HttpServletResponse概述

response的运行流程

response：

1. 属于重定向请求；

2. 其地址栏的URL会改变；

3.会向服务器发送两次请求；

用response，A没有钱，请求失败，但是A告诉B，C有钱。于是B再次向C借钱，C借给B，请求成功。

response是响应对象。

通过response设置响应行

设置响应行的状态码

setStatus(int sc)

package com.oracle.demo01;

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

public class HeadServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//设置响应行中的状态码(只能改变响应行中的状态码，版本号与状态信息无法改变，状态信息随着状态的改变而改变)
		response.setStatus(404);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
}

通过response设置响应头

有众多方法，但是常用的就是setHeader(String name,String value)

重定向需要：1.状态码：302

　　　　　　2.响应头：location 代表重定向地址

使用该方法设置的响应头最终会发送给客户端浏览器

package com.oracle.demo01;

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

import com.sun.org.apache.regexp.internal.RESyntaxException;

public class Servlet01 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
/*		//设置响应行状态码
		response.setStatus(302);
	    　　//设置响应头中的Location
		response.setHeader("Location","/WEB05/Servlet02");*/
		//重定向(与上面的代码是一致的)简洁版
		response.sendRedirect("/WEB05/Servlet02");
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
}

设置定时刷新响应头的信息

package com.oracle.demo01;

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

public class RefreshServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//设置定时刷新的头
		response.setHeader("Refresh","5;url=https://www.baidu.com");
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
}

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
 window.onload=function(){
	 //获取span元素
	 var second=document.getElementById("second");
	 //定义秒数
	 var time=5;
	 //设置定时器
	 var timer=setInterval(function(){
		 second.innerHTML=time;
		 time--;
		 if(time<0){
			 clearInterval(timer);
			 location.href="https://www.baidu.com";
		 }
	 },1000);
 }
</script>
</head>
<body>
  	 恭喜你，注册成功！
  	 <span id="second" style="color:red">5</span>
  	 秒后跳转，如没跳转，请点击
  	 <a href="https://www.baidu.com">这里</a>
</body>
</html>

通过response设置响应体

解决中文乱码问题

需要设置两个地方的中文乱码问题，一个是缓冲区的时候设置，一个是客户端解码的时候进行设置。

package com.oracle.demo01;

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

public class BodyServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		/*//设置缓冲区的编码表
		response.setCharacterEncoding("UTF-8");
		//设置客户端浏览器
		response.setHeader("Content-Type","text/html;charset=utf-8");*/
		//解决响应的中文乱码问题(与上面的代码是一样的，简洁版)
		response.setContentType("text/html;charset=utf-8");
		response.getWriter().write("中国");
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request, response);
	}
}