自己动手，写个Web服务器(Java版)——第一篇、浏览器和Web服务器的语言Http

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浏览器如何根Web服务器交谈呢？请看下图

浏览器和Web服务器通过一个叫TCP的管子通话。浏览器先说：我要……。Web服务器回答：给你……。如此往复。Web服务器不会主动回答的，只有浏览器发出请求，Web服务器才会回答。

浏览器和Web服务器都是机器，不懂人的语言。它们有自己的语言——http。其中请求和响应的语法都差不多。都是由头、（空行）、体组合而成。头是由一行一行的格式如：name： value（回车换行）的行组成的。

下面就来写两个简单的程序看看浏览器和Web服务器到底说了些什么吧：）

1 浏览器的请求

Server是用Java写第一版的Web服务器。它打开一个80端口的ServerSocket等待浏览器连入。当浏览器接入后，把浏览器发送的请求打印出来。

package mywebserver1;

import java.io.BufferedReader;

import java.io.IOException;

import java.io.InputStreamReader;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.StringTokenizer;

/**

* @author allen

* @version 0.1

public class Server {

public static void main(String[] args) {

try {

ServerSocket ss = new ServerSocket(80);

Socket s = ss.accept();

BufferedReader br = new BufferedReader(new InputStreamReader(s

.getInputStream()));

String requestLine = "";

char[] body;

boolean haveBody = false;

int length = 0;

do {

requestLine = br.readLine();

System.out.println(requestLine);

// post方式提交的请求还要取得，请求体的内容

if (requestLine.startsWith("Content-Length")) {

StringTokenizer st = new StringTokenizer(requestLine, ":");

st.nextToken();

String bodyLength = st.nextToken().trim();

length = Integer.parseInt(bodyLength);

haveBody = true;

}

if (requestLine.equals("") && haveBody) {

body = new char[length];

br.read(body, 0, length);

System.out.println(new String(body));

}

} while (!requestLine.equals(""));

br.close();

s.close();

ss.close();

} catch (IOException e) {

e.printStackTrace();

} finally {

//资源清理代码

}

以下是控制台打印出的浏览器请求的内容

1. Get方式

GET / HTTP/1.1

Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-silverlight, */*

Accept-Language: zh-cn

Accept-Encoding: gzip, deflate

If-Modified-Since: Tue, 02 Sep 2008 06:15:50 GMT

If-None-Match: W/"648-1220336150812"

User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; aff-kingsoft-ciba)

Host: 127.0.0.1

Connection: Keep-Alive

Cookie: __utma=96992031.200084460.1247665275.1247665275.1247665275.1; __utmz=96992031.1247665275.1.1.utmccn=(direct)|utmcsr=(direct)|utmcmd=(none)

2. Post方式

POST / HTTP/1.1

Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-silverlight, */*

Accept-Language: zh-cn

Content-Type: application/x-www-form-urlencoded

Accept-Encoding: gzip, deflate

User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; aff-kingsoft-ciba)

Host: 127.0.0.1

Content-Length: 19

Connection: Keep-Alive

Cache-Control: no-cache

Cookie: __utma=96992031.200084460.1247665275.1247665275.1247665275.1; __utmz=96992031.1247665275.1.1.utmccn=(direct)|utmcsr=(direct)|utmcmd=(none)

user=Mike&pass=1234

这个是测试用的index.html页面

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

<HTML>

<HEAD>

</HEAD>

<BODY>

<a href="http://127.0.0.1/">Get方式提交的请求！</a>

</form>

</BODY>

</HTML>

2 Web服务器的回应

Client.java是测试用的客户端。它手工构造了一个请求（访问的是www.baidu.com），然后把服务器的响应打出来。

/**

package mywebserver1;

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.IOException;

import java.io.InputStreamReader;

import java.io.OutputStreamWriter;

import java.net.InetAddress;

import java.net.Socket;

import java.net.UnknownHostException;

import java.nio.charset.Charset;

import java.util.StringTokenizer;

/**

* @author allen

* @version 0.1

public class Client {

/**

* @param args

public static void main(String[] args) {

String host = "www.baidu.com";

String resource = "/";

int port = 80;

//手工构造请求

StringBuilder request = new StringBuilder();

request.append("GET " + resource + " HTTP/1.1/n");

request.append("/n");

System.out.println("请求是：/n" + request.toString());

try {

InetAddress[] ipaddr = InetAddress.getAllByName(host);

Socket s = new Socket(ipaddr[0], port);

BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s

.getOutputStream()));

bw.write(request.toString());

bw.flush();

// 发送完请求，开始接收响应

BufferedReader br = new BufferedReader(new InputStreamReader(s

.getInputStream()));

String requestLine = "";

char[] body;

boolean haveBody = false;

int length = 0;

boolean ifchunked = false;

do {

requestLine = br.readLine();

System.out.println(requestLine);

// 响应体的取得，与请求体的取得类似。

if (requestLine.startsWith("Content-Length")) {

StringTokenizer st = new StringTokenizer(requestLine, ":");

st.nextToken();

String bodyLength = st.nextToken().trim();

length = Integer.parseInt(bodyLength);

haveBody = true;

}

if (requestLine.startsWith("Transfer-Encoding")) {

StringTokenizer st = new StringTokenizer(requestLine, ":");

st.nextToken();

String transferEncoding = st.nextToken().trim();

if ("chunked".equalsIgnoreCase(transferEncoding)) {

ifchunked = true;

}

//读取响应Body

if (requestLine.equals("") && haveBody) {

body = new char[length];

br.read(body, 0, length);

String responseBody = new String(body);

System.out.println(responseBody.length());

System.out.println(responseBody);

}

//响应的Transfer-Encoding是chunked，需要特殊的处理

if (requestLine.equals("") && ifchunked) {

char[] chunkedbody = new char[1024];

int readin = 0;

do {

readin = br.read(chunkedbody);

System.out.println(new String(chunkedbody, 0, readin));

} while (readin > 0);

}

} while (!requestLine.equals(""));

bw.close();

br.close();

s.close();

} catch (UnknownHostException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

以下是百度返回的响应

HTTP/1.1 200 OK

Date: Sun, 26 Jul 2009 13:34:30 GMT

Server: BWS/1.0

Content-Length: 3509

Content-Type: text/html

Cache-Control: private

Expires: Sun, 26 Jul 2009 13:34:30 GMT

Set-Cookie: BAIDUID=1FAAFC4F63BD53DED54944E06B8FACEA:FG=1; expires=Sun, 26-Jul-39 13:34:30 GMT; path=/; domain=.baidu.com

P3P: CP=" OTI DSP COR IVA OUR IND COM "

3509

<html><head><meta http-equiv=Content-Type content="text/html;charset=gb2312"><title>百度一下，你就知道</title>省略了</html>_