/** 置session信息 */
 protected void setAttribute(String name, Object value) {
   JsfHelper.getSession(FacesContext.getCurrentInstance()).setAttribute(name, value);
 }
 /** 得到当前班级管理员 */
 protected Teacher getCurrentTeacher() {
   return (Teacher)
       JsfHelper.getSession(FacesContext.getCurrentInstance())
           .getAttribute(Contants.CLASS_TEACHER);
 }
 /** 得到session信息 */
 protected String getAttribute(String name) {
   return (String) JsfHelper.getSession(FacesContext.getCurrentInstance()).getAttribute(name);
 }
 protected HttpSession getSession() {
   return JsfHelper.getSession(FacesContext.getCurrentInstance());
 }