以下哪些方法可以获取RequestDispatcher对象()(多选) A. RequestDispatcher dispatcher = request.getRequestDispatcher("/ResultServlet"); B. RequestDispatcher dispatcher =this.getServletContext().getRequestDispatcher("/ResultServlet"); C. RequestDispatcher dispatcher =this.getServletContext().getNamedDispatcher("/ResultServlet"); D. RequestDispatcher dispatcher = request.getServletContext().getRequestDispatcher("/ResultServlet");