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JSP Verification Code

Source: Internet
Author: User
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The implementation of the verification code is divided into two parts: JSP page and Java Servlet:

JSP page:

<! DOCTYPE html>

<Html>

<Head>

<Title> loginForm.html </title>

 

<Meta http-equiv = "keywords" content = "keyword1, keyword2, keyword3">

<Meta http-equiv = "description" content = "this is my page">

<Meta http-equiv = "content-type" content = "text/html; charset = UTF-8">

<! -- <Link rel = "stylesheet" type = "text/css" href = "./styles.css"> -->

</Head>

 

<Body>

<H3> login page with verification code

<Form method = "post" action = "login. yan">

Username: <input type = "text" name = "usreName" size = "10"> <br/>

Password & nbsp; Code: <input type = "password" name = "password" size = "10"> <br>

Verification Code: <input type = "text" name = "userNum" size = "4"> <br/>

<Input type = "submit" value = "submit">

</Form>

</Body>

</Html>

 

Java class:

Package com. csdn. session;

Import java. awt. Color;

Import java. awt. Font;

Import java. awt. Graphics;

Import java. awt. image. BufferedImage;

Import java. io. ByteArrayOutputStream;

Import java. io. IOException;

Import javax. imageio. ImageIO;

Import javax. servlet. ServletException;

Import javax. servlet. ServletOutputStream;

Import javax. servlet. http. HttpServlet;

Import javax. servlet. http. HttpServletRequest;

Import javax. servlet. http. HttpServletResponse;

Import javax. servlet. http. HttpSession;

Public class loginForm extends HttpServlet {

Private static final long serialVersionUID = 1L;

Public void doGet (HttpServletRequest request, HttpServletResponse response)

Throws ServletException, IOException {

DoPost (request, response );

}

 

Private static int WIDTH = 80;

Private static int HEIGHT = 20;

Public void doPost (HttpServletRequest request, HttpServletResponse response)

Throws ServletException, IOException {

Response. setContentType ("image/jpeg ");

 

ServletOutputStream out = response. getOutputStream ();

 

// PrintWriter out = response. getWriter ();

Response. setHeader ("Pragma", "no-cache ");

Response. setHeader ("Cache-Controll", "no-cache ");

Response. setIntHeader ("Expires", 0 );

// Background

 

BufferedImage bi = new BufferedImage (WIDTH, HEIGHT, BufferedImage. TYPE_INT_RGB );

Graphics g = bi. getGraphics ();

DrawBackground (g );

 

// Generate a random Verification Code

Char [] rands = generateCheckCode ();

 

// System. out. println (fun (rands ));

 

HttpSession session = request. getSession ();

 

Session. setAttribute ("num", fun (rands) + ""); // verification code = 12-9 = 3; write the sesion object

 

DrawRands (g, rands );

 

ByteArrayOutputStream bos = new ByteArrayOutputStream ();

 

ImageIO. write (bi, "JPEG", bos );

 

Byte [] buf = bos. toByteArray (); // convert the content of the bi object into characters

 

Out. write (buf );

 

Response. setContentLength (buf. length );

 

Out. flush ();

Out. close ();

}

 

 

Private int fun (char [] rands ){

 

Int num1 = Integer. parseInt (rands [0] + "") * 10 + Integer. parseInt (rands [1] + "");

Int num2 = Integer. parseInt (rands [2] + "");

Int num = 0;

If (rands [2] = '+ '){

Num = num1 + num2;

} Else {

Num = num1-num2;

}

 

Return num;

 

}

 

 

Private void drawRands (Graphics g, char [] rands ){

 

G. setColor (Color. black );

G. setFont (new Font (null, Font. ITALIC | Font. BOLD, 18 ));

 

G. drawString ("" + rands [0], 1, 20 );

G. drawString ("" + rands [1], 14,17 );

G. drawString ("" + rands [3], 30,16 );

G. drawString ("" + rands [2], 42,18 );

G. drawString ("" + rands [4], 56,16 );

 

}

 

Private char [] generateCheckCode (){

 

String chars = "0123456789 ";

String char1 = "+ -";

Char [] rands = new char [5];

Rands [0] = chars. charAt (int) (Math. random () * 2) + 1 );

Rands [1] = chars. charAt (int) (Math. random () * 10 ));

Rands [2] = chars. charAt (int) (Math. random () * 9) + 1 );

Rands [3] = char1.charAt (int) (Math. random () * 2 ));

Rands [4] = ';

Return rands;

}

 

Private void drawBackground (Graphics g ){

G. setColor (new Color (0 XDCDCDC ));

 

G. fillRect (0, 0, WIDTH, HEIGHT );

 

For (int I = 0; I <20; I ++ ){

Int x = (int) (Math. random () * WIDTH );

Int y = (int) (Math. random () * HEIGHT );

Int red = (int) (Math. random () * 255 );

Int greed = (int) (Math. random () * 255 );

Int blue = (int) (Math. random () * 255 );

G. setColor (new Color (red, greed, blue ));

G. drawOval (x, y, 1, 0 );

}

 

}

}

From song lixing's column

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

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