Java 实现 web服务器的简单实例

Java 实现 web服务器的简单实例

实例代码：

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);
  }
} 

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