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ServletContext概述和ServletContext获取

ServletContext概述

概念：代表整个web应用，可以和程序的容器(服务器)来通信

功能：

　　1.获取MIME类型：

　　2.域对象：共享数据

　　3.获取文件的真实(服务器)路径

（代码解析）

ServletContext获取

1.通过request对象获取

　　request.getServletContext();

2.通过HTTPServlet获取

　　this.getServletContext();

@WebServlet("/servletContextD1")
public class ServletContextD1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        /*
        1.通过request对象获取
    　       　request.getServletContext();
        2.通过HTTPServlet获取
    　       　this.getServletContext();
         */
        //1.通过request对象获取
        ServletContext context1 = req.getServletContext();
        //2.通过HTTPServlet获取
        ServletContext context2 = this.getServletContext();
        System.out.println(context1);
        System.out.println(context2);
        System.out.println(context1==context2);

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}