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ServletContext

时间:2021-04-01 00:25:06      阅读:34      评论:0      收藏:0      [点我收藏+]

web容器在启动的时候,它会为每个web程序都创建一个对应的ServletContext对象,它代表了当前的web应用;

作用:

  1)共享数据,我在这个servlet中保存的数据,可以在另外一个servlet中拿到

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 HelloServlet

public class HelloServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        String username = "老尹";  // 数据
        context.setAttribute("username",username); // 将一个数据保存在ServletContext中
    }
}

getc

public class GetServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
// 获得ServletContext中放置的uaername数据,强转为String String username
= (String)context.getAttribute("username"); resp.setContentType("text/html"); // 设置文本格式 resp.setCharacterEncoding("utf-8"); // 设置字符格式 resp.getWriter().print("name" + username); // 输出信息到网页 } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp); } }

 

2) 获取初始化参数

<context-param>
  <param-name>url</param-name>
  <param-value>jdbc:mysql://localhost:3306/mybatis</param-value>
</context-param>
@Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        String url = context.getInitParameter("url");
        resp.getWriter().print(url);

    }

 

3)请求转发

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 gp的代码(gp是ServletDemo03的缩写)

package com.kuang.servlet;

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

public class ServletDemo03 extends HelloServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        String url = context.getInitParameter("url");
        resp.getWriter().print(url);

    }

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

 

图解重定向和转发:

重定向

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转发

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4:读取资源文件

Properties类

 

ServletContext

原文:https://www.cnblogs.com/YXBLOGXYY/p/14603432.html

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