Verification code implementation --- (servlet verification code)

Step 1: create a dynamic project check, a check. Java (servlet class), and a login. jsp file

Step 2: Compile the check. Java file with the following content:

01.package check;  02.import javax.servlet.ServletException;  03.import javax.servlet.http.*;  04.import java.io.*;  05.import java.awt.*;  06.import java.awt.image.*;  07.import java.util.*;  08.import javax.imageio.*;   09.  10./** 11. * @author  yeeku.H.lee kongyeeku@163.com 12. * @version  1.0 13. * <br>Copyright (C), 2005-2008, yeeku.H.Lee 14. * <br>This program is protected by copyright laws. 15. * <br>Program Name: 16. * <br>Date:  17. */  18.public class check extends HttpServlet  19.{  20.    private Font mFont = new Font("Arial Black", Font.PLAIN, 16);  21.    public void init() throws ServletException  22.    {  23.        super.init();  24.    }  25.    Color getRandColor(int fc,int bc)  26.    {  27.        Random random = new Random();  28.        if(fc>255) fc=255;  29.        if(bc>255) bc=255;  30.        int r=fc+random.nextInt(bc-fc);  31.        int g=fc+random.nextInt(bc-fc);  32.        int b=fc+random.nextInt(bc-fc);  33.        return new Color(r,g,b);  34.    }  35.  36.    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException  37.    {  38.        response.setHeader("Pragma","No-cache");  39.        response.setHeader("Cache-Control","no-cache");  40.        response.setDateHeader("Expires", 0);  41.        response.setContentType("image/jpeg");  42.          43.        int width=100, height=18;  44.        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);  45.          46.        Graphics g = image.getGraphics();  47.        Random random = new Random();  48.        g.setColor(getRandColor(200,250));  49.        g.fillRect(1, 1, width-1, height-1);  50.        g.setColor(new Color(102,102,102));  51.        g.drawRect(0, 0, width-1, height-1);  52.        g.setFont(mFont);  53.  54.        g.setColor(getRandColor(160,200));  55.        for (int i=0;i<155;i++)  56.        {  57.            int x = random.nextInt(width - 1);  58.            int y = random.nextInt(height - 1);  59.            int xl = random.nextInt(6) + 1;  60.            int yl = random.nextInt(12) + 1;  61.            g.drawLine(x,y,x + xl,y + yl);  62.        }  63.        for (int i = 0;i < 70;i++)  64.        {  65.            int x = random.nextInt(width - 1);  66.            int y = random.nextInt(height - 1);  67.            int xl = random.nextInt(12) + 1;  68.            int yl = random.nextInt(6) + 1;  69.            g.drawLine(x,y,x - xl,y - yl);  70.        }  71.  72.        String sRand="";  73.        for (int i=0;i<6;i++)  74.        {  75.   String tmp = getRandomChar();  76.            sRand += tmp;  77.            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));  78.         g.drawString(tmp,15*i+10,15);  79.        }  80.  81.        HttpSession session = request.getSession(true);  82.        session.setAttribute("rand",sRand);  83.        g.dispose();  84.        ImageIO.write(image, "JPEG", response.getOutputStream());  85.    }  86.    private String getRandomChar()  87.    {  88.  int rand = (int)Math.round(Math.random() * 2);  89.  long itmp = 0;  90.  char ctmp = '\u0000';  91.  switch (rand)  92.  {  93.   case 1:  94.    itmp = Math.round(Math.random() * 25 + 65);  95.    ctmp = (char)itmp;  96.    return String.valueOf(ctmp);  97.   case 2:  98.    itmp = Math.round(Math.random() * 25 + 97);  99.    ctmp = (char)itmp;  100.    return String.valueOf(ctmp);  101.   default :  102.    itmp = Math.round(Math.random() * 9);  103.    return String.valueOf(itmp);  104.  }  105.    }  106.}  

Step 3: Compile the login. jsp file with the following content:

01. <% @ page Language = "Java" Import = "Java. util. * "pageencoding =" gb18030 "%> 02. <% 03. string Path = request. getcontextpath (); 04. string basepath = request. getscheme () + ": //" + request. getservername () + ":" + request. getserverport () + path + "/"; 05. %> 06. 07. <! Doctype HTML public "-// W3C // dtd html 4.01 transitional // en"> 08. <HTML> 09. 
Step 4: configure the code in the web. xml file with the following content:

01.<servlet>  02.        <servlet-name>img</servlet-name>  03.        <servlet-class>check.check</servlet-class>  04.    </servlet>  05.  06.    <servlet-mapping>  07.        <servlet-name>img</servlet-name>  08.     <url-pattern>/check</url-pattern>  09.    </servlet-mapping>   
 
Step 5: Release the project check on the Tomcat server and run login. jsp. The running result is: