Java randomly generates instances of the captcha of that support uppercase and lowercase letters Numbers and random fonts

The 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>  Captcha generation utility class 
 * @project NetWorkService
 * @package com.hoo.util 
 * @fileName ValidCodeUtils.java
 * @createDate 2010-8-3  In the afternoon 03:05:50
 * @author hoojo
 */ 
 @SuppressWarnings("unused") 
 public class ValidCodeUtils { 
  
 public static int WIDTH = 60; 
  
 public static int HEIGHT = 20; 

  
 public static int COLOR_FC_BG = 200; 
  
 public static int COLOR_BC_BG = 250; 

  
 public static int COLOR_FC_LINE = 160; 
  
 public static int COLOR_BC_LINE = 200; 

  
 public static int COLOR_FC_CODE = 20; 
  
 public static int COLOR_BC_CODE = 170; 

  
 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 2010-8-3  In the afternoon 03:06:22
  * @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 be cached
     response.setHeader("Pragma", "No-cache"); 
     response.setHeader("Cache-Control", "no-cache"); 
     response.setDateHeader("Expires", 0); 
     //Creating an image in memory & NBSP;        
     BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB); 

    //Getting the graphics context
     Graphics img = image.getGraphics(); 
     //Generate random class
     Random random = new Random(); 

    //Setting 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)); 

    //Picture frame
     // g.setColor(new Color()); 
     // g.drawRect(0,0,width-1,height-1); 

    //Randomly generated 155 interference lines, so that the authentication code in the image is not easy 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); 
     } 

    //Take the randomly generated authentication 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
  //Displays the authentication code in 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 effect
     img.dispose(); 
     //Output image to page
     return ImageIO.write(image, "JPEG", response.getOutputStream()); 
 } 

 /**
  *  Randomly generated characters, including uppercase, lowercase, and number 
  * <b>function:</b>  function 
  * @createDate 2010-8-23  In the morning 10:33:55
  * @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://digital
  randChar = String.valueOf(Math.round(Math.random() * 9)); 
  break; 
     } 
     return randChar; 
 } 

 /**
  * <b>function:</b>  Randomly generate font, text size 
  * @createDate 2010-8-23  In the morning 10:44:22
  * @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); 
 } 
 } 

 Where the value of the captcha is saved in session In: request.getSession().setAttribute("codeValue", codeValue);
  Compare the values entered by the user to session In the codeValue Equal or not; 

 The following is jsp Page calls servlet : ValidCodeServlet.java

ValidCodeServlet The above is called in ValidCodeUtils  Captcha generation utility 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); 
 } 
 } 

 

jsp Page calls servlet Methods can be 

 

js : reloadValidCode methods  

function reloadValidCode(o) { 
 o.src = "${pageContext.request.contextPath }/validCodeServlet?timed=" + new Date().getMilliseconds(); 
 } 
  Here, "timed=" + new Date().getMilliseconds(); Is to prevent IE Cache with  

html Tags:  
 <img src="${pageContext.request.contextPath }/validCodeServlet" title=" It's hard to see. Hit refresh " onclick="reloadValidCode(this)"/> 
  Directly with Servlet name-configured url Can, and web.xml Configure the correspondence. Main invocation path ${pageContext.request.contextPath }/validCodeServlet This will bring the root directory, more safe.  

web.xml In the validCodeServlet configuration  
 <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>