package com.learn;

import javax.servlet.RequestDispatcher;
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;

/**
 * Created by Administrator on 2017/09/28.
 */
public class Check1Servlet extends HttpServlet {

 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

  String userName = req.getParameter("name");
  String message = "";

  if(userName == null){
   message = "please input your name";
  } else {
   message = userName;
  }
  req.setAttribute("mess",message);

  PrintWriter out = resp.getWriter();
  out.print("before redirect ");
  System.out.println("before redirect");

  resp.sendRedirect("out1?mess="+message);
  out.print("after redirect");
  System.out.println("after redirect");

  out.close();
 }
}

package com.learn;

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;

/**
 * Created by Administrator on 2017/09/28.
 */
public class Out1Servlet extends HttpServlet {

 @Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

  String mess = (String) req.getAttribute("mess");
  System.out.println("请求范围内的数据："+mess);

  mess = req.getParameter("mess");
  System.out.println("请求参数中的："+mess);

  PrintWriter out = resp.getWriter();
  out.write(mess);
  out.close();



 }
}