Java 随机生成验证码，支持大小写字母、数字、随机字体

java随机产生验证码，可以随机生成数字、大写字母、小写字母。还可以随机生成文字字体、及大小。在图片上面可能字体都不不同、大小不等。 
 
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> 验证码生成工具类
 * @project NetWorkService
 * @package com.hoo.util 
 * @fileName ValidCodeUtils.java
 * @createDate 2010-8-3 下午03:05:50
 * @author hoojo
 */ 
 @SuppressWarnings("unused") 
 public class ValidCodeUtils { 
 /*********************************************************************
  * 验证码宽度
  */ 
 public static int WIDTH = 60; 
 /***
  * 验证码高度
  */ 
 public static int HEIGHT = 20; 
  
 /**********************************************************************
  * 验证码背景颜色COLOR_FC_BG 应当小于COLOR_BC_BG
  */ 
 public static int COLOR_FC_BG = 200; 
 /***
  * 验证码背景颜色COLOR_FC_BG 应当小于COLOR_BC_BG
  */ 
 public static int COLOR_BC_BG = 250; 
  
 /**********************************************************************
  * 验证码背景干扰线颜色COLOR_FC_LINE 应当小于COLOR_BC_LINE
  */ 
 public static int COLOR_FC_LINE = 160; 
 /***
  * 验证码背景干扰线颜色COLOR_FC_LINE 应当小于COLOR_BC_LINE
  */ 
 public static int COLOR_BC_LINE = 200; 
  
 /***************************************************************************
  * 验证码颜色COLOR_FC_CODE 应当小于COLOR_BC_CODE
  */ 
 public static int COLOR_FC_CODE = 20; 
 /***
  * 验证码颜色COLOR_FC_CODE 应当小于COLOR_BC_CODE
  */ 
 public static int COLOR_BC_CODE = 170; 
  
 /***************************************************************************
  * 生成在指定范围内的颜色
  * @param fc 范围fc color值 小于255
  * @param bc 范围bc color值 小于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> 生成图片方法
  * @createDate 2010-8-3 下午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"); 
     // 设置页面不缓存 
     response.setHeader("Pragma", "No-cache"); 
     response.setHeader("Cache-Control", "no-cache"); 
     response.setDateHeader("Expires", 0); 
     // 在内存中创建图象      
     BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB); 
 
    // 获取图形上下文 
     Graphics img = image.getGraphics(); 
     // 生成随机类 
     Random random = new Random(); 
 
    // 设定背景色 
     img.setColor(getRandColor(COLOR_FC_BG, COLOR_BC_BG)); 
     img.fillRect(0, 0, WIDTH, HEIGHT); 
 
    // 设定字体 
     img.setFont(new Font("Times New Roman", Font.PLAIN, 18)); 
 
    // 画边框 
     // g.setColor(new Color()); 
     // g.drawRect(0,0,width-1,height-1); 
 
    // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到 
     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); 
     } 
 
    // 取随机产生的认证码(4位数字) 
     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());//随机字体 
  // 将认证码显示到图象中 
  img.setColor(getRandColor(COLOR_FC_CODE, COLOR_BC_CODE)); 
  img.drawString(rand, 13 * i + 6, 16); 
     } 
     request.getSession().setAttribute("codeValue", codeValue); 
     // 图象生效 
     img.dispose(); 
     // 输出图象到页面 
     return ImageIO.write(image, "JPEG", response.getOutputStream()); 
 } 
  
 /**
  * 随机生成字符，含大写、小写、数字
  * <b>function:</b> 功能
  * @createDate 2010-8-23 上午10:33:55
  * @author hoojo
  * @return
  */ 
 public static String getRandomChar() { 
     int index = (int) Math.round(Math.random() * 2); 
     String randChar = ""; 
     switch (index) { 
     case 0://大写字符 
  randChar = String.valueOf((char)Math.round(Math.random() * 25 + 65)); 
  break; 
     case 1://小写字符 
  randChar = String.valueOf((char)Math.round(Math.random() * 25 + 97)); 
  break; 
     default://数字 
  randChar = String.valueOf(Math.round(Math.random() * 9)); 
  break; 
     } 
     return randChar; 
 } 
  
 /**
  * <b>function:</b> 随机生成字体、文字大小
  * @createDate 2010-8-23 上午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); 
 } 
 } 
 
其中验证码的值是保存在session中：request.getSession().setAttribute("codeValue", codeValue);
 比较用户输入的值和session中的codeValue是否相等即可；
 
