Java实现随机验证码功能

小灰灰 2021-09-10 09:58 399阅读 0赞

<table style="width: 97%;"> 
 <tbody> 
 <tr> 
 <td align="center">来源：68design.net　2007年07月19日 08:58　<a href="http://www.68design.net/comment/20701-1.html" rel="nofollow">网友评论：0条</a>　点击：</td> 
 </tr> 
 <tr> 
 <td style="padding: 30px;"> 
 <div style="overflow: hidden; width: 610px;"> 
 现在许多系统的注册、登录或者发布信息模块都添加的随机码功能，就是为了避免自动注册程序或者自动发布程序的使用。 
 验证码实际上就是随机选择一些字符以图片的形式展现在页面上，如果进行提交操作的同时需要将图片上的字符同时提交，如果提交的字符与服务器session保存的不同，则认为提交信息无效。为了避免自动程序分析解析图片，通常会在图片上随机生成一些干扰线或者将字符进行扭曲，增加自动识别的难度。 
 在这里，我们使用servlet来实现随机验证码的实现。 
 package com.servlet; 
 import java.awt.Color; import java.awt.Font; import java.awt.Graphics2D; import java.awt.image.BufferedImage; 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 javax.servlet.http.HttpSession; 
 /** &nbsp;* 生成随机验证码 &nbsp;* @author bitiliu &nbsp;* &nbsp;*/ public class ValidateCodeServlet extends HttpServlet { 
 &nbsp;private static final long serialVersionUID = 1L; &nbsp; &nbsp;//验证码图片的宽度。 &nbsp;&nbsp;&nbsp; private int width=60; &nbsp;&nbsp;&nbsp; //验证码图片的高度。 &nbsp;&nbsp;&nbsp; private int height=20; &nbsp;&nbsp;&nbsp; //验证码字符个数 &nbsp;&nbsp;&nbsp; private int codeCount=4; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; private int x=0; &nbsp;&nbsp;&nbsp; //字体高度 &nbsp;&nbsp;&nbsp; private int fontHeight;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; private int codeY; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; char[] codeSequence = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', &nbsp;&nbsp; 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', &nbsp;&nbsp; 'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' }; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; /** &nbsp;&nbsp;&nbsp;&nbsp; * 初始化验证图片属性 &nbsp;&nbsp;&nbsp;&nbsp; */ &nbsp;&nbsp;&nbsp; public void init() throws ServletException &nbsp;{ &nbsp;&nbsp;&nbsp;&nbsp; //从web.xml中获取初始信息 &nbsp;&nbsp;&nbsp;&nbsp; //宽度 &nbsp; String strWidth=this.getInitParameter("width"); &nbsp; //高度 &nbsp; String strHeight=this.getInitParameter("height"); &nbsp; //字符个数 &nbsp; String strCodeCount=this.getInitParameter("codeCount"); &nbsp; &nbsp; //将配置的信息转换成数值 &nbsp; try &nbsp; { &nbsp;&nbsp; if(strWidth!=null &amp;&amp; strWidth.length()!=0) &nbsp;&nbsp; { &nbsp;&nbsp;&nbsp; width=Integer.parseInt(strWidth); &nbsp;&nbsp; } &nbsp;&nbsp; if(strHeight!=null &amp;&amp; strHeight.length()!=0) &nbsp;&nbsp; { &nbsp;&nbsp;&nbsp; height=Integer.parseInt(strHeight); &nbsp;&nbsp; } &nbsp;&nbsp; if(strCodeCount!=null &amp;&amp; strCodeCount.length()!=0) &nbsp;&nbsp; { &nbsp;&nbsp;&nbsp; codeCount=Integer.parseInt(strCodeCount); &nbsp;&nbsp; } &nbsp; } &nbsp; catch(NumberFormatException e) &nbsp; {} &nbsp; &nbsp; x=width/(codeCount+1); &nbsp; fontHeight=height-2; &nbsp; codeY=height-4; &nbsp; &nbsp;} &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; protected void service(HttpServletRequest req, HttpServletResponse resp) &nbsp;&nbsp; throws ServletException, java.io.IOException { &nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; //定义图像buffer &nbsp; BufferedImage buffImg = new BufferedImage( width, height,BufferedImage.TYPE_INT_RGB); &nbsp; Graphics2D g = buffImg.createGraphics(); 
 &nbsp; //创建一个随机数生成器类 &nbsp; Random random = new Random(); 
 &nbsp; //将图像填充为白色 &nbsp; g.setColor(Color.WHITE); &nbsp; g.fillRect(0, 0, width, height); 
 &nbsp; //创建字体，字体的大小应该根据图片的高度来定。 &nbsp; Font font = new Font("Fixedsys", Font.PLAIN, fontHeight); &nbsp; //设置字体。 &nbsp; g.setFont(font); 
 &nbsp; //画边框。 &nbsp; g.setColor(Color.BLACK); &nbsp; g.drawRect(0, 0, width - 1, height - 1); 
 &nbsp; //随机产生160条干扰线，使图象中的认证码不易被其它程序探测到。 &nbsp; g.setColor(Color.BLACK); &nbsp; for(int i = 0; i &lt; 160; i++) &nbsp; { &nbsp;&nbsp; int x = random.nextInt(width); &nbsp;&nbsp; int y = random.nextInt(height); &nbsp;&nbsp; int xl = random.nextInt(12); &nbsp;&nbsp; int yl = random.nextInt(12); &nbsp;&nbsp; g.drawLine(x, y, x + xl, y + yl); &nbsp; } 
 &nbsp; //randomCode用于保存随机产生的验证码，以便用户登录后进行验证。 &nbsp; StringBuffer randomCode = new StringBuffer(); &nbsp; int red = 0, green = 0, blue = 0; 
