ServletContext对象一些功能

/*
            Sercletcontext对象获取
            1. 通过request对象获取
      request.getServletContext();
    2. 通过HttpServlet获取
      this.getServletContext();
         */
        ServletContext sc1 = request.getServletContext();
        ServletContext sc2 = this.getServletContext();
        System.out.println(sc1);
        System.out.println(sc2);
        System.out.println(sc1==sc1);

/*
            Sercletcontext对象功能
            1. 获取MIME类型：
      * MIME类型:在互联网通信过程中定义的一种文件数据类型
        * 格式： 大类型/小类型   text/html   image/jpeg
      * 获取：String getMimeType(String file)
         */
        //2.通过httpservlet获取
        ServletContext sc2 = this.getServletContext();
        //3.定义文件名称
        String filename = "a.jpg";//image/jpeg
        //4获取MIME类型：
        String mimeType = getServletContext().getMimeType(filename);
        System.out.println(mimeType);

/*
            Sercletcontext对象功能
           2. 域对象：共享数据
      1. setAttribute(String name,Object value)
      2. getAttribute(String name)
      3. removeAttribute(String name)
      * ServletContext对象范围：所有用户所有请求的数据
         */
        //2.通过httpservlet获取
        ServletContext bc = this.getServletContext();
        //设置数据
         bc.setAttribute("msg","haha");

//2.通过httpservlet获取
        ServletContext cd = this.getServletContext();
        //获取数据
        Object msg = cd.getAttribute("msg");
        System.out.println(msg);

//2.通过httpservlet获取
        ServletContext ct = this.getServletContext();
        //ServletContext cd = this.getServletContext();
        String s = ct.getRealPath("/WEB-INF/classes/a.txt");
        System.out.println(s);