Someone

<%
                            String value =  request.getParameter("opcion");
                                if( value == null )
                                    opcion = 1;
                                else
                                    opcion =  Integer.parseInt( request.getParameter("opcion") );
                            
                            switch(opcion){
                                case 1: <%@ include file="administrador/crear.jsp" %>
                                        break;
                                case 2: <%@ include file="administrador/eliminar.jsp" %>
                                        break;
                                case 3: <%@ include file="administrador/modificar.jsp" %>
                                        break;
                                case 4: <%@ include file="administrador/visualizar.jsp" %>
                                        break;
                                case 5: salir;
                                        break;
                                default: opcion = 1;
                                        break;
                            }
                         %>