 &nbsp; //随机产生codeCount数字的验证码。 &nbsp; for (int i = 0; i &lt; codeCount; i++) { &nbsp;&nbsp; //得到随机产生的验证码数字。 &nbsp;&nbsp; String strRand = String.valueOf(codeSequence[random.nextInt(36)]); &nbsp;&nbsp; //产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同。 &nbsp;&nbsp; red = random.nextInt(255); &nbsp;&nbsp; green = random.nextInt(255); &nbsp;&nbsp; blue = random.nextInt(255); 
 &nbsp;&nbsp; //用随机产生的颜色将验证码绘制到图像中。 &nbsp;&nbsp; g.setColor(new Color(red, green, blue)); &nbsp;&nbsp; g.drawString(strRand, (i + 1) * x, codeY); 
 &nbsp;&nbsp; //将产生的四个随机数组合在一起。 &nbsp;&nbsp; randomCode.append(strRand); &nbsp; } &nbsp; // 将四位数字的验证码保存到Session中。 &nbsp; HttpSession session = req.getSession(); &nbsp; session.setAttribute("validateCode", randomCode.toString()); 
 &nbsp; // 禁止图像缓存。 &nbsp; resp.setHeader("Pragma", "no-cache"); &nbsp; resp.setHeader("Cache-Control", "no-cache"); &nbsp; resp.setDateHeader("Expires", 0); 
 &nbsp; resp.setContentType("image/jpeg"); 
 &nbsp; //将图像输出到Servlet输出流中。 &nbsp; ServletOutputStream sos = resp.getOutputStream(); &nbsp; <a rel="nofollow"></a>ImageIO.write(buffImg, "jpeg", sos); &nbsp; sos.close(); &nbsp;} 
 } 需要在web.xml中声明servlet 
 &lt;servlet&gt; &nbsp;&lt;servlet-name&gt;ValidateCodeServlet&lt;/servlet-name&gt; &nbsp;&lt;servlet-class&gt;com.servlet.ValidateCodeServlet&lt;/servlet-class&gt; &nbsp;&lt;init-param&gt; &nbsp; &lt;param-name&gt;width&lt;/param-name&gt; &nbsp; &lt;param-value&gt;200&lt;/param-value&gt; &nbsp;&lt;/init-param&gt; &nbsp;&lt;init-param&gt; &nbsp; &lt;param-name&gt;height&lt;/param-name&gt; &nbsp; &lt;param-value&gt;80&lt;/param-value&gt; &nbsp;&lt;/init-param&gt; &nbsp;&lt;init-param&gt; &nbsp; &lt;param-name&gt;codeCount&lt;/param-name&gt; &nbsp; &lt;param-value&gt;5&lt;/param-value&gt; &nbsp;&lt;/init-param&gt; &nbsp; &lt;/servlet&gt; 
 &nbsp; &lt;servlet-mapping&gt;&nbsp;&nbsp; &nbsp;&lt;servlet-name&gt;ValidateCodeServlet&lt;/servlet-name&gt;&nbsp;&nbsp; &nbsp;&lt;url-pattern&gt;/validateCodeServlet&lt;/url-pattern&gt;&nbsp;&nbsp; &nbsp; &lt;/servlet-mapping&gt; 需要引用的页面可以这样来写： 
 &lt;ccid_file values="validateCodeServlet" width="100/" /&gt; 用户提交后就可以将用户输入的验证码与session中保存的字符串进行比对，达到验证的效果。 
 </div> <a href="http://cache.baidu.com/c?m=9f65cb4a8c8507ed4fece763105392230e54f767368187542481cf5f93130716017b95ec63754e59919a2b3b47b2313d88ed3670320123a09bbe8b5dddccc86e70d633712d5cd04e498c4afa9c1d78d621e04de9d80ee6cab572c8e885c4df2544ba58120c8ae7fb591762cd&amp;p=8b2a950486cc42e000bb8c2650&amp;user=baidu" rel="nofollow">http://cache.baidu.com/c?m=9f65cb4a8c8507ed4fece763105392230e54f767368187542481cf5f93130716017b95ec63754e59919a2b3b47b2313d88ed3670320123a09bbe8b5dddccc86e70d633712d5cd04e498c4afa9c1d78d621e04de9d80ee6cab572c8e885c4df2544ba58120c8ae7fb591762cd&amp;p=8b2a950486cc42e000bb8c2650&amp;user=baidu</a></td> 
 </tr> 
 </tbody> 
</table>

\--------------------------------------------------------------------

public String getImg() throws IOException\{  
  String num=Verify.getNumber();  
  HttpSession session=request().getSession();  
  session.removeAttribute("validateCode");  
  session.setAttribute("validateCode",num);  
  BufferedImage image=Verify.display(response(),num);  
    
  response().reset();  
  response().setHeader("Pragma", "No-cache");  
  response().setHeader("Cache-Control", "no-cache");  
  response().setDateHeader("Expires", 0);  
  response().setContentType("image/jpeg");  
  OutputStream os = response().getOutputStream();  
  try \{  
    ImageIO.write(image, "JPEG", os);  
           
            
  \} catch (Exception e) \{  
   System.out.println("connection abort");  
   e.printStackTrace();  
  \}  
  finally\{  
   os.flush();  
   os.close();  
  \}  
  return NONE;  
 \}

\--------------------------------------验证验证码的对错-------------------、

private String validKey;  
 private String msg;

HttpSession session = ServletActionContext.getRequest().getSession();  
  String validCode = (String) session.getAttribute("validateCode");  
  session.setAttribute("validateCode", null);  
  if (!validKey.equalsIgnoreCase(validCode)) \{// 验证码不通过  
   msg = "验证码错误";  
   return "exchangeError";  
  \}