验证码代码发布

 验证码是什么?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象素(防止OCR),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的一种工具吧。。

验证码一般是防止有人利用机器人自动批量注册、对特定的注册用户用特定程序暴力破解方式进行不断的登陆、灌水。因为验证码是一个混合了数字或符号的图片,人眼看起来都费劲,机器识别起来就更困难。 一般注册用户ID的地方以及各大论坛都要要输入验证码。

 

 

 


例: 1.VerifyCodeServlet.java public class VerifyCodeServlet extends HttpServlet    {        private static final String CONTENT_TYPE  = "text/html; charset=gb2312";       //设置字母的大小,大小       private Font mFont = new Font ("Times New Roman", Font.PLAIN, 17);       public void init() throws ServletException       {     super.init();       }       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);       }        public void service(HttpServletRequest request,  HttpServletResponse response)  throws ServletException, IOException       {     response.setHeader("Pragma","No-cache");     response.setHeader("Cache-Control","no-cache");     response.setDateHeader("Expires", 0);     //表明生成的响应是图片     response.setContentType("image/jpeg");          int width=100, height=18;     BufferedImage image = new BufferedImage (width, height, BufferedImage.TYPE_INT_RGB);          Graphics g = image.getGraphics();     Random random = new Random();     g.setColor(getRandColor(200,250));     g.fillRect(1, 1, width-1, height-1);     g.setColor(new Color(102,102,102));     g.drawRect(0, 0, width-1, height-1);     g.setFont(mFont);      g.setColor(getRandColor(160,200));//画随机线 

for (int i=0;i<155;i++)   
 {   
    int x = random.nextInt(width - 1);   
    int y = random.nextInt(height - 1);   
    int xl = random.nextInt(6) + 1;   
    int yl = random.nextInt(12) + 1;   
    g.drawLine(x,y,x + xl,y + yl);   
 }   

 //从另一方向画随机线   
 for (int i = 0;i < 70;i++)   
 {   
    int x = random.nextInt(width - 1);   
    int y = random.nextInt(height - 1);   
    int xl = random.nextInt(12) + 1;   
    int yl = random.nextInt(6) + 1;   
    g.drawLine(x,y,x - xl,y - yl);   
 }   

 //生成随机数,并将随机数字转换为字母   
 String sRand="";   
 for (int i=0;i<6;i++)   
 {   
    int itmp = random.nextInt(26) + 65;   
    char ctmp = (char)itmp;   
    sRand += String.valueOf(ctmp);   
    g.setColor(new Color(20+random.nextInt(110),
20+random.nextInt(110),20+random.nextInt(110)));   
    g.drawString(String.valueOf(ctmp),15*i+10,16);   
 }   

 HttpSession session = request.getSession(true);   
 session.setAttribute("rand",sRand);   
 g.dispose();   
 ImageIO.write(image, "JPEG", response.getOutputStream());   
   }   
   public void destroy()   
   {   
   }   
}    
 
2.web.xml
<servlet>
   <servlet-name>verifyCodeServlet</servlet-name>
   <servlet-class>com.yangfei.test.servlet.VerifyCodeServlet</servlet-class>
</servlet>

<servlet-mapping>
   <servlet-name>verifyCodeServlet</servlet-name>
<url-pattern>/verifyCodeServlet</url-pattern>
</servlet-mapping>
 
3.页面:
<img src="verifyCodeServlet">

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