Java 随机生成验证码

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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>
 
 
 
 
 
 
 
 
 
 
 
 
 
 
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Date;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class ValidateCode
 */
@WebServlet("/ValidateCode")
public class ValidateCode extends HttpServlet {
    private static final long serialVersionUID = 1L;
        
    /**
     * @see HttpServlet#HttpServlet()
     */
    public ValidateCode() {
        super();
        // TODO Auto-generated constructor stub
    }
 
    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         
        // 设置页面不缓存
          response.setHeader("Pragma", "No-cache");
          response.setHeader("Cache-Control", "no-cache");
          response.setDateHeader("Expires", 0);
          // 设置图片的长宽
          int width = 62, height = 22;
          // ////// 创建内存图像
          BufferedImage image = new BufferedImage(width, height,
            BufferedImage.TYPE_INT_RGB);
          // 获取图形上下文
          Graphics g = image.createGraphics();
          // 设定图像背景色(因为是做背景，所以偏淡)
          g.setColor(getRandColor(180, 250));
          g.fillRect(0, 0, width, height);
          // 设置字体
          g.setFont(new Font("Times New Roman", Font.PLAIN, 17));
          // /////设置默认生成4个验证码
          int length = 4;
          java.util.Random rand = new Random(); // 设置随机种子
          /*
           * if (request.getParameter("length") != null) { try { length =
           * Integer.parseInt(request.getParameter("length")); }catch
           * (NumberFormatException e) {} }
           */
          // 设置备选验证码:包括"a-z"和数字"0-9"
          String base = "abcdefghijklmnopqrstuvwxyz0123456789";
          int size = base.length();
          StringBuffer str = new StringBuffer();
          for (int i = 0; i < length; i++) {
           int start = rand.nextInt(size);
           String tmpStr = base.substring(start, start + 1);
           str.append(tmpStr);
           // 生成随机颜色(因为是做前景，所以偏深)
           g.setColor(getRandColor(10, 150));
           // 将此字画到图片上
           // g.drawString(str.toString(), 4, 17);
           g.drawString(tmpStr, 13 * i + 6 + rand.nextInt(5), 14 + rand
             .nextInt(6));
          }
          // 将认证码存入session
          request.getSession().setAttribute("valiCode", str.toString());
          // 图象生效
          g.dispose();
          // 输出图象到页面
          ImageIO.write(image, "JPEG", response.getOutputStream());
         }
         public void doPost(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
          this.doGet(request, response);
         }
         // 给定范围获得一个随机颜色
         Color getRandColor(int fc, int bc) {
          Random random = new Random();
          if (fc > 255)
           fc = 255;
          if (bc > 255)
           bc = 255;
          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);
         }
        }
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