servletcontext

 Servletcontext是一种中间商 它可帮助两个类使用一个方法

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.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；

@Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //this.getInitParameter() 初始化参数
        //this.getServletConfig()  Servlet配文
        //this.getServletContext()
        ServletContext context=this.getServletContext();
        String  username="huaihuai";//数据
        context.setAttribute("username",username);//每一个数据保存在了ServletContext中，名字为username值为username
       resp.setContentType("text/html");
       resp.setCharacterEncoding("utf-8");
       resp.getWriter().print("名字"+username);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req,resp);
    }
}
测试结果

 

<!--    配置一些web应用初始化参数-->
    <context-param>
        <param-name>url</param-name>
        <param-value>jdbc:mysql://localhost:3386/mybatis</param-value>
    </context-param>

    <servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>com.zheng.servlet.HelloServlet/</servlet-class>
</servlet>
    <servlet-mapping>
        <servlet-name>hello</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>getc</servlet-name>
        <servlet-class>com.zheng.servlet.getservlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>getc</servlet-name>
        <url-pattern>/getc</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>fn</servlet-name>
        <servlet-class>com.zheng.servlet.ServletDome</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>fn</servlet-name>
        <url-pattern>/fn</url-pattern>
    </servlet-mapping>