<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<link rel="stylesheet" type="text/css" href="<%= basePath %>bootstrap/css/bootstrap.min.css">
</head>
<body>
This is my JSP page. <br>
<div class="dropdown">
<button class="btn btn-default dropdown-toggle" data-toggle="dropdown" >hello<span class="caret"></span></button>
<ul class="dropdown-menu"><li><a href="#">哈哈</a></li><li><a href="#">哈哈</a></li></ul>
</div>
<script src="<%= basePath %>js/jquery-3.1.1.min.js"></script>
<script src="<%= basePath %>bootstrap/js/bootstrap.min.js"></script>
</body>
</html>
bootstrap用的是3.3.7
代码没错，稳一点把<%= basePath %>改成你的路径，<meta charset="utf-8" />加一下。代码上没问题，只有路径的可能性错误