<c:choose> <c:when test="${!sessionScope.user eq null}"> <li><a href="#">${sessionScope.user.username}</a></li> <li><a href="loginOut">注销</a></li> </c:when> <c:otherwise> <li><a href="login">登录</a></li> <li><a href="regist">注册</a></li> </c:otherwise> </c:choose>