Java generates a Random verification code (supporting uppercase/lowercase letters, numbers, and random fonts ).

The Code is as follows:

Copy codeThe Code is as follows: package com. hoo. util;

Import java. awt. Color;
Import java. awt. Font;
Import java. awt. Graphics;
Import java. awt. image. BufferedImage;
Import java. util. Random;

Import javax. imageio. ImageIO;
Import javax. servlet. http. HttpServletRequest;
Import javax. servlet. http. HttpServletResponse;
/**
* <B> function: </B> Verification Code Generation Tool
* @ Project NetWorkService
* @ Package com. hoo. util
* @ FileName ValidCodeUtils. java
* @ CreateDate 03:05:50 pm
* @ Author hoojo
*/
@ SuppressWarnings ("unused ")
Public class ValidCodeUtils {
/*************************************** ******************************
* Verification Code width
*/
Public static int WIDTH = 60;
/***
* Verification Code height
*/
Public static int HEIGHT = 20;

/*************************************** *******************************
* The Verification Code background color COLOR_FC_BG should be smaller than COLOR_BC_BG
*/
Public static int COLOR_FC_BG = 200;
/***
* The Verification Code background color COLOR_FC_BG should be smaller than COLOR_BC_BG
*/
Public static int COLOR_BC_BG = 250;

/*************************************** *******************************
* The Color of the Verification Code background interference line COLOR_FC_LINE should be smaller than COLOR_BC_LINE
*/
Public static int COLOR_FC_LINE = 160;
/***
* The Color of the Verification Code background interference line COLOR_FC_LINE should be smaller than COLOR_BC_LINE
*/
Public static int COLOR_BC_LINE = 200;

/*************************************** ************************************
* The verification code color COLOR_FC_CODE should be smaller than COLOR_BC_CODE
*/
Public static int COLOR_FC_CODE = 20;
/***
* The verification code color COLOR_FC_CODE should be smaller than COLOR_BC_CODE
*/
Public static int COLOR_BC_CODE = 170;

/*************************************** ************************************
* Generate colors in the specified range
* @ Param fc: The fc color value is less than 255.
* @ Param bc the bc color value is less than 255
* @ Return Color
*/
Private static Color getRandColor (int fc, int bc ){
Random random = new Random ();
If (fc <0)
Fc = 0;
If (bc <0)
Bc = 1;
If (fc> 255)
Fc = 255;
If (bc> 255)
Bc = 255;
If (bc = fc)
Bc + = 10;
Int temp = 0;
If (bc <fc ){
Temp = bc;
Bc = fc;
Fc = temp;
}
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 );
}

/**
* <B> function: </B> Image Generation Method
* @ CreateDate 03:06:22 pm
* @ Author hoojo
* @ Param request HttpServletRequest
* @ Param response HttpServletResponse
* @ Return boolean
* @ Throws Exception
*/
Public static boolean getImage (HttpServletRequest request, HttpServletResponse response) throws Exception {
Response. reset ();
Response. setContentType ("image/jpeg ");
// Set the page not to cache
Response. setHeader ("Pragma", "No-cache ");
Response. setHeader ("Cache-Control", "no-cache ");
Response. setDateHeader ("Expires", 0 );
// Create an image in memory
BufferedImage image = new BufferedImage (WIDTH, HEIGHT, BufferedImage. TYPE_INT_RGB );

// Obtain the image Context
Graphics img = image. getGraphics ();
// Generate a random class
Random random = new Random ();

// Set the background color
Img. setColor (getRandColor (COLOR_FC_BG, COLOR_BC_BG ));
Img. fillRect (0, 0, WIDTH, HEIGHT );

// Set the font
Img. setFont (new Font ("Times New Roman", Font. PLAIN, 18 ));

// Draw a border
// G. setColor (new Color ());
// G. drawRect (0, 0, width-1, height-1 );

// Generates 155 random interference lines, making the authentication code in the image hard to be detected by other programs.
Img. setColor (getRandColor (COLOR_FC_LINE, COLOR_BC_LINE ));
For (int I = 0; I <155; I ++ ){
Int x = random. nextInt (WIDTH );
Int y = random. nextInt (HEIGHT );
Int xl = random. nextInt (12 );
Int yl = random. nextInt (12 );
Img. drawLine (x, y, x + xl, y + yl );
}

