通俗的讲，有/会从跟目录开始算，没有会从当前目录开始算
1.前台页面
页面中向服务器页面请求静态资源且没有指定<base href="<%=basePath%>">
访问以下页面
localhost:8080/resolvent/index.jsp
localhost:8080/resolvent/servlet/dnf
有/的
跟目录是域名+端口号(localhost:8080)
请求以下资源
<script type="text/css" src=''/demo.js"></script>
最终浏览器发送的请求都是localhost:8080/demo.js
没有/
<script type="text/css" src=''demo.js"></script>
localhost:8080/resolvent/demo.js 当前目录localhost:8080/resolvent/
localhost:8080/resolvent/servlet/demo.js 当前目录 localhost:8080/resolvent/servlet/
2.后台代码
请求转发，请求重定向，已以下两个url为例
localhost:8080/resolvent/servlet/dnf
localhost:8080/resolvent/index.jsp
有/的
根目录是(localhost:8080/resolvent)
request.getRequestDispatcher("/login.jsp").forward(request,response);
最后都会定位到
localhost:8080/resolvent/login.jsp
没有/
request.getRequestDispatcher("login.jsp").forward(request,response);
localhost:8080/resolvent/servlet/login.jsp 当前目录localhost:8080/resolvent/servlet/
localhost:8080/resolvent/login.jsp 当前目录localhost:8080/resolvent/