Java 实现 web服务器的简单实例

import java.util.*; 
 
// Chapter 8, Listing 3 
public class WebServerDemo { 
  // Directory of HTML pages and other files 
  protected String docroot; 
  // Port number of web server 
  protected int port; 
  // Socket for the web server 
  protected ServerSocket ss; 
 
  // Handler for a HTTP request 
  class Handler extends Thread { 
    protected Socket socket; 
    protected PrintWriter pw; 
    protected BufferedOutputStream bos; 
    protected BufferedReader br; 
    protected File docroot; 
 
    public Handler(Socket _socket, String _docroot) throws Exception { 
      socket = _socket; 
      // Get the absolute directory of the filepath 
      docroot = new File(_docroot).getCanonicalFile(); 
    } 
 
    public void run() { 
      try { 
        // Prepare our readers and writers 
        br = new BufferedReader(new InputStreamReader( 
            socket.getInputStream())); 
        bos = new BufferedOutputStream(socket.getOutputStream()); 
        pw = new PrintWriter(new OutputStreamWriter(bos)); 
 
        // Read HTTP request from user (hopefully GET /file...... ) 
        String line = br.readLine(); 
 
        // Shutdown any further input 
        socket.shutdownInput(); 
 
        if (line == null) { 
          socket.close(); 
          return; 
        } 
        if (line.toUpperCase().startsWith("GET")) { 
          // Eliminate any trailing " "); 
          tokens.nextToken(); 
          String req = tokens.nextToken(); 
 
          // If a path character / or / is not present, add it to the 
          // document root 
          // and then add the file request, to form a full filename 
          String name; 
          if (req.startsWith("/") || req.startsWith("//")) 
            name = this.docroot + req; 
          else 
            name = this.docroot + File.separator + req; 
 
          // Get absolute file path 
          File file = new File(name).getCanonicalFile(); 
 
          // Check to see if request doesn't start with our document 
          // root .... 
          if (!file.getAbsolutePath().startsWith( 
              this.docroot.getAbsolutePath())) { 
            pw.println("HTTP/1.0 403 Forbidden"); 
            pw.println(); 
          } 
          // ... if it's missing ..... 
          else if (!file.exists()) { 
            pw.println("HTTP/1.0 404 File Not Found"); 
            pw.println(); 
          } 
          // ... if it can't be read for security reasons .... 
          else if (!file.canRead()) { 
            pw.println("HTTP/1.0 403 Forbidden"); 
            pw.println(); 
          } 
          // ... if its actually a directory, and not a file .... 
          else if (file.isDirectory()) { 
            sendDir(bos, pw, file, req); 
          } 
          // ... or if it's really a file 
          else { 
            sendFile(bos, pw, file.getAbsolutePath()); 
          } 
        } 
        // If not a GET request, the server will not support it 
        else { 
          pw.println("HTTP/1.0 501 Not Implemented"); 
          pw.println(); 
        } 
 
        pw.flush(); 
        bos.flush(); 
      } catch (Exception e) { 
        e.printStackTrace(); 
      } 
      try { 
        socket.close(); 
      } catch (Exception e) { 
        e.printStackTrace(); 
      } 
    } 
 
    protected void sendFile(BufferedOutputStream bos, PrintWriter pw, 
        String filename) throws Exception { 
      try { 
        java.io.BufferedInputStream bis = new java.io.BufferedInputStream( 
            new FileInputStream(filename)); 
        byte[] data = new byte[10 * 1024]; 
        int read = bis.read(data); 
 
        pw.println("HTTP/1.0 200 Okay"); 
        pw.println(); 
        pw.flush(); 
        bos.flush(); 
 
        while (read != -1) { 
          bos.write(data, 0, read); 
          read = bis.read(data); 
        } 
        bos.flush(); 
      } catch (Exception e) { 
        pw.flush(); 
        bos.flush(); 
      } 
    } 
 
    protected void sendDir(BufferedOutputStream bos, PrintWriter pw, 
        File dir, String req) throws Exception { 
      try { 
        pw.println("HTTP/1.0 200 Okay"); 
        pw.println(); 
        pw.flush(); 
 
        pw.print("<html><head><title>Directory of "); 
        pw.print(req); 
        pw.print("</title></head><body><h1>Directory of "); 
        pw.print(req); 
        pw.println("</h1><table border=/"0/">"); 
 
        File[] contents = dir.listFiles(); 
 
        for (int i = 0; i < contents.length; i++) { 
          pw.print("<tr>"); 
          pw.print("<td><a href="/" rel="external nofollow" rel="external nofollow" mce_href="/" rel="external nofollow" rel="external nofollow" ""); 
          pw.print(req); 
          pw.print(contents[i].getName()); 
          if (contents[i].isDirectory()) 
            pw.print("/"); 
          pw.print("/">"); 
          if (contents[i].isDirectory()) 
            pw.print("Dir -> "); 
          pw.print(contents[i].getName()); 
          pw.print("</a></td>"); 
          pw.println("</tr>"); 
        } 
        pw.println("</table></body></html>"); 
        pw.flush(); 
      } catch (Exception e) { 
        pw.flush(); 
        bos.flush(); 
      } 
    } 
  } 
 
  // Check that a filepath has been specified and a port number 
  protected void parseParams(String[] args) throws Exception { 
    switch (args.length) { 
    case 1: 
    case 0: 
      System.err.println("Syntax: <jvm> " + this.getClass().getName() 
          + " docroot port"); 
      System.exit(0); 
 
    default: 
      this.docroot = args[0]; 
      this.port = Integer.parseInt(args[1]); 
      break; 
    } 
  } 
 
  public WebServerDemo(String[] args) throws Exception { 
    System.out.println("Checking for paramters"); 
 
    // Check for command line parameters 
    parseParams(args); 
 
    System.out.print("Starting web server...... "); 
 
    // Create a new server socket 
    this.ss = new ServerSocket(this.port); 
 
    System.out.println("OK"); 
 
    for (;;) { 
      // Accept a new socket connection from our server socket 
      Socket accept = ss.accept(); 
 
      // Start a new handler instance to process the request 
      new Handler(accept, docroot).start(); 
    } 
  } 
 
  // Start an instance of the web server running 
  public static void main(String[] args) throws Exception { 
    WebServerDemo webServerDemo = new WebServerDemo(args); 
  } 
}