下面是jsp页面调用servlet：ValidCodeServlet.java
 
ValidCodeServlet中调用了上面的ValidCodeUtils 验证码生成工具类
 
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页面调用servlet方法即可
 
 
 
js：reloadValidCode方法 
 
function reloadValidCode(o) { 
 o.src = "${pageContext.request.contextPath }/validCodeServlet?timed=" + new Date().getMilliseconds(); 
 } 
 这里的"timed=" + new Date().getMilliseconds();是需要防止IE缓存用的 
 
html标签： 
 <img src="${pageContext.request.contextPath }/validCodeServlet" title="看不清，点击刷新" onclick="reloadValidCode(this)"/> 
 直接跟Servlet名称配置的url即可，和web.xml配置对应。主要调用路径${pageContext.request.contextPath }/validCodeServlet这样会带上根目录，比较保险。 
 
web.xml中validCodeServlet配置 
 <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>  

package cn.edu.bzu;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

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 com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class GetKey extends HttpServlet {
 //定义可选择的字符
 public static final char[] CHARS={'2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','J','K','L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z'};
 static Random random=new Random();
 
 public String getRandomString(){

  StringBuffer buffer=new StringBuffer();
  for(int i=0;i<6;i++){ //生成六个字符
   buffer.append(CHARS[random.nextInt(CHARS.length)]);
  }
  return buffer.toString();
 }
 
 public static Color getRandomColor(){  //得到随机颜色
  return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));  
 }
 
 public static Color getReverseColor(Color c){ //得到颜色的反色
  return new Color(255-c.getRed(),255-c.getGreen(),255-c.getBlue());
 }
 
 public void doGet (HttpServletRequest request,HttpServletResponse response)throws ServletException,IOException{
  response.setContentType("image/jpeg");  //设置输出类型
  String randomString=getRandomString();
  //将getSession（）设置为true，当会话不存在是返回null
  request.getSession(true).setAttribute("randomString",randomString);
  
  //设置图片的宽、高
  int width=100;
  int height=30;
  
  Color bcolor=getRandomColor(); //前景色
  Color fcolor=getReverseColor(getRandomColor()); //设置背景色
  
  //创建一个彩色图片
  BufferedImage bimage=new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR);
  //创建绘图对象
  Graphics2D g=bimage.createGraphics();
  //字体样式为宋体,加粗，20磅
  g.setFont(new Font("宋体",Font.BOLD,20));
  //先画出背景色
  g.setColor(bcolor);
  g.fillRect(0,0,width,height);
  //再画出前景色
  g.setColor(fcolor);
  //绘制随机字符
  g.drawString(randomString, 20,22);
  //画出干扰点
  for(int i=0,n=random.nextInt(100);i<n;i++){
   g.drawRect(random.nextInt(width), random.nextInt(height),1, 1);
  }
  
  ServletOutputStream outstream=response.getOutputStream();
  JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(outstream);
  
  encoder.encode(bimage);
  outstream.flush();


 }
}

 ====================================================
前台的JSP文件：
<%@ page language="java" contentType="text/html;charset=utf-8" %>
<%@ page import="cn.edu.bzu.GetKey" %>
<jsp:useBean id="show" scope="page" class="cn.edu.bzu.GetKey"/>
<html>
 <head><title>登陆</title>
 <script language="javascript" type="text/javascript">
  function changeImage(){
   document.getElementById("ch").disabled=true;
   document.getElementById("imc").src="http://localhost:8080/ExerciseTest/GetKey?ts="+newDate().getTime();
  }
 </script>
 </head>
 <body>
 <form action="GoTest" method="get">
  <table width="400" height="200" border="1" borderColor="blue">
   <tr>
     <td colspan="4" align="center">
    后台登陆
      </td>
   </tr>
   <tr>
    <td>用户名:</td>
    <td colspan="3"><input type="text" name="username" class="200px;height:30px;font-family:微软雅黑"/></td>
   </tr>
   <tr>
     <td>
       密&nbsp;&nbsp;码:
     </td>
     <td colspan="3">
     <input type="password" name="pass" class="200px;height:30px;"/>
     </td>
   </tr>
    <tr>
      <td>
       验证码:
      </td>
      <td>
       <input type="text" name="checkkey" class="80px;height:30px;padding-top:4px;"/>
      </td>
      <td>
      <img src="http://localhost:8080/ExerciseTest/GetKey" id="imc" onload="ch.disabled=false;"/>
      </td>
      <td>
     <a href="javascript:onclick=changeImage()" id="ch">看不清,换一张</a>
      </td>
    </tr>
   <tr>
     <td align="center" >