request实现请求重定向和request的一些细节

package cn.itcast.response;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

//实现请求重定向

/*

* 重定向的特点：

* 1.浏览器会向服务器发送2次，意味着就有2个request、response

* 2.用重定向技术，浏览器地址会发生变化

*

* 用户登陆和显示购物车时，通常会用到重定向

*/

public class ResponseDemo7 extends HttpServlet {

//同时调用getOutputStream和getWriter方法会抛java.lang.IllegalStateException: getOutputStream() has already been called for this response

public void doGet(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

//要对http协议很熟悉

// response.setStatus(302);

// response.setHeader("location", "/day06/index.jsp");

//response.sendRedirect("/day06/index.jsp");

response.getOutputStream();

this.getServletContext().getRequestDispatcher("/ResponseDemo8").forward(request, response);

}

public void doPost(HttpServletRequest request, HttpServletResponse response)

throws ServletException, IOException {

doGet(request, response);

}

}