在servlet写了个跳转话语不能执行

在servlet写了个跳转语句不能执行

public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html");
		UserDao ud=new UserDao();
		String username=request.getParameter("user");
		String userpassword=request.getParameter("pwd");
		boolean flag=ud.sel(username);
		System.out.println(username);
		System.out.println(userpassword);
		System.out.println(flag);
		PrintWriter out = response.getWriter();
		if(flag){
			out.print("The user name has been registered!");
		}else{
			out.print("<script>window.location.href='login.jsp';</script>");
			//response.sendRedirect("login.jsp");
		}
	}

用out.print("<script>window.location.href='login.jsp';</script>");显示

用response.sendRedirect("login.jsp");这个显示

------解决方案--------------------
试试这个：

if(flag){
            out.print("The user name has been registered!");
        }else{
            //out.print("<script>window.location.href='login.jsp';</script>");
            response.sendRedirect("login.jsp");
        }