随机生成验证码

随机生成验证码 
login.jsp--------------------登录页面，在这里我是提供输入验证码然后提交进行验证
代码如下：


 <%   @ page contentType  =   "  text/html; charset=gb2312  "   %>  
  <  html  >  
  <  head  >  
  <  meta  http - equiv  = " Content-Type "   content  = " text/html; charset=gb2312 "   >  
  <  title  >  用户登录  </  title  >  
   <  script  language  = " javascript "   >   
    function  loadimage()    {
    document.getElementById(  "  randImage  "  ).src   =     "  image.jsp?  "   +  Math.random();
  }  
    </  script  >  
  </  head  >  
 
  <  body  >  
 
  <  table  width  = " 256 "   border  = " 0 "   cellpadding  = " 0 "   cellspacing  = " 0 "   >  
    <!--  DWLayoutTable  -->  
    <  form  action  = " validate.jsp "   method  = " post "   name  = " loginForm "   >  
    <  tr  >  
      <  td  width  = " 118 "   height  = " 22 "   valign  = " middle "   align  = " center "   ><  input  type  = " text "   name  = " rand "   size  = " 15 "   ></  td  >  
      <  td  width  = " 138 "   valign  = " middle "   align  = " center "   ><  img  alt  = " code "   name  = " randImage "   id  = " randImage "   src  = " image.jsp "   width  = " 60 "   height  = " 20 "   border  = " 1 "   align  = " absmiddle "   ></  td  >  
    </  tr  >  
    <  tr  >  
      <  td  height  = " 36 "   colspan  = " 2 "   align  = " center "   valign  = " middle "   ><  a  href  = " javascript:loadimage(); "   ><  font   class   = pt95  >  刷新  </  font  ></  a  ></  td  >  
    </  tr  >  
    <  tr  >  
      <  td  height  = " 36 "   colspan  = " 2 "   align  = " center "   valign  = " middle "   ><  input  type  = " submit "   name  = " login "   value  = " 提交 "   ></  td  >  
    </  tr  >  
    </  form  >  
  </  table  >  
  </  body  >  
  </  html  >  
 
 

image.jsp-------------------生成随即验证码图片的jsp页面
代码如下：


 <%   @ page contentType  =   "  image/jpeg  "    import   =   "  java.awt.*,  
  java.awt.image.  *  ,java.util.  *  ,javax.imageio.  *   "   %>  
   <   %! 
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);
} 
  %>  
   <%   
out.clear();  //  这句针对resin服务器，如果是tomacat可以不要这句 
 response.setHeader(  "  Pragma  "  ,  "  No-cache  "  );
response.setHeader(  "  Cache-Control  "  ,  "  no-cache  "  );
response.setDateHeader(  "  Expires  "  ,   0  );

  int   width  =   60  , height  =   20  ;
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(  0  ,   0  , width, height);

g.setFont(  new   Font(  "  Times New Roman  "  ,Font.PLAIN,  18  ));



g.setColor(getRandColor(  160  ,  200  ));
  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  );
g.drawLine(x,y,x  +  xl,y  +  yl);
} 
 
 
 String  sRand  =   ""  ;
  for   (  int   i  =   0  ;i  <   4  ;i  ++  )  {
 String  rand  =  String .valueOf(random.nextInt(  10  ));
sRand  +=  rand;

g.setColor(  new   Color(  20   +  random.nextInt(  110  ),  20   +  random.nextInt(  110  ),  20   +  random.nextInt(  110  )));
g.drawString(rand,  13   *  i  +   6  ,  16  );
} 
 
  //   将认证码存入SESSION 
 session.setAttribute(  "  rand  "  ,sRand);

g.dispose();

ImageIO.write(image,   "  JPEG  "  , response.getOutputStream());
  %>  
 

validate.jsp-------------用来验证输入的验证码是否正确
代码如下：

 <%   @ page contentType  =   "  text/html; charset=gb2312  "   %>  
   <%   
 String  rand   =   ( String )session.getAttribute(  "  rand  "  );
 String  input   =   request.getParameter(  "  rand  "  );
  if  (rand.equals(input))  {
out.print(  "  <script>alert('验证通过！');</script>  "  );
}    else    {
out.print(  "  <script>alert('请输入正确的验证码！');location.href='login.jsp';</script>  "  );
} 
  %>