渚漪Day13——JavaWeb 04【ServletContext】

2、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

1.共享数据

• 在一个Servlet中保存的数据，可以再另外一个Servlet中拿到

• 如图在打开ms之前姓名为空

• 开启ms后刷新，

• 示例代码：

public class myServletContext extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        String username = "鹿乃";
        context.setAttribute("username", username);
    }

}

public class ServletReceiver extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext context = this.getServletContext();
        String name = (String) context.getAttribute("username");

        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        resp.getWriter().println("姓名："+name);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

<servlet>
    <servlet-name>ms</servlet-name>
    <servlet-class>myServletContext</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>ms</servlet-name>
    <url-pattern>/ms</url-pattern>
</servlet-mapping>
<servlet>
    <servlet-name>s2</servlet-name>
    <servlet-class>ServletReceiver</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>s2</servlet-name>
    <url-pattern>/sr</url-pattern>
</servlet-mapping>

2.获取初始数据

context.getInitParameter("url");

3. 请求转发

context.getRequestDispatcher("/sr").forward(req, resp);

4.读取资源文件