Request_请求转发和Request_共享数据(域对象)

请求转发：一种再服务器内部的资源跳转方式

• 步骤：
  • 通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)
  • 使用RequestDispatcher对象来进行转发：forward(ServletRequest request,ServletResponse response)
• 特点：
  • 浏览器地址栏路径没有发生变化
  • 只能转发到当前服务器内部资源中
  • 转发是一次请求

package com.ailyt.request;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Map;

@WebServlet(value = "/r5")
public class RequestStudy5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }



    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("r5.......................");
        //转发到r9资源
        /*RequestDispatcher requestDispatcher = req.getRequestDispatcher("/r6");
        requestDispatcher.forward(req,resp);*/
        req.getRequestDispatcher("/r6").forward(req,resp);
    }
}

package com.ailyt.request;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(value = "/r6")
public class RequestStudy6 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        this.doPost(req,resp);
    }



    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("r6................");
    }
}

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：代表一次请求的范围，一般用于请求转发的多个资源中共享数据
• 方法：
  • setAttribute(String name，Object obj)：存储数据
  • Object getAttribute(String name)：通过键获取值
  • removeAttribute(String name)：通过键移除键值对

package com.ailyt.request;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(value = "/r6")
public class RequestStudy6 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }



    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取数据
        Object msg = req.getAttribute("msg");
        System.out.println(msg);
        System.out.println("r6................");

    }
}

package com.ailyt.request;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Map;

@WebServlet(value = "/r5")
public class RequestStudy5 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }



    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("r5.......................");
        //转发到r9资源
        /*RequestDispatcher requestDispatcher = req.getRequestDispatcher("/r6");
        requestDispatcher.forward(req,resp);*/

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

        req.getRequestDispatcher("/r6").forward(req,resp);
    }
}