securitypolicy.java

一个用java语言编写的网络爬虫程序

/*
 * WebSPHINX web crawling toolkit
 * Copyright (C) 1998,1999 Carnegie Mellon University 
 * 
 * This library is free software; you can redistribute it
 * and/or modify it under the terms of the GNU Library
 * General Public License as published by the Free Software 
 * Foundation, version 2.
 *
 * WebSPHINX homepage: http://www.cs.cmu.edu/~rcm/websphinx/
 */
package websphinx;

import java.net.*;
import java.io.*;
import java.util.Vector;

public class SecurityPolicy {
    private File tempDir;
    private Vector temps = new Vector ();

    public SecurityPolicy () {
        String tempDirName;
        
        try {
            tempDirName = System.getProperty ("websphinx.temp.directory");
        } catch (SecurityException e) {
            tempDirName = null;
        }

        if (tempDirName == null) {
            String os = System.getProperty("os.name");
            tempDirName = (os.startsWith ("Windows"))
                            ? "c:\\temp\\"
                            : "/tmp/";
        }
        
        if (!(tempDirName.endsWith ("/") ||
              tempDirName.endsWith (File.separator)))
            tempDirName += "/";
        
        tempDir = new File (tempDirName);
    }

    public URLConnection openConnection (URL url) throws IOException {
        URLConnection conn = url.openConnection ();
        conn.connect ();
        return conn;
    }

    public URLConnection openConnection (Link link) throws IOException {
        // get the URL
        int method = link.getMethod();
        URL url;
        switch (method) {
            case Link.GET:
                url = link.getPageURL();
                break;
            case Link.POST:
                url = link.getServiceURL();
                break;
            default:
                throw new IOException ("Unknown HTTP method " + link.getMethod());
        }

        // open a connection to the URL
        URLConnection conn = url.openConnection ();

        // set up request headers
        DownloadParameters dp = link.getDownloadParameters ();
        if (dp != null) {
            conn.setAllowUserInteraction (dp.getInteractive ());
            conn.setUseCaches (dp.getUseCaches ());

            String userAgent = dp.getUserAgent ();
            if (userAgent != null)
                conn.setRequestProperty ("User-Agent", userAgent);

            String types = dp.getAcceptedMIMETypes ();
            if (types != null)
                conn.setRequestProperty ("accept", types);
        }

        // submit the query if it's a POST (GET queries are encoded in the URL)
        if (method == Link.POST) {
//#ifdef JDK1.1 
            if (conn instanceof HttpURLConnection)
                ((HttpURLConnection)conn).setRequestMethod ("POST");
//#endif JDK1.1
            
            String query = link.getQuery ();
            if (query.startsWith ("?"))
                query = query.substring (1);

            conn.setDoOutput (true);
            conn.setRequestProperty ("Content-type",
                                     "application/x-www-form-urlencoded");
            conn.setRequestProperty ("Content-length", String.valueOf(query.length()));

            // commence request
//#ifdef JDK1.1 
            PrintStream out = new PrintStream (conn.getOutputStream ());
//#endif JDK1.1
/*#ifdef JDK1.0
            PrintStream out = new PrintStream (conn.getOutputStream ());
#endif JDK1.0*/
            out.print (query);
            out.flush ();
        }

        conn.connect ();
        return conn;
    }

  public InputStream readFile (File file) throws IOException {
    return new FileInputStream (file);
  }

  public OutputStream writeFile (File file, boolean append) throws IOException {
    //#ifdef JDK1.1
    return new FileOutputStream (file.toString(), append);
    //#endif JDK1.1
    /*#ifdef JDK1.0
    if (append)
        throw new IOException ("Can't append to files under JDK 1.0");
    else
        return new FileOutputStream (file.toString());
    #endif JDK1.0*/        
  }

    public RandomAccessFile readWriteFile (File file) throws IOException {
        return new RandomAccessFile (file, "rw");
    }
    
    public void makeDir (File file) throws IOException {
        file.mkdirs ();
    }

    public File getTemporaryDirectory () {
        return tempDir;
    }

    public File makeTemporaryFile (String basename, String extension) {
        File dir = getTemporaryDirectory ();
        File f;
        synchronized (temps) {
            do
                f = new File (dir,
                              basename
                              + String.valueOf ((int)(Math.random() * 999999))
                              + extension);
            while (temps.contains (f) || f.exists());

            temps.addElement (f);
        }
        return f;
    }

    public void deleteAllTempFiles () {
        synchronized (temps) {
            for (int i=0; i<temps.size(); ++i) {
                File f = (File)temps.elementAt(i);
                f.delete ();
            }
            temps.setSize (0);
        }
    }

  /*
   * Global security policy
   *
   */

  private static SecurityPolicy thePolicy = findPolicy ();

  private static SecurityPolicy findPolicy () {
    try {
      String policyName = System.getProperty ("websphinx.policy");

      if (policyName == null)
        return new SecurityPolicy ();
      else {
        try {
          Class cls = Class.forName (policyName);
          return (SecurityPolicy)cls.newInstance ();
        } catch (Throwable t) {
          System.err.println ("websphinx.SecurityPolicy: cannot instantiate " + policyName);
          System.exit (-1);
          return null; // doesn't get here
        }
      }
    }
    catch (Throwable t) {
      // assume we're running in a sandbox (like a Web browser)
      String browserName;
      try {
          browserName = System.getProperty ("browser");
      } catch (Throwable e) {
          browserName = null;
      }
      if (browserName == null)
          browserName = "";

      String browserVersion;
      try {
          browserVersion = System.getProperty ("browser.version");
      } catch (Throwable e) {
          browserVersion = null;
      }
      if (browserVersion == null)
          browserVersion = "";

      if (browserName.startsWith ("Netscape")
           && browserVersion.startsWith ("4."))
        return new Netscape4Policy ();
      else
        return new SecurityPolicy (); // FIX: replace with BrowserPolicy that pops up dialog boxes
    }
  }

    public static SecurityPolicy getPolicy () {
        return thePolicy;
    }

}