RequestDispatcher 为什么总找不到？

[albertlee]

我用Servlet写一个前端控制器，编译时说 RequestDispatcher找不到？为什么？
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class AdminController extends HttpServlet
{
public void init(ServletConfig config)throws ServletException
{
super.init(config);
}
public void destroy()
{
}

public void doGet(HttpServletRequest req,HttpServletResponse res)
throws ServletException,IOException
{
// dispatch(req,res,"/admin/login.jsp");
}


public String getServletInfo()
{
return "Admin 前端控制器";
}
protected void dispatch(HttpServletRequest request,
HttpServletResponse response,
String page)
throws ServletException,IOException
{
// RequestDispatcher dispatcher=getServletContext().getRequestDispatcher(page);
// dispatcher.forward(request,response);
}
}