ServletContext概述和ServletContext获取&获取MIME类型

ServletContext对象

• 概念：代表整个web应用，可以和程序的容器（服务器）来通信
• 获取：
  • 通过request对象获取
    • request.getServletContext();
  • 通过HttpServlet获取
    • this.getServletContext();

package com.ailyt.servletContext;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/scs1")
public class ServletContextStudy01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        /**
         * ServletContext对象获取
         * 	* 通过request对象获取
         * 		* request.getServletContext();
         * 	* 通过HttpServlet获取
         * 		* this.getServletContext();
         */
        //通过request对象获取
        ServletContext context1 = req.getSession().getServletContext();
        //通过HttpServlet获取
        ServletContext context2 = this.getServletContext();
        System.out.println(context1);
        System.out.println(context2);

        System.out.println(context1 == context2);
    }
}

• 功能：
  • 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)：
  • 域对象：共享数据
  • 获取文件的真实（服务器）路径

package com.ailyt.servletContext;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet("/scs2")
public class ServletContextStudy02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        /**
         * ServletContext功能
         * 	 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)：
         */
        //通过request对象获取
        ServletContext context1 = req.getSession().getServletContext();

        //定义文件名称
        String fileName = "a.jpg";

        //获取MIME类型
        String mimeType = context1.getMimeType(fileName);
        System.out.println(mimeType);
    }
}