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 ? data, such as for a cgi get 
          // request 
          stringtokenizer tokens = new stringtokenizer(line, " ?"); 
          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); 
  } 
}