// Obtain the random ID code (4 digits)
String codeValue = "";
For (int I = 0; I <4; I ++ ){
// String rand = String. valueOf (random. nextInt (10 ));
String rand = getRandomChar ();
CodeValue = codeValue. concat (rand );
Img. setFont (getRandomFont (); // random font
// Display the authentication code to the image
Img. setColor (getRandColor (COLOR_FC_CODE, COLOR_BC_CODE ));
Img. drawString (rand, 13 * I + 6, 16 );
}
Request. getSession (). setAttribute ("codeValue", codeValue );
// The image takes effect
Img. dispose ();
// Output the image to the page
Return ImageIO. write (image, "JPEG", response. getOutputStream ());
}

/**
* Randomly generated characters, including uppercase letters, lowercase letters, and numbers
* <B> function: </B> function
* @ CreateDate 2010-8-23 10:33:55 AM
* @ Author hoojo
* @ Return
*/
Public static String getRandomChar (){
Int index = (int) Math. round (Math. random () * 2 );
String randChar = "";
Switch (index ){
Case 0: // uppercase characters
RandChar = String. valueOf (char) Math. round (Math. random () * 25 + 65 ));
Break;
Case 1: // lowercase characters
RandChar = String. valueOf (char) Math. round (Math. random () * 25 + 97 ));
Break;
Default: // number
RandChar = String. valueOf (Math. round (Math. random () * 9 ));
Break;
}
Return randChar;
}

/**
* <B> function: </B> the font and text size are randomly generated.
* @ CreateDate 2010-8-23 10:44:22 AM
* @ Author hoojo
* @ Return
*/
Public static Font getRandomFont (){
String [] fonts = {"Georgia", "Verdana", "Arial", "Tahoma", "Time News Roman", "Courier New", "Arial Black ", "Quantzite "};
Int fontIndex = (int) Math. round (Math. random () * (fonts. length-1 ));
Int fontSize = (int) Math. round (Math. random () * 4 + 16 );
Return new Font (fonts [fontIndex], Font. PLAIN, fontSize );
}
}

The verification code value is saved in the session: request. getSession (). setAttribute ("codeValue", codeValue );
Check whether the value entered by the user is equal to the codeValue in the session;

The following is a jsp page call servlet: ValidCodeServlet. java

ValidCodeServlet calls the above ValidCodeUtils Verification Code Generation Tool class

Package com. hoo. servlet;

Import java. io. IOException;
Import javax. servlet. ServletException;
Import javax. servlet. http. HttpServlet;
Import javax. servlet. http. HttpServletRequest;
Import javax. servlet. http. HttpServletResponse;

Import com. hoo. util. ValidCodeUtils;

@ SuppressWarnings ("serial ")
Public class ValidCodeServlet extends HttpServlet {

Public void doGet (HttpServletRequest request, HttpServletResponse response)
Throws ServletException, IOException {
Try {
ValidCodeUtils. getImage (request, response );
} Catch (Exception e ){
E. printStackTrace ();
}
}

Public void doPost (HttpServletRequest request, HttpServletResponse response)
Throws ServletException, IOException {
DoGet (request, response );
}
}

Call the servlet method on the jsp page.

Js: reloadValidCode Method

Function reloadValidCode (o ){
O. src = "$ {pageContext. request. contextPath}/validCodeServlet? Timed = "+ new Date (). getMilliseconds ();
}
Here, "timed =" + new Date (). getMilliseconds (); is used to prevent IE cache.

Html Tag:

You can directly configure the url with the Servlet name, which corresponds to the web. xml configuration. The main call path $ {pageContext. request. contextPath}/validCodeServlet will carry the root directory, which is relatively safe.

ValidCodeServlet configuration in web. xml
<Servlet>
<Servlet-name> validCodeServlet </servlet-name>
<Servlet-class> com. hoo. servlet. ValidCodeServlet </servlet-class>
</Servlet>

<Servlet-mapping>
<Servlet-name> validCodeServlet </servlet-name>
<Url-pattern>/validCodeServlet </url-pattern>
</Servlet-mapping>