* Location : 服务端用来告诉浏览器,请求需要重定向.(必须结合状态吗302使用)
Server : 服务端用来告诉浏览器,服务器的类型
* Content-Encoding: 服务端用来告诉浏览器,服务器对数据采用的编码（gzip、deflate）
Content-Length: 服务端用来告诉浏览器,响应正文的长度
Content-Language: 服务端用来告诉浏览器,zh-cn服务发送的文本的语言
*Content-Type: 服务端用来告诉浏览器,你要用哪个码表来解析二进制数据
* Last-Modified : 服务端用来告诉浏览器,访问资源的最后修改时间
*Refresh：服务端用来告诉浏览器,多长时间刷新一次
*Content-Disposition: 服务端用来告诉浏览器,以下载文件的方式打开文件
* Expires: -1 : 服务端用来告诉浏览器,不要缓存 Cache-Control:no-cache (1.1) Pragma: no-cache (1.0)
***** Set-Cookie: 服务端用来告诉浏览器,要存储的内容
doGet(HttpServletRequest request, HttpServletResponse response):处理页面上的get请求
HttpServletRequest request：代表了一个请求，从客户端浏览器发送过来的请求信息
当请求到达服务端的时候，tomcat会自动创建该对象，把所有的请求信息包装到了request对象中，就可以通过该对象拿到各种信息
HttpServletResponse response：代表了服务端向客户端的一个响应。
doPost(HttpServletRequest request, HttpServletResponse response)：处理页面上的post请求
ServletDeom1.java:
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; //演示响应头location public class ServletDemo1 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("ServletDemo1"); response.setStatus(302) ; //设置响应头 response.setHeader("Location", "/day07_00_httpresponse/servlet/ServletDemo2") ;//请求重定向 } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } } ServletDemo2.java:
package com.heiam.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; public class ServletDemo2 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("过来了啊"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } } 把项目部署到服务器上后，在浏览器中敲入：
http://localhost:8080/day07_00_httpresponse/servlet/ServletDemo1就访问到了项目了
在控制台中输出了对应的内容
服务端用来告诉浏览器,服务器对数据采用的编码（gzip、deflate）
ServletDemo3.java:
import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.PrintWriter; import java.util.zip.GZIPOutputStream; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; //演示响应头Content-Encoding编码格式 public class ServletDemo3 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String s = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" + "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" + "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" ; // s.length() //压缩的时候是一个字节(压缩流中需要的参数是字节数组)，先把字符串变成一个字节 byte[] bs = s.getBytes() ;//转换为字节数组的原因是往压缩流里写的数据要求是字节数组 System.out.println("压缩前的长度：" + bs.length); //创建一个字节数组输出流:因为可以从字节数组输出流中取出我们需要的数据 ByteArrayOutputStream baos = new ByteArrayOutputStream() ; //希望用Gzip压缩一下然后发送 //创建一个压缩流，包装了一下输出流 GZIPOutputStream gzip = new GZIPOutputStream(baos) ; //将数据进行压缩 gzip.write(bs) ; gzip.close() ; //从压缩流中拿出数据 bs = baos.toByteArray() ; //压缩后的数据 System.out.println("压缩后的长度： " + bs.length); //通知浏览器发送的数据格式是gzip response.setHeader("Content-Encoding", "gzip") ; response.getOutputStream().write(bs) ; } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
服务端用来告诉浏览器,你要用哪个码表来解析二进制数据
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; //演示Content_type响应头 public class ServletDemo4 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String s = "一个人的武林!!" ; //通知浏览器的Content-Type response.setHeader("Content-Type", "text/html;charset=UTF-8") ; response.getWriter().write(s) ; } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
服务端用来告诉浏览器,多长时间刷新一次
import java.io.IOException; import java.io.PrintWriter; import java.util.Random; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; //演示Refresh响应头 public class ServletDemo5 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //隔一段时间刷新自己 // response.setHeader("Refresh", "2") ; // response.getWriter().write("aa" + new Random().nextInt()) ; //隔2秒时间刷新到其他资源 response.setHeader("Refresh", "2;url=/day07_00_httpresponse/servlet/ServletDemo2") ; } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
服务端用来告诉浏览器,以下载文件的方式打开文件
import java.io.FileInputStream; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; //演示响应头Content-Disposition public class ServletDemo6 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //拿到图片的路径 String path = this.getServletContext().getRealPath("/WEB-INF/classes/1.gif") ; System.out.println(path); //创建一个输入流对象 FileInputStream is = new FileInputStream(path) ; byte[] bs = new byte[1024] ; int b = 0 ; //创建一个输出流对象 ServletOutputStream os = response.getOutputStream() ; //通知浏览器不要直接显示，而要下载下来再显示 response.setHeader("Content-Disposition", "attachment;filename=1.gif") ; //读取数据发送数据 while((b = is.read(bs)) != -1){ os.write(bs,0,b) ;//该流是由response对象产生的，不需要关闭，服务器会自动关闭 } is.close() ; os.close() ; } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } } * Expires: -1（立刻过期）
服务端用来告诉浏览器,不要缓存 Cache-Control:no-cache (1.1) Pragma: no-cache (1.0)
因为不清楚客户端使用的是什么版本的协议，所以都写上
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; //演示响应头Expires public class ServletDemo7 extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //通知浏览器不要缓存 response.setHeader("Expires", "-1") ; response.setHeader("Cache-control", "no-cache") ; response.setHeader("Pragma", "no-cache") ; response.getWriter().write("hello world!") ; } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
