1．HttpServletResponse概述

我们在创建Servlet时会覆盖service()方法，或doGet()/doPost(),这些方法都有两个参数，一个为代表请求的request和代表响应response。

service方法中的response的类型是ServletResponse，而doGet/doPost方法的response的类型是HttpServletResponse，HttpServletResponse是ServletResponse的子接口，功能和方法更加强大。

2．response的运行流程

response响应码怎么获取 response获取响应内容_状态码

3．通过抓包工具抓取Http响应

response响应码怎么获取 response获取响应内容_response响应码怎么获取_02

因为response代表响应，所以我们可以通过该对象分别设置Http响应的响应行，响 应头和响应体

4．通过response设置响应行

设置响应行的状态码

setStatus(int sc)

该方法用于设置HTTP响应消息的状态码，并生成响应行。由于响应状态行中的状态描述信息直接与状态码相关，而HTTP版本由服务器确定，因此，只要通过setStatus(int status)方法设置了状态码，即可实现状态行的发送，需要注意的是，正常情况下，Web服务器会默认产生一个状态码为200的状态行。

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 StatusServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		//手动设置http响应行中的状态码
		response.setStatus(404);
		
	}

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

5．通过response设置响应头
addHeader(String name, String value)
addIntHeader(String name, int value)
addDateHeader(String name, long date)
setHeader(String name, String value)
setDateHeader(String name, long date)
setIntHeader(String name, int value)
其中，add表示添加，而set表示设置

import java.io.IOException;
import java.util.Date;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HeaderServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		Date date = new Date();
		
		//设置响应头
		response.addHeader("name", "zhangsan");
		//response.addIntHeader("age", 28);
		//response.addDateHeader("birthday", date.getTime());
		
		response.addHeader("name", "lisi");
		
		response.setHeader("age", "28");
		response.setHeader("age", "50");
		
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}
}
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 Servlet1 extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		//没有响应 告知客户端去重定向到servlet2
		//1、设置状态码302
		//response.setStatus(302);
		//2、设置响应头Location
		//response.setHeader("Location", "/WEB14/servlet2");
		
		//封装成一个重定向的方法sendRedirect(url)
		response.sendRedirect("/WEB14/servlet2");
		
	}

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

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

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

6．通过response设置响应体
(1)响应体设置文本
PrintWriter getWriter()
获得字符流，通过字符流的write(String s)方法可以将字符串设置到response缓冲区中，随后Tomcat会将response缓冲区中的内容组装成Http响应返回给浏览器端。

关于设置中文的乱码问题
原因：response缓冲区的默认编码是iso8859-1，此码表中没有中文，可以通过response的setCharacterEncoding(String charset) 设置response的编码。

但我们发现客户端还是不能正常显示文字
原因：我们将response缓冲区的编码设置成UTF-8，但浏览器的默认编码是本地系统的编码，因为我们都是中文系统，所以客户端浏览器的默认编码是GBK，我们可以手动修改浏览器的编码是UTF-8。

我们还可以在代码中指定浏览器解析页面的编码方式
通过response的setContentType(String type)方法指定页面解析时的编码是UTF-8
response.setContentType(“text/html;charset=UTF-8”)
上面的代码不仅可以指定浏览器解析页面时的编码，同时也内含 setCharacterEncoding的功能，所以在实际开发中只要编写 response.setContentType(“text/html;charset=UTF-8”)

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;

public class TextServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		//设置response查询的码表
		//response.setCharacterEncoding("UTF-8");
		
		//通过一个头 Content-Type 告知客户端使用何种码表
		//response.setHeader("Content-Type", "text/html;charset=UTF-8");
		
		response.setContentType("text/html;charset=UTF-8");
		
		PrintWriter writer = response.getWriter();
		//writer.write("hello response!!!");
		writer.write("你好");
		
	}

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

(2)响应头设置字节输出
ServletOutputStream getOutputStream()
获得字节流，通过该字节流的write(byte[] bytes)可以向response缓冲区中写入字节，在由Tomcat服务器将字节内容组成Http响应返回给浏览器。

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ByteServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		//使用response获得字节输出流
		ServletOutputStream out = response.getOutputStream();
		
		//获得服务器上的图片
		String realPath = this.getServletContext().getRealPath("a.jpg");
		InputStream in = new FileInputStream(realPath);
		
		int len = 0;
		byte[] buffer = new byte[1024];
		while((len=in.read(buffer))>0){
			out.write(buffer, 0, len);
		}
		
		in.close();
		out.close();
		
