url.java

gcc的组建

  public int hashCode()
  {
    if (hashCode != 0)
      return hashCode; // Use cached value if available.
    else
      return ph.hashCode(this);
  }

  /**
   * Returns a URLConnection object that represents a connection to the remote
   * object referred to by the URL. The URLConnection is created by calling the
   * openConnection() method of the protocol handler
   *
   * @return A URLConnection for this URL
   *
   * @exception IOException If an error occurs
   */
  public URLConnection openConnection() throws IOException
  {
    return ph.openConnection(this);
  }

  /**
   * Opens a connection to this URL and returns an InputStream for reading
   * from that connection
   *
   * @return An <code>InputStream</code> for this URL.
   *
   * @exception IOException If an error occurs
   */
  public InputStream openStream() throws IOException
  {
    return openConnection().getInputStream();
  }

  /**
   * Tests whether or not another URL refers to the same "file" as this one.
   * This will be true if and only if the passed object is not null, is a
   * URL, and matches all fields but the ref (ie, protocol, host, port,
   * and file);
   *
   * @param url The URL object to test with
   *
   * @return true if URL matches this URL's file, false otherwise
   */
  public boolean sameFile(URL url)
  {
    return ph.sameFile(this, url);
  }

  /**
   * Sets the specified fields of the URL. This is not a public method so
   * that only URLStreamHandlers can modify URL fields. This might be called
   * by the <code>parseURL()</code> method in that class. URLs are otherwise
   * constant. If the given protocol does not exist, it will keep the previously
   * set protocol.
   *
   * @param protocol The protocol name for this URL
   * @param host The hostname or IP address for this URL
   * @param port The port number of this URL
   * @param file The "file" portion of this URL.
   * @param ref The anchor portion of this URL.
   */
  protected void set(String protocol, String host, int port, String file,
                     String ref)
  {
    URLStreamHandler protocolHandler = null;
    protocol = protocol.toLowerCase();
    if (! this.protocol.equals(protocol))
      protocolHandler = getURLStreamHandler(protocol);
    
    // It is an hidden feature of the JDK. If the protocol does not exist,
    // we keep the previously initialized protocol.
    if (protocolHandler != null)
      {
	this.ph = protocolHandler;
	this.protocol = protocol;
      }
    this.authority = "";
    this.port = port;
    this.host = host;
    this.file = file;
    this.ref = ref;

    if (host != null)
      this.authority += host;
    if (port >= 0)
      this.authority += ":" + port;

    hashCode = hashCode(); // Used for serialization.
  }

  /**
   * Sets the specified fields of the URL. This is not a public method so
   * that only URLStreamHandlers can modify URL fields. URLs are otherwise
   * constant. If the given protocol does not exist, it will keep the previously
   * set protocol.
   *
   * @param protocol The protocol name for this URL.
   * @param host The hostname or IP address for this URL.
   * @param port The port number of this URL.
   * @param authority The authority of this URL.
   * @param userInfo The user and password (if needed) of this URL.
   * @param path The "path" portion of this URL.
   * @param query The query of this URL.
   * @param ref The anchor portion of this URL.
   *
   * @since 1.3
   */
  protected void set(String protocol, String host, int port, String authority,
                     String userInfo, String path, String query, String ref)
  {
    URLStreamHandler protocolHandler = null;
    protocol = protocol.toLowerCase();
    if (! this.protocol.equals(protocol))
      protocolHandler = getURLStreamHandler(protocol);
    
    // It is an hidden feature of the JDK. If the protocol does not exist,
    // we keep the previously initialized protocol.
    if (protocolHandler != null)
      {
	this.ph = protocolHandler;
	this.protocol = protocol;
      }
    this.host = host;
    this.userInfo = userInfo;
    this.port = port;
    this.authority = authority;
    if (query == null)
      this.file = path;
    else
      this.file = path + "?" + query;
    this.ref = ref;
    hashCode = hashCode(); // Used for serialization.
  }

  /**
   * Sets the URLStreamHandlerFactory for this class.  This factory is
   * responsible for returning the appropriate protocol handler for
   * a given URL.
   *
   * @param fac The URLStreamHandlerFactory class to use
   *
   * @exception Error If the factory is alread set.
   * @exception SecurityException If a security manager exists and its
   * checkSetFactory method doesn't allow the operation
   */
  public static synchronized void setURLStreamHandlerFactory(URLStreamHandlerFactory fac)
  {
    if (factory != null)
      throw new Error("URLStreamHandlerFactory already set");

    // Throw an exception if an extant security mgr precludes
    // setting the factory.
    SecurityManager s = System.getSecurityManager();
    if (s != null)
      s.checkSetFactory();
    factory = fac;
  }

