Request-共享数据(域对象)、获取ServletContext

Request共享数据(域对象)

 共享数据：

　　　　域对象：一个有作用范围的对象，可以在范围内共享数据

　　　　request域：代表一次请求的范围，一般用于请求转发的多个资源中共享数据

　　方法：

　　　　void setAttribute(String name,Object obj):存储数据

　　　　Object getAttitude(String name):通过键获取值

　　　　void removeAttribute(String name):通过键移除键值对

Request获取ServletContext

　　获取ServletContext

　　　　ServletContext getServletContext()

package com.example.request;

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("/requestDemo10")
public class RequestDemo10 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


        ServletContext servletContext = request.getServletContext();

        System.out.println(servletContext);

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        this.doPost(request,response);
    }
}