select context and config

 

     

     @Override

     public void service(HttpServletRequest  request,HttpServletResponse response){

           //获取servletContext对象，写入数据，servletContext对象由服务器创建

            生命周期：服器启动到关闭

           ServletContext sc=this.getServletContext();//获取ServletContext对象

           sc.setAttribute("uname", "javaee");//写入数据

     

       

    @Override

    public void service(HttpServletRequest  request,HttpServletResponse response) {

           ServletContext sc=this.getServletContext();//获取对象  数据。

           String uname=(String) sc.getAttribute("uname");

           System.out.println(uname);

     }

     @Override

     public void service(HttpServletRequest  request,HttpServletResponse response) 

            //获取ServletConfig对象，获取Servlet的私有配置属性

           ServletConfig config=this.getServletConfig();

           String value=config.getInitParameter("charset");

           System.out.println(value);

     }

    //配置如下，使用<init-param>

    <servlet>

           <servlet-name>servlet11</servlet-name>

           <servlet-class>com.j2ee.ConfigServlet</servlet-class>

           <init-param>

                <param-name>charset</param-name>

                <param-value>utf-8</param-value>

           </init-param>

      </servlet>

       <servlet-mapping>

        <servlet-name>servlet11</servlet-name>

        <url-pattern>/config</url-pattern>

    </servlet-mapping>