how tomcat works 讀書筆記(一)----------一個簡單的web伺服器

標籤：http協議   原始碼   tomcat   .重構   

http協議若是兩個人能正常的說話交流,那麼他們間必定有一套統一的語言規則<在網路上伺服器與用戶端能交流也依賴與一套規則,它就是我們說的http規則(超文字傳輸通訊協定 (HTTP)Hypertext transfer protocol)。
http分兩部分,一個是請求(用戶端發給伺服器),一個是回複(伺服器發給用戶端)。
先看http請求 

下面就是一個http請求的例子,其中的各項參數,請查閱相關資料。(http://www.cnblogs.com/yin-jingyu/archive/2011/08/01/2123548.html)

http回複

下面就是http回複的例子,除了這個圖之外,後面的部分就是大家看到的頁面的原始碼

socket我們一般說的socket,廣義上包含java.net包下的Socket類與ServerSocekt類。
另一方面有基於tcp的網路編程也有基於udp的網路編程,其中差別大家百度,這裡只談tcp。
定義性的東西大家可以查看各種資料(個人推薦尚學堂 馬士兵老師講解的socket部分視頻,但在看socket之前建議大家先看io部分),帶大家看一段代碼,大家應該就會知道socket編程的大致原理了。(代碼來自馬士兵老師的講義)

import java.net.*;import java.io.*;public class TCPServer {public static void main(String[] args) throws Exception {ServerSocket ss = new ServerSocket(6666);      //在原生TCP6666號連接埠上監聽while(true) {Socket s = ss.accept();                //ServerSocket的accept為阻塞式方法,只有當它監聽到一個請求時                                       //它才會執行                        System.out.println("a client connect!");DataInputStream dis = new DataInputStream(s.getInputStream());//獲得用戶端向自己說的"話"                                       //InputStream 從外部指向記憶體System.out.println(dis.readUTF());     //按照uft-8的格式讀取內容dis.close();s.close();}}}import java.net.*;import java.io.*;public class TCPClient {public static void main(String[] args) throws Exception {Socket s = new Socket("127.0.0.1", 6666);       //串連127.0.0.1(本機)的tcp連接埠6666OutputStream os = s.getOutputStream();          //獲得一條線路,來給伺服器"說話"DataOutputStream dos = new DataOutputStream(os);//對這個線路進行封裝Thread.sleep(3000);                             //"暫停"3秒dos.writeUTF("hello server!");                  //對伺服器說 hello server! dos.flush();dos.close();s.close();}}

先運行server端,再運行client端。當運行client端後,控制台首先會列印a client connect!三秒之後會列印hello server! 
類比一個最最最基礎的tomcat

import java.net.Socket;import java.net.ServerSocket;import java.net.InetAddress;import java.io.InputStream;import java.io.OutputStream;import java.io.IOException;import java.io.File;public class HttpServer {  /** WEB_ROOT is the directory where our HTML and other files reside.   *  For this package, 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;  public static void main(String[] args) {    HttpServer server = new HttpServer();    server.await();  }  public void await() {    ServerSocket serverSocket = null;    int port = 8080;    try {      serverSocket =  new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));                  //這個1是什麼功能 參加 http://www.51cto.com/art/200702/40196_1.htm    }    catch (IOException e) {      e.printStackTrace();      System.exit(1);    }    // Loop waiting for a request    while (!shutdown) {  //最開始的時候 shutdown為false 這段話會執行      Socket socket = null;      InputStream input = null;      OutputStream output = null;      try {        socket = serverSocket.accept();   //只有當有用戶端請求時 它才會運行 阻塞式方法!        input = socket.getInputStream();  //裡面放的是用戶端對伺服器說的話        output = socket.getOutputStream();//這裡面將要放的是伺服器要對用戶端說的話        // create Request object and parse        Request request = new Request(input);        request.parse();                  //參見request        // 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;      }    }  }}

import java.io.InputStream;import java.io.IOException;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]);   //將用戶端的請求加到request(StringBuffer)中    }    System.out.print(request.toString());    uri = parseUri(request.toString());     System.out.print(uri****);  }  /**  *看看System.out.print(uri****); 就不用解釋這個方法了  *  *  **/  private String parseUri(String requestString) {    int index1, index2;    index1 = requestString.indexOf(' ');    if (index1 != -1) {      index2 = requestString.indexOf(' ', index1 + 1);      if (index2 。 index1)        return requestString.substring(index1 + 1, index2);    }    return null;  }  public String getUri() {    return uri;  }}

import java.io.OutputStream;import java.io.IOException;import java.io.FileInputStream;import java.io.File;/*  HTTP Response = Status-Line    *(( general-header | response-header | entity-header ) CRLF)    CRLF    [ message-body ]    Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF*/public class Response {  private static final int BUFFER_SIZE = 1024;  Request request;  OutputStream output;  public Response(OutputStream output) {    this.output = output;  }  public void setRequest(Request request) {    this.request = request;  }  public void sendStaticResource() throws IOException {    byte[] bytes = new byte[BUFFER_SIZE];    FileInputStream fis = null;    try {      System.out.println(HttpServer.WEB_ROOT+"  ss  "+request.getUri());      File file = new File(HttpServer.WEB_ROOT, request.getUri());   //串連使用者請求的"檔案"      if (file.exists()) {        fis = new FileInputStream(file);        int ch = fis.read(bytes, 0, BUFFER_SIZE);       //把檔案裡的東西讀出來放到bytes字元數組裡        while (ch!=-1) {                                //把bytes數組裡的東西放到要給用戶端回複的流裡面          output.write(bytes, 0, ch);          ch = fis.read(bytes, 0, BUFFER_SIZE);        }      }      else {                                            //要是檔案不存在  不解釋        // 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.toString() );    }    finally {      if (fis!=null)        fis.close();    }  }}

首先如果大家用的是Eclipse,那麼沒有任何問題,如果大家是用命令列的形式的話會存在一個問題,HttpServer與Response兩個類相互依賴,先編譯誰?
解決辦法 cd到三個類的目錄 然後 javac *.java


等啟動HttpServer後
在瀏覽器輸入localhost:8080/index.html

顯示如下 

明白了吧 我們把index.html放到D:\尚學堂 j2ee\javase\尚學堂科技_馬士兵_J2SE_5.0_第01章_JAVA簡介_原始碼_及重要說明\java\Socket\no\WebContent 目錄下

index.html內容如下
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
我是index
</body>
</html>

再次請求 如下

大家一定很奇怪,我為什麼不用Firefox或這個Chrome,找個EditPlus點過來點過去。
大家試試就知道了,Firefox不知道因為什麼原因,在地址欄敲斷行符號後,會發出兩次請求。結果就是報錯。

再試試http://localhost:8080/SHUTDOWN

程式退出

how tomcat works 讀書筆記(一)----------一個簡單的web伺服器