请求转发与请求作用域

创建input.jsp页面，通过表单输入学号、姓名后，单击登录按钮，控制转发到FirstServlet对其进行处理，然后通过请求对象的getRequestDispartcher()获得RequestDispartcher对象，将请求转发至SecondServlet，在SecondServlet中用输出流对象out输出该学生的学号和姓名。输出页面还包含一个超链接，单击该链接可以返回至input.jsp页面。

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
login.jsp
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><base href="<%=basePath%>"><title>ForwordJsp.jsp</title><meta http-equiv="description" content="This is my page" chartset="utf-8"></head><body>this is students form: <br><form action="FirstServlet.do" >学号:<input name="id" value=" "><br><br>姓名:<input name="name" value=" "><br><br><a> &nbsp;&nbsp;&nbsp;</a><button type="submit">登录</button>  <a> &nbsp;&nbsp;&nbsp;&nbsp;</a><button type="reset" >取消</button></form></body>
</html>

package com.demo;import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import java.util.regex.Pattern;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;@WebServlet("/getMethod")
public class SecondServlet extends HttpServlet {private static final long serialVersionUID = 1L;public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType("text/html;charset=utf-8");PrintWriter out = response.getWriter();Student stu  = (Student) request.getAttribute("stu");String id = stu.getId();String name = stu.getName();out.println("<!DOCTYPE>");out.println("<HTML>");out.println("  <HEAD><TITLE>result</TITLE></HEAD>");out.println("  <BODY>");out.print(" 学号: "+id + "<br> ");out.print(" 姓名: "+name + "<br> ");out.print("<div><a href=\"http://localhost:8080/demo/login.jsp\">返回输入首页 </a></div>");out.println("  </BODY>");out.println("</HTML>");out.flush();out.close();}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doGet(request, response);}
}

package com.demo;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import java.util.List;
import javax.json.Json;
import javax.json.JsonArray;
import javax.json.JsonObject;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
@WebServlet("/login")
public class FirstServlet extends HttpServlet {private static final long serialVersionUID = 1L;public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType("text/html;charset=UTF-8");PrintWriter out = response.getWriter();String id = request.getParameter("id");String name = request.getParameter("name");	request.setAttribute("stu",new Student(id, name));System.out.println("成功 == "+ id +"  ==  "+name);    request.getRequestDispatcher("/SecondServlet.do").forward(request, response);out.flush();out.close();}
}