Control", "Cache-NO" );
 61 is          . Response.setDateHeader ( "the Expires", 0 );
 62 is  
63 is          // Create image memory 
64          the BufferedImage BufferedImage = new new the BufferedImage (WIDTH, HEIGHT, TYPE_INT_RGB that) ;
 65          Graphics G = bufferedImage.getGraphics ();
 66          char [] code = the getCode ();
 67          // the session codes in a domain. To obtain a session object prior to submission response 
68          session.setAttribute ( "code", new new String (code));
 69          drawBg (G);
 70          drawCode (G, code);
71         g.dispose();
72 
73         //将图片输出到浏览器
74         ByteArrayOutputStream baos = new ByteArrayOutputStream();
75         ImageIO.write(bufferedImage,"JPEG",baos);
76         baos.writeTo(sos);
77         baos.close();
78         sos.close();
79     }
80 
81     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
82         doPost(request,response);
83     }
84 }

 

 

 

loginServlet, form processing

 1 @WebServlet("/loginServlet")
 2 public class LoginServlet extends HttpServlet {
 3     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 4         response.setContentType("text/html;charset=utf-8");
 5         HttpSession session = request.getSession();
 6         String trueCode= (String) session.getAttribute("code");
 7         String code=request.getParameter("code");
 8 
 9         if (code.equals(trueCode)){
10             response.getWriter().write("验证码正确");
11         }
12         else {
13             response.getWriter().write("验证码错误");
14         }
15     }
16 
17     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
18         doPost(request,response);
19     }
20 }

 

The above approach is case sensitive codes.

 

not case sensitive:

// first converted to all uppercase | lowercase, and then determine 
        trueCode = trueCode.toLowerCase (); 
        code = code.toLowerCase (); 

        // trueCode = trueCode.toUpperCase ();
         // code = trueCode.toUpperCase ();