JavaWeb-03-Servlet-12-多个Servlet之间的数据共享-03HttpServletRequest接口

1.介绍

1.在同一个网站中，如果两个Servlet之间通过【请求转发】方式进行调用，那么这两个Servlet之间共享的是同一个【请求协议包】。而一个请求协议包只对应一个请求对象，所以这两个Servlet共享的是同一个【请求对象】，利用这一点可以实现数据共享。

2.在请求对象实现Servlet之间数据共享功能时，开发人员将请求对象称为【请求作用域对象】

2.命令实现

OneServlet:

public class OneServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.将数据放入请求作用域对象的attribute属性中
        request.setAttribute("key1",数据【任意类型】);
        //2.向Tomcat申请调用TwoServlet
        request.getRequestDispatcher("/two").forward(request,response);
    }
}

TwoServlet:

public class TwoServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //从当前请求作用域对象中获取OneServlet写入的共享数据
        Object 存储数据变量 = request.getAttribute("key1");
    }
}

3.演示

OneServlet

package com.tsccg.controller;

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

/**
 * @Author: TSCCG
 * @Date: 2021/08/20 14:08
 */
public class OneServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.将数据放入请求作用域对象的attribute属性中
        request.setAttribute("name","张三");
        //2.向Tomcat申请调用TwoServlet
        request.getRequestDispatcher("/two").forward(request,response);
    }
}

TwoServlet:

package com.tsccg.controller;

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

/**
 * @Author: TSCCG
 * @Date: 2021/08/20 14:12
 */
public class TwoServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //从当前请求作用域对象中获取OneServlet写入的共享数据
        String name = (String)request.getAttribute("name");
        response.setContentType("text/html;charset=utf-8");
        PrintWriter out = response.getWriter();
        out.print("<center><font style=‘color:red;font-size:30px‘>TwoServlet得到了共享数据："+ name +"</font></center>");
    }
}

打开浏览器访问OneServlet:

JavaWeb-03-Servlet-12-多个Servlet之间的数据共享-03HttpServletRequest接口