java 验证码的生成实现

Z时代
2024-01-10
分类：IT

java 验证码的生成实现

所谓验证码，就是将一串随机产生的数字或符号，生成一幅图片，图片里加上一些干扰，例如随机画数条直线或者画一些点，由用户肉眼识别其中的验证码信息，输入表单提交网站验证，验证成功后才能使用某项功能。验证码中之所以加上凌乱的直线是为了防止某些人使用OCR软件识别随机产生的数字或符号，从而达到恶意破解密码、刷票、论坛灌水、刷页等恶意行为。下面就开始直接上代码吧：

下面是Demo的文件组织结构

下面就是index.jsp的代码。主要功能是单击浏览器上的验证码图片，实现验证码的更换。


<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> 
<% 
String path = request.getContextPath(); 
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; 
%> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 
<html> 
 <head> 
  <base href="<%=basePath%>" rel="external nofollow" > 
  <title>验证码</title> 
  <meta http-equiv="pragma" content="no-cache"> 
  <meta http-equiv="cache-control" content="no-cache"> 
  <meta http-equiv="expires" content="0">   
  <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> 
  <meta http-equiv="description" content="This is my page"> 
  <title>验证码</title> 
  <script type="text/javascript"> 
  function refresh(obj) { 
    obj.src = "${pageContext.request.contextPath}/RandomValidateCodeServlet?"+Math.random(); 
  } 
  </script> 
 </head> 
 <body> 
  <form action="checkServlet" method="post"> 
    <img title="点击更换" onclick="javascript:refresh(this);" src="RandomValidateCodeServlet"> 
  </form> 
 </body> 
</html>

Web.xml中的servlet配置信息如下


<?xml version="1.0" encoding="UTF-8"?> 
<web-app version="2.5"  
  xmlns="http://java.sun.com/xml/ns/javaee"  
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee  
  http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> 
  <servlet> 
  <servlet-name>RandomValidateCodeServlet</servlet-name> 
  <servlet-class>com.web.RandomValidateCodeServlet</servlet-class> 
 </servlet> 
 <servlet-mapping> 
  <servlet-name>RandomValidateCodeServlet</servlet-name> 
  <url-pattern>/RandomValidateCodeServlet</url-pattern> 
 </servlet-mapping> 
 <welcome-file-list> 
  <welcome-file>index.jsp</welcome-file> 
 </welcome-file-list> 
</web-app>

下面是servlet中的代码,这里只是为了演示所以就只做了doGet方法，对于doPost方法就没有在这里考虑


public class RandomValidateCodeServlet extends HttpServlet { 
  public void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException { 
    response.setContentType("image/jpeg");//设置相应类型,告诉浏览器输出的内容为图片 
    response.setHeader("Pragma", "No-cache");//设置响应头信息，告诉浏览器不要缓存此内容 
    response.setHeader("Cache-Control", "no-cache"); 
    response.setDateHeader("Expire", 0); 
    RandomValidateCode randomValidateCode = new RandomValidateCode(); 
    try { 
      randomValidateCode.getRandcode(request, response);//输出图片方法 
    } catch (Exception e) { 
      e.printStackTrace(); 
    } 
  } 
}

下面就是验证码生成的主要类了


public class RandomValidateCode { 
  public static final String RANDOMCODEKEY = "RANDOMVALIDATECODEKEY";// 放到session中的key 
  private Random random = new Random(); 
  // 随机产生数字与字母组合的字符串 
  private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; 
  /* 
   * private String randString = "0123456789";//随机产生只有数字的字符串 private String 
   * randString = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生只有字母的字符串 
   */ 
  private int width = 80;// 图片宽 
  private int height = 26;// 图片高 
  private int lineSize = 40;// 干扰线数量 
  private int stringNum = 4;// 随机产生字符数量 
  /* 
   * 获得字体 
   */ 
  private Font getFont() { 
    return new Font("Fixedsys", Font.CENTER_BASELINE, 18); 
  } 
  /* 
   * 获得颜色 
   */ 
  private Color getRandColor(int fc, int bc) { 
    if (fc > 255) 
      fc = 255; 
    if (bc > 255) 
      bc = 255; 
    int r = fc + random.nextInt(bc - fc - 16); 
    int g = fc + random.nextInt(bc - fc - 14); 
    int b = fc + random.nextInt(bc - fc - 18); 
    return new Color(r, g, b); 
  } 
  /** 
   * 生成随机图片 
   */ 
  public void getRandcode(HttpServletRequest request, 
      HttpServletResponse response) { 
    HttpSession session = request.getSession(); 
    // BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类 
    BufferedImage image = new BufferedImage(width, height, 
        BufferedImage.TYPE_INT_BGR); 
    Graphics g = image.getGraphics();// 产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作 
    g.fillRect(0, 0, width, height); 
    g.setFont(new Font("Times New Roman", Font.ROMAN_BASELINE, 18)); 
    g.setColor(getRandColor(110, 133)); 
    // 绘制干扰线 
    for (int i = 0; i <= lineSize; i++) { 
      drowLine(g); 
    } 
    // 绘制随机字符 
    String randomString = ""; 
    for (int i = 1; i <= stringNum; i++) { 
      randomString = drowString(g, randomString, i); 
    } 
    //将生成的随机字符串保存到session中，而jsp界面通过session.getAttribute("RANDOMCODEKEY")， 
    //获得生成的验证码，然后跟用户输入的进行比较 
    session.removeAttribute(RANDOMCODEKEY); 
    session.setAttribute(RANDOMCODEKEY, randomString); 
    g.dispose(); 
    try { 
      // 将内存中的图片通过流动形式输出到客户端 
      ImageIO.write(image, "JPEG", response.getOutputStream()); 
    } catch (Exception e) { 
      e.printStackTrace(); 
    } 
  } 
  /* 
   * 绘制字符串 
   */ 
  private String drowString(Graphics g, String randomString, int i) { 
    g.setFont(getFont()); 
    g.setColor(new Color(random.nextInt(101), random.nextInt(111), random 
        .nextInt(121))); 
    String rand = String.valueOf(getRandomString(random.nextInt(randString 
        .length()))); 
    randomString += rand; 
    g.translate(random.nextInt(3), random.nextInt(3)); 
    g.drawString(rand, 13 * i, 16); 
    return randomString; 
  } 
  /* 
   * 绘制干扰线 
   */ 
  private void drowLine(Graphics g) { 
    int x = random.nextInt(width); 
    int y = random.nextInt(height); 
    int xl = random.nextInt(13); 
    int yl = random.nextInt(15); 
    g.drawLine(x, y, x + xl, y + yl); 
  } 
  /* 
   * 获取随机的字符 
   */ 
  public String getRandomString(int num) { 
    return String.valueOf(randString.charAt(num)); 
  } 
}