我要实现一个这样的登录方法不知道该怎样实现？请高手帮忙！

Question

<Script Language="JavaScript">
<%If session("username")="" Then%>
    window.open("c.html",c,"");
<%Else%>
    alert("username or password is invalid!");
    window.location = "a.html";
<%End If%>
</Script>

Answer 1

b.jsp
<%
HttpSession mysession=request.getSession(true);
String cUserName=(String)mysession.getValue("username");
if(cUserName==null)
{
%>
<script>
window.open("c.jsp","","");
</script>
<%
}
else
out.print("welcome");
%>c.jsp
<%
HttpSession mysession=request.getSession();
String username=request.getParameter("username");
String password=request.getParameter("password");
if(username!=null&&password!=null)
{
if(username.equals("ballack")&&password.equals("13"))
{
mysession.putValue("username",username);
%>
<script>
opener.location.reload(true);
window.close();
</script>
<%
}
}
%>
<form>
<input type=text name=username>
<input type=password name=password>
<input type=submit value=submit>
</form>