为什么登录失败？代码和登录帐号密码都没问题啊

<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8" %>

<%

request.setCharacterEncoding("utf-8");

 %>

<%

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

String username="";

String password="";

request.setCharacterEncoding("utf-8");

//如果用户和密码都是admin，则登陆成功

if("admin".equals(username)&&"admin".equals(password))

{

request.getRequestDispatcher("login_success.jsp").forward(request,response);

}

else

{

response.sendRedirect("login_failure.jsp");

}

%>