Request共享数据以及获取ServletContext

Request共享数据

共享数据：

　　域对象：一个有作用范围的对象，可以在范围内共享数据

　　request域：代表一次请求

　　方法：

　　　　1、void setAttribute(String name,Object obj)：存储数据

　　　　2、Object getAttibute(String name)：通过键获取值

　　　　3、void removeAttribute(String name)：通过键移除键值对

 

@WebServlet("/requestDemo3")
public class RequestDemo3 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("requestDemo3.....");
        request.setAttribute("msg","hello");
        request.getRequestDispatcher("/requestDemo4").forward(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

 

@WebServlet("/requestDemo4")
public class RequestDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Object msg = request.getAttribute("msg");
        System.out.println(msg);
        System.out.println("requestDemo4.....");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

 

 

 

 

 

 

 

获取ServletContext

　　ServletContext  getServletContext();

@WebServlet("/requestDemo4")
public class RequestDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        ServletContext servletContext = request.getServletContext();
        System.out.println(servletContext);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}