Bootstrap下拉菜单默认需要通过点击，才可以打开，在管理系统的开发过程中，使用悬停代替点击能减少一步操作，更人性化。下面是实现方式：
<!DOCTYPE html>
<html>
<head>
<link href="http://cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap.min.css" rel="stylesheet">
<script src="http://cdn.bootcss.com/jquery/2.1.4/jquery.js"></script>
<script src="http://cdn.bootcss.com/bootstrap/3.3.5/js/bootstrap.js"></script>
<script src="http://cdn.bootcss.com/bootstrap-hover-dropdown/2.0.10/bootstrap-hover-dropdown.min.js"></script>
</head>
<body>
<div class="dropdown">
<button type="button" class="btn dropdown-toggle" id="dropdownMenu1"
data-toggle="dropdown" data-hover="dropdown">
主题
<span class="caret"></span>
</button>
<ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1">
<li role="presentation">
<a role="menuitem" tabindex="-1" href="#">Java</a>
</li>
<li role="presentation">
<a role="menuitem" tabindex="-1" href="#">数据挖掘</a>
</li>
<li role="presentation">
<a role="menuitem" tabindex="-1" href="#">
数据通信/网络
</a>
</li>
<li role="presentation" class="divider"></li>
<li role="presentation">
<a role="menuitem" tabindex="-1" href="#">分离的链接</a>
</li>
</ul>
</div>
</body>
</html>