	}

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

7．案例-完成文件下载
文件下载的实质就是文件拷贝，将文件从服务器端拷贝到浏览器端。所以文件下载需要IO技术将服务器端的文件使用InputStream读取到，在使用ServletOutputStream写到response缓冲区中

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DownloadServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		//获得要下载的文件的名称
		String filename = request.getParameter("filename");//a.flv

		//要下载的这个文件的类型-----客户端通过文件的MIME类型去区分类型
		response.setContentType(this.getServletContext().getMimeType(filename));
		//告诉客户端该文件不是直接解析 而是以附件形式打开(下载)
		response.setHeader("Content-Disposition", "attachment;filename="+filename);

		//获取文件的绝对路径
		String path = this.getServletContext().getRealPath("download/"+filename);
		//获得该文件的输入流
		InputStream in = new FileInputStream(path);
		//获得输出流---通过response获得的输出流 用于向客户端写内容
		ServletOutputStream out = response.getOutputStream();
		//文件拷贝的模板代码
		int len = 0;
		byte[] buffer = new byte[1024];
		while((len=in.read(buffer))>0){
			out.write(buffer, 0, len);
		}

		in.close();
		//out.close();

	}

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

1）告知浏览器文件的类型：response.setContentType(文件的MIME类型);
2）告示浏览器文件的打开方式是下载：
response.setHeader(“Content-Disposition”,“attachment;filename=文件名称”);

但是，如果下载中文文件，页面在下载时会出现中文乱码或不能显示文件名的情况，原因是不同的浏览器默认对下载文件的编码方式不同，ie是UTF-8编码方式，而火狐浏览器是Base64编码方式。所里这里需要解决浏览器兼容性问题，解决浏览器兼容性问题的首要任务是要辨别访问者是ie还是火狐（其他），通过Http请求体中的一 个属性可以辨别

response响应码怎么获取 response获取响应内容_客户端_03

解决乱码方法如下（不要记忆–了解）：

if (agent.contains("MSIE")) {
		// IE浏览器
		filename = URLEncoder.encode(filename, "utf-8");
		filename = filename.replace("+", " ");
} else if (agent.contains("Firefox")) {
		// 火狐浏览器
BASE64Encoder base64Encoder = new BASE64Encoder();
		filename = "=?utf-8?B?"
				+ base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
} else {
		// 其它浏览器
		filename = URLEncoder.encode(filename, "utf-8");				
}

其中agent就是请求头User-Agent的值
具体代码如下：

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import sun.misc.BASE64Encoder;

public class DownLoadServlet2 extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		//*******文件名称是中文的下载*******


		//获得要下载的文件的名称
		String filename = request.getParameter("filename");//????.jpg
		//解决获得中文参数的乱码----
		filename = new String(filename.getBytes("ISO8859-1"),"UTF-8");//美女.jpg

		
		//获得请求头中的User-Agent
		String agent = request.getHeader("User-Agent");
		//根据不同浏览器进行不同的编码
		String filenameEncoder = "";
		if (agent.contains("MSIE")) {
			// IE浏览器
			filenameEncoder = URLEncoder.encode(filename, "utf-8");
			filenameEncoder = filenameEncoder.replace("+", " ");
		} else if (agent.contains("Firefox")) {
			// 火狐浏览器
			BASE64Encoder base64Encoder = new BASE64Encoder();
			filenameEncoder = "=?utf-8?B?"
					+ base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
		} else {
			// 其它浏览器
			filenameEncoder = URLEncoder.encode(filename, "utf-8");				
		}



		//要下载的这个文件的类型-----客户端通过文件的MIME类型去区分类型
		response.setContentType(this.getServletContext().getMimeType(filename));
		//告诉客户端该文件不是直接解析 而是以附件形式打开(下载)----filename="+filename 客户端默认对名字进行解码
		response.setHeader("Content-Disposition", "attachment;filename="+filenameEncoder);

		//获取文件的绝对路径
		String path = this.getServletContext().getRealPath("download/"+filename);
		//获得该文件的输入流
		InputStream in = new FileInputStream(path);
		//获得输出流---通过response获得的输出流 用于向客户端写内容
		ServletOutputStream out = response.getOutputStream();
		//文件拷贝的模板代码
		int len = 0;
		byte[] buffer = new byte[1024];
		while((len=in.read(buffer))>0){
			out.write(buffer, 0, len);
		}

		in.close();
		//out.close();

	}

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