JavaEE|ServletContext（运行环境信息） java|servlet

文章目录

一、 ServletContext
- 1.1 介绍
- 1.2 共享数据
- 1.3 获取初始化参数
- 1.4 请求转发
- 1.5 读取文件

学习视频来自于：秦疆（遇见狂神说）Bilibili地址
他的自学网站：kuangstudy

我们缺乏的不是知识，而是学而不厌的态度

一、 ServletContext 1.1 介绍 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；
1.2 共享数据我在ServletContextDemo1 保存数据，可以在ServletContextDemo2 中取出

public class ServletContextDemo1 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String data = "https://www.it610.com/article/xdp_gacl"; /** * ServletConfig对象中维护了ServletContext对象的引用，开发人员在编写servlet时， * 可以通过ServletConfig.getServletContext方法获得ServletContext对象。 */ ServletContext context = this.getServletConfig().getServletContext(); //获得ServletContext对象 context.setAttribute("data", data); //将data存储到ServletContext对象中 }public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }

public class ServletContextDemo2 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ServletContext context = this.getServletContext(); String data = https://www.it610.com/article/(String) context.getAttribute("data"); //从ServletContext对象中取出数据 response.getWriter().print("data="https://www.it610.com/article/+data); }public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }

1.3 获取初始化参数

username root

ServletContext context = this.getServletContext(); String username = context.getInitParameter("username"); resp.getWriter().println(username);

1.4 请求转发请求转发
浏览器地址栏不变
重定向
浏览器地址栏该表

RequestDispatcher requestDispatcher = context.getRequestDispatcher("/gp"); // 转发的路径 requestDispatcher.forward(req,resp); // 调用forward实现请求转发

1.5 读取文件 【JavaEE|ServletContext（运行环境信息）】使用Properties类

在resources目录下新建properties文件
配置文件被打包到了同一个路径下：classes，我们俗称这个路径为classpath:

@Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { ServletContext context = this.getServletContext(); InputStream is = context.getResourceAsStream("WEB-INF/classes/mysql.properties"); Properties pro = new Properties(); pro.load(is); String className = pro.getProperty("driverClassName"); resp.getWriter().println("driverClassName:"+className); }