Request数据可共享

共享数据

1. 域对象: 一个有作用范围的对象, 可以在范围内共享数据
2. request域: 代表一次请求的范围, 一般用于请求转发的多个资源中共享数据

方法:

1. setAttribute( String name , Object obj): 存储数据
2. Object getAttribute( String name ): 通过键获取
3. removeAttribute( String name) : 通过键移除键值对

代码示例

RequestDemo8项目

@WebServlet("/RequestDemo8")
public class RequestDemo8 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("demo8888被访问了.....");

        //存储数据到request域中
        request.setAttribute("msg","hello");


        //转发到demo9资源
        //通过 requestDispatcher 把 request 和 respond
        request.getRequestDispatcher("/RequestDemo9").forward(request, response);
    }

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

@WebServlet("/RequestDemo9")
public class RequestDemo9 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取数据
        Object msg = request.getAttribute("msg");
        System.out.println(msg);

        System.out.println("demo9999被访问了......");
    }

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