狂神说 javaweb 10集：ServletContext对象

10,ServletContext对象

6.5，ServletContext

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

• 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；

  设置类

   public class HelloServlet extends HttpServlet {
       @Override
       protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
   ​
           //this.getInitParameter();  初始化参数
           //this.getServletConfig();  Servlet配置
           //this.getServletContext();  Servlet上下文
           resp.setCharacterEncoding( "utf-8" );
   ​
           ServletContext context = this.getServletContext();
   ​
           String username = "test";
           context.setAttribute( "username",username ); //将一个数据保存在了ServletContext中，名字为：username 值为： username
   ​
           System.out.println("hello");
       }
   ​
       @Override
       protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
           doGet( req, resp );
       }
   }

  读取类

   public class GetServlet extends HttpServlet {
       @Override
       protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
           ServletContext context = this.getServletContext();
           String username = (String) context.getAttribute( "username" );
           resp.setContentType( "text/html" );
           resp.setCharacterEncoding( "utf-8" );
           resp.getWriter().print(username);
       }
   ​
       @Override
       protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
           doGet( req, resp );
       }
   }

  xml

   <servlet>
       <servlet-name>get</servlet-name>
       <servlet-class>com.study.GetServlet</servlet-class>
   </servlet>
   <servlet-mapping>
       <servlet-name>get</servlet-name>
       <url-pattern>/get</url-pattern>
   </servlet-mapping>

  测试访问结构：test

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