jsp登陆的数字验证做法之一

在webcontent下的image/num中放入图片 num.rar   

jsp页面中代码是：

<td height="31" colspan="2" valign="top" class="STYLE15" ondragstart="return false" onselectstart="return false">
                                 验证码：
            <input name="yanzheng" type="text" class="input2"
                         onKeyDown="if(event.keyCode==13){form1.Submit.focus();}"
                                    size="8" align="bottom"
                                    onMouseOver="this.style.background='#F0DAF3';"
                                    onMouseOut="this.style.background='#FFFFFF'">

                                    <%
                                    int intmethod = (int)( (((Math.random())*11))-1);
                                    int intmethod2 = (int)( (((Math.random())*11))-1);
                                    int intmethod3 = (int)( (((Math.random())*11))-1);
                                    int intmethod4 = (int)( (((Math.random())*11))-1);
                                    String intsum = intmethod+""+intmethod2+intmethod3+intmethod4;
                                    //将得到的随机数进行连接

                                   %>
          <input type="hidden" name="verifycode2" value="<%=intsum%>">
                <span class="STYLE12"><font size="+3" color="#FF0000"><img src=Images/num/<%=intmethod %>.gif> <img src=Images/num/<%=intmethod2 %>.gif>

                    <img src=Images/num/<%=intmethod3%>.gif> <img src=Images/num/<%=intmethod4 %>.gif></font></span>
            </td>

jsp中的javascript对其先进行检查：

<script language="javascript">
 function mycheck(){
 if (form1.UserName.value=="")
 {alert("请输入用户名！");form1.UserName.focus();return;}
 if(form1.PWD.value=="")
 {alert("请输入密码！");form1.PWD.focus();return;}
 if(form1.yanzheng.value=="")
 {alert("请输入验证码!");form1.yanzheng.focus();return;}
 if(form1.yanzheng.value != form1.verifycode2.value)
 {alert("请输入正确的验证码!!");form1.yanzheng.focus();return;}
 form1.submit();
 }
 </script>