1 第一章、 一個簡單的web服務器
這一章主要介紹一個web服務器是怎樣工作的，一個web服務器通常也叫Http服務器因爲通過http協議與客戶端（瀏覽器）交互。
1.1 超文本傳輸協議HTTP
HTTP協議包括HTTP Request和HTTP Response
Client初始化連接的時候爲傳送一個HTTP Request，包括三個部分：
方法-URI-協議/版本
Request 頭
Request 體
與Request HTTP相似，HTTP Response也包括三個部分：
協議-狀態-描述
Response 頭
Response 體
1.2 Socket 和 ServerSocket
套接字socket代表客戶端與服務器連接，你可以通過他與服務器建立連接，可以指定host和port，Java中用Socket類來建立，有多個構造函數。
可以通過ServerSocket建立http服務器或者ftp服務器。
1.3 應用
在eclipse中建立java工程tomcat_study，具體結構如下：
src：存放java原文件
webroot: 存放html文件
lib：所需庫
webapps:應用程序
這裏實現一個服務器應用，主要實現三個類：
HttpServer
Request
Response
在main方法中創建HttpServer實例，並調用它的await方法，該方法監聽制定端口的Http請求，處理以後返回給客戶端，直到收到shutdown命令。
package com.ex01.pyfrmont;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
/**
*
* 服務器實現類，await方法，該方法監聽制定端口的Http請求，
* 處理以後返回給客戶端，直到收到shutdown命令
* @author peng_yf
* @version 1.0,2011-08-20
* @since 1.0
*
*/
public class HttpServer {
/**
* WEB_ROOT is the directory where our HTML and other files reside.
* For this packge,WEB_ROOT is the "webroot" directory under the
* working directory.
* The working directory is the location in the file system from
* where the java command was invoked.
*/
public static final String WEB_ROOT =
System.getProperty("user.dir") + File.separator + "webroot";
/**
* shutdown command
*/
private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";
/**
* the shutdown command received
*/
private boolean shutdown = false;
/**
* @param args
*/
public static void main(String[] args) {
HttpServer server = new HttpServer();
server.await();
}
private void await() {
ServerSocket serverSocket = null;
int port = 8080;
try{
serverSocket = new ServerSocket(port,1,InetAddress.getByName("127.0.0.1"));
}catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
//Loop waiting for a request
while(!shutdown){
Socket socket = null;
InputStream input = null;
OutputStream output = null;
try{
socket = serverSocket.accept();
input = socket.getInputStream();
output = socket.getOutputStream();
//create Request object and parse
Request request = new Request(input);
request.parse();
//create Response object
Response response = new Response(output);
response.setRequest(request);
response.sendStaticResource();
//close the socket
socket.close();
//check if the previous URI is a shutdown command
shutdown = request.getUri().equals(SHUTDOWN_COMMAND);
}catch (Exception e) {
e.printStackTrace();
continue;
}
}
}
}
Request代表一個HTTP請求，用Socket中與客戶端通信的輸入流來構造，可以通過其中的read方法讀取HTTP格式數據。
package com.ex01.pyfrmont;
import java.io.IOException;
import java.io.InputStream;
/**
* 代表一個HTTP請求，用Socket中與客戶端通信的輸入流來構造，可
* 以通過其中的read方法讀取HTTP格式數據
* @author Peng_yf
* @version 1.0,2011-08-20
* @since 1.0
*/
public class Request {
private InputStream input;
private String uri;
public Request(InputStream input) {
this.input = input;
}
public void parse() {
// Read a set of characters from the socket
StringBuffer request = new StringBuffer(2048);
int i;
byte[] buffer = new byte[2048];
try {
i = input.read(buffer);
} catch (IOException e) {
e.printStackTrace();
i = -1;
}
for(int j=0; j < i; j++){
request.append((char)buffer[j]);
}
System.out.println(request.toString());
uri = parseUri(request.toString());
}
private String parseUri(String requestString){
int index1,index2;
index1 = requestString.indexOf(' ');
while(index1 != -1){
index2 = requestString.indexOf(' ', index1+1);
if(index1 < index2){
return requestString.substring(index1+1,index2);
}
}
return null;
}
public String getUri(){
return this.uri;
}
}
Response代表HTTP響應。
package com.ex01.pyfrmont;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;
/**
* HTTP Response = Status-Line
* *((general-header|response-header|entity-header)CRLF)
* CRLF
* [message body]
* Status-Line=HTTP-Version SP Status-Code SP Response-Phrase CRLF
* @author Peng_yf
* @version 1.0, 2011-08-20
* @since 1.0
*
*/
public class Response {
private static final int BUFFER_SIZE = 1024;
OutputStream output;
Request request;
public Response(OutputStream output) {
this.output = output;
}
public void setRequest(Request request) {
this.request = request;
}
public void sendStaticResource() {
byte[] bytes = new byte[BUFFER_SIZE];
FileInputStream fis = null;
try {
File file = new File(HttpServer.WEB_ROOT,request.getUri());
if(file.exists()){
fis = new FileInputStream(file);
int ch = fis.read(bytes,0,BUFFER_SIZE);
if(ch != -1){
output.write(bytes, 0, ch);
ch = fis.read(bytes,0,BUFFER_SIZE);
}
}else{
//file not found
String errorMessage = "HTTP/1.1 404 File Not Found￥r￥n" +
"Content-Type:text/html￥r￥n" +
"Content-Length:23￥r￥n"+
"￥r￥n" +
"<h1> File Not Found</h1>";
output.write(errorMessage.getBytes());
}
} catch (Exception e) {
//thrown if cannot instantiate a File object.
System.out.println(e.getMessage());
e.printStackTrace();
}finally{
if(fis != null){
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
測試運行時，運行HttpServer，在界面輸入：
http://localhost:8080/index.html
將會在瀏覽器中顯示index.html中的內容。