tomcat作為web伺服器，想必大家做過web開發的都離不開tomcat了，值得慶幸的是tomcat也是開放原始碼的，最近準備好好琢磨琢磨tomcat的原始碼，還沒開始就已經感覺到不少的未知恐懼了，慢慢來把。 可能我的學習方式比較急功近利，但是這種方式收效也快，自己記得在<<Java程式設計師 上班那點事兒>>裡作者寫過一個最簡單的web伺服器實現，自己在網上也比較了一下其它的版本，還是感覺那本書裡的版本比較好，在此分享出來，因為時間緊，照著書敲了一遍程式碼，竟然發現裡面有一些很細小的錯誤，自己準備在這個基礎上好好改進一把。 首先來看看web伺服器的一些基本原理，我們的實驗是基於socket的，開放了一個指定的埠，然後會啟用對應的執行緒來處理瀏覽器中的請求。如果檔案不存在，會報出404錯誤，否則會解析檔案的內容。 HttpServer類是後臺服務類，會開放對應的埠和socket來處理瀏覽發出的請求。 HttpThread類是接受瀏覽器傳送請求的類，通過Receive和Answer來接受和處理瀏覽器傳送的請求，然後返回到客戶端中。

package new_test;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;
public class HttpServer { 
public static String ROOT="./wwwroot";
public static String defaultPage="index.html";

    public static void main(String[] args) throws IOException{ 
 
            ServerSocket ss = new ServerSocket(8080); 
            while(true){
            Socket s=ss.accept();
                System.out.println("Accept Connection...:");                                   
                 new HttpThread(s).start();
            }        
    } 
}


package new_test;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import
} java.net.Socket;


public class HttpThread extends Thread {


private Socket socket;


public HttpThread(Socket s) {
this.socket = s;


public void run() {
InputStream ins = null;
OutputStream ous = null;
try {
ous = socket.getOutputStream();
ins = socket.getInputStream();
Receive rcv = new Receive(ins);
String sURL = rcv.parse();
System.out.println("sURL is " + sURL);


if (sURL.equals("/")) {
sURL = HttpServer.defaultPage;
}
Answer ans = new Answer(ous);
ans.send(sURL);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (ins != null) {
ins.close();
}
if (ous != null) {
ous.close();
}
if (socket != null) {
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

package new_test;
import java.io.IOException;
import java.io.InputStream;


public class Receive {
InputStream in = null;


public Receive(InputStream ins) {
this.in = ins;
}


public String parse() {
StringBuffer receiveStr = new StringBuffer(2048);
int i ;
byte[] buffer = new byte[2048];
try {
i = in.read(buffer);
} catch (IOException e) {
i = -1;
}
for (int j = 0; j < i; j++) {
receiveStr.append((char)buffer[j]);


}
return getUri(receiveStr.toString());
}


private String getUri(String receiveStr) {
int index1, index2;
System.out.println("receiveStr is " + receiveStr);
index1 = receiveStr.indexOf(" ");
if (index1 != -1) {
index2 = receiveStr.indexOf(" ", index1 + 1);
if (index2 > index1) {
return receiveStr.substring(index1 + 1, index2);
}
}
return null;
}


}


package new_test;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;

public class Answer {
OutputStream out = null;

public Answer(OutputStream ous) {
this.out = ous;
}


public void send(String pageFile) {
byte[] bytes = new byte[2048];


FileInputStream fis = null;
try {
File file = new File(HttpServer.ROOT, pageFile);
if (file.exists()) {


fis = new FileInputStream(file);
int ch = fis.read(bytes, 0, 2048);
String sBody = new String(bytes, 0);
String sendMessage = "HTTP/1.1 200 OKrn"
+ "Content-Type:text/htmlrn" + "Content-Length:" + ch
+ "rn" + "rn" + sBody;
out.write(sendMessage.getBytes());
} else {
String errorMessage = "Http/1.1 404 File NOT FOUNDrn"
+ "Content-Type:text/htmlrn"
+ "Content-Length:23rn" + "rn"
+ "<h1>File Not Found</h1>";
out.write(errorMessage.getBytes());
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fis != null) {
try {
fis.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}


}


}

 

一個簡單呼叫的情況就是，如果不存在對應的頁面會直接丟擲File Not Found的錯誤資訊