java Web中页面跳转方式之请求转发

1、在一个请求中跨越多个Servlet

2、多个Servlet在一个请求中，他们共享request对象。就是在Servlet01中setAttribute（）保存数据在Servlet02中由getAttribute（）取出数据

3、在Servlet01转发到Servlet02，那么整个请求都是由Servlet02来完成，Servlet01不再插手

4、Servlet01 包含Servlet02，那么两个Servlet共同完成请求

5、请求转发和请求包含都需要使用一个对象RequestDispatcher。

Servlet01:

public class DemoServlet01 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
    }
 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //从数据库获取数据
        UserService service = new UserService();
        List<User> userList = service.getUserList();
        //把数据放到request对象中
        request.setAttribute("userList", userList);
        //获取重定向对象
        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/DemoServlet03");
        //重定向对象执行操作
        requestDispatcher.forward(request, response);
    }
}

Servlet02:

public class DemoServlet02 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
    }
 
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //从request中取出数据
        List<User> list = (List<User>) request.getAttribute("userList");
        //响应到请求的客户端
        response.setContentType("text/html;charset=utf-8");
        for (User user : list) {
            response.getWriter().print(user);
        }
 
    }
}

附图一张:

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