  /**
   * Returns a String representing this URL.  The String returned is
   * created by calling the protocol handler's toExternalForm() method.
   *
   * @return A string for this URL
   */
  public String toExternalForm()
  {
    // Identical to toString().
    return ph.toExternalForm(this);
  }

  /**
   * Returns a String representing this URL.  Identical to toExternalForm().
   * The value returned is created by the protocol handler's
   * toExternalForm method.  Overrides Object.toString()
   *
   * @return A string for this URL
   */
  public String toString()
  {
    // Identical to toExternalForm().
    return ph.toExternalForm(this);
  }

  /**
   * This internal method is used in two different constructors to load
   * a protocol handler for this URL.
   *
   * @param protocol The protocol to load a handler for
   *
   * @return A URLStreamHandler for this protocol, or null when not found.
   */
  private static synchronized URLStreamHandler getURLStreamHandler(String protocol)
  {
    URLStreamHandler ph = null;

    // First, see if a protocol handler is in our cache.
    if (cache_handlers)
      {
	if ((ph = (URLStreamHandler) ph_cache.get(protocol)) != null)
	  return ph;
      }

    // If a non-default factory has been set, use it to find the protocol.
    if (factory != null)
      {
	ph = factory.createURLStreamHandler(protocol);
      }
    else if (protocol.equals("core"))
      {
 	ph = new gnu.java.net.protocol.core.Handler();
      }
    else if (protocol.equals("file"))
      {
	// This is an interesting case.  It's tempting to think that we
	// could call Class.forName ("gnu.java.net.protocol.file.Handler") to
	// get the appropriate class.  Unfortunately, if we do that the
	// program will never terminate, because getURLStreamHandler is
	// eventually called by Class.forName.
	//
	// Treating "file" as a special case is the minimum that will
	// fix this problem.  If other protocols are required in a
	// statically linked application they will need to be handled in
	// the same way as "file".
	ph = new gnu.java.net.protocol.file.Handler();
      }

    // Non-default factory may have returned null or a factory wasn't set.
    // Use the default search algorithm to find a handler for this protocol.
    if (ph == null)
      {
	// Get the list of packages to check and append our default handler
	// to it, along with the JDK specified default as a last resort.
	// Except in very unusual environments the JDK specified one shouldn't
	// ever be needed (or available).
	String ph_search_path =
	  System.getProperty("java.protocol.handler.pkgs");

	// Tack our default package on at the ends.
	if (ph_search_path != null)
	  ph_search_path += "|" + DEFAULT_SEARCH_PATH;
	else
	  ph_search_path = DEFAULT_SEARCH_PATH;

	// Finally loop through our search path looking for a match.
	StringTokenizer pkgPrefix = new StringTokenizer(ph_search_path, "|");

	// Cache the systemClassLoader
	if (systemClassLoader == null)
	  {
	    systemClassLoader = (ClassLoader) AccessController.doPrivileged
	      (new PrivilegedAction() {
		  public Object run()
	          {
		    return ClassLoader.getSystemClassLoader();
		  }
		});
	  }

	do
	  {
	    try
	      {
		// Try to get a class from the system/application
		// classloader, initialize it, make an instance
		// and try to cast it to a URLStreamHandler.
		String clsName =
		  (pkgPrefix.nextToken() + "." + protocol + ".Handler");
		Class c = Class.forName(clsName, true, systemClassLoader);
		ph = (URLStreamHandler) c.newInstance();
	      }
            catch (ThreadDeath death)
              {
                throw death;
              }
	    catch (Throwable t)
	      {
		// Ignored.
	      }
	  }
	 while (ph == null && pkgPrefix.hasMoreTokens());
      }

    // Update the hashtable with the new protocol handler.
    if (ph != null && cache_handlers)
      ph_cache.put(protocol, ph);
    else
      ph = null;

    return ph;
  }

  private void readObject(ObjectInputStream ois)
    throws IOException, ClassNotFoundException
  {
    ois.defaultReadObject();
    this.ph = getURLStreamHandler(protocol);
    if (this.ph == null)
      throw new IOException("Handler for protocol " + protocol + " not found");
  }

  private void writeObject(ObjectOutputStream oos) throws IOException
  {
    oos.defaultWriteObject();
  }

  /**
   * Returns the equivalent <code>URI</code> object for this <code>URL</code>.
   * This is the same as calling <code>new URI(this.toString())</code>.
   * RFC2396-compliant URLs are guaranteed a successful conversion to
   * a <code>URI</code> instance.  However, there are some values which
   * form valid URLs, but which do not also form RFC2396-compliant URIs.
   *
   * @throws URISyntaxException if this URL is not RFC2396-compliant,
   *         and thus can not be successfully converted to a URI.
   */
  public URI toURI()
    throws URISyntaxException
  {
    return new URI(toString());
  }

}