servlet/jsp 获取绝对路径和相对路径

根目录所对应的绝对路径:request.getServletPath();

文件的绝对路径 :request.getSession().getServletContext().getRealPath(request.getRequestURI())

当前web应用的绝对路径 :servletConfig.getServletContext().getRealPath("/");

ServletContext对象获得几种方式：

Javax.servlet.http.HttpSession.getServletContext()

Javax.servlet.jsp.PageContext.getServletContext()

Javax.servlet.ServletConfig.getServletContext()