urlconnection.java

gcc的组建

   * @param defaultValue The default date if the header field is not found
   * or can't be converted.
   *
   * @return Returns the date value of the header filed or the default value
   * if the field is missing or malformed
   */
  public long getHeaderFieldDate(String name, long defaultValue)
  {
    if (! dateformats_initialized)
      initializeDateFormats();

    if (position == null)
      position = new ParsePosition(0);

    long result = defaultValue;
    String str = getHeaderField(name);

    if (str != null)
      {
	for (int i = 0; i < dateFormats.length; i++)
	  {
	    SimpleDateFormat df = dateFormats[i];
	    position.setIndex(0);
	    position.setErrorIndex(0);
	    Date date = df.parse(str, position);
	    if (date != null)
	      return date.getTime();
	  }
      }

    return result;
  }

  /**
   * Returns a String representing the header key at the specified index.
   * This allows the caller to walk the list of header fields.  The analogous
   * getHeaderField(int) method allows access to the corresponding value for
   * this tag.
   *
   * @param index The index into the header field list to retrieve the key for.
   *
   * @return The header field key or null if index is past the end
   * of the headers.
   */
  public String getHeaderFieldKey(int index)
  {
    // Subclasses for specific protocols override this.
    return null;
  }

  /**
   * This method returns the content of the document pointed to by the
   * URL as an Object.  The type of object depends on the MIME type of
   * the object and particular content hander loaded.  Most text type
   * content handlers will return a subclass of
   * <code>InputStream</code>.  Images usually return a class that
   * implements <code>ImageProducer</code>.  There is not guarantee
   * what type of object will be returned, however.
   *
   * <p>This class first determines the MIME type of the content, then
   * creates a ContentHandler object to process the input.  If the
   * <code>ContentHandlerFactory</code> is set, then that object is
   * called to load a content handler, otherwise a class called
   * gnu.java.net.content.&lt;content_type&gt; is tried.  If this
   * handler does not exist, the method will simple return the
   * <code>InputStream</code> returned by
   * <code>getInputStream()</code>.  Note that the default
   * implementation of <code>getInputStream()</code> throws a
   * <code>UnknownServiceException</code> so subclasses are encouraged
   * to override this method.</p>
   *
   * @return the content
   *
   * @exception IOException If an error with the connection occurs.
   * @exception UnknownServiceException If the protocol does not support the
   * content type at all.
   */
  public Object getContent() throws IOException
  {
    if (!connected)
      connect();

    // FIXME: Doc indicates that other criteria should be applied as
    // heuristics to determine the true content type, e.g. see 
    // guessContentTypeFromName() and guessContentTypeFromStream methods
    // as well as FileNameMap class & fileNameMap field & get/set methods.
    String type = getContentType();
    ContentHandler ch = getContentHandler(type);

    if (ch != null)
      return ch.getContent(this);

    return getInputStream();
  }

  /**
   * Retrieves the content of this URLConnection
   *
   * @param classes The allowed classes for the content
   *
   * @return the content
   *
   * @exception IOException If an error occurs
   * @exception UnknownServiceException If the protocol does not support the
   * content type
   */
  public Object getContent(Class[] classes) throws IOException
  {
    // FIXME: implement this
    return getContent();
  }

  /**
   * This method returns a <code>Permission</code> object representing the
   * permissions required to access this URL.  This method returns
   * <code>java.security.AllPermission</code> by default.  Subclasses should
   * override it to return a more specific permission.  For example, an
   * HTTP URL should return an instance of <code>SocketPermission</code>
   * for the appropriate host and port.
   * <p>
   * Note that because of items such as HTTP redirects, the permission
   * object returned might be different before and after connecting.
   *
   * @return A Permission object
   *
   * @exception IOException If the computation of the permission requires
   * network or file I/O and an exception occurs while computing it
   */
  public Permission getPermission() throws IOException
  {
    // Subclasses may override this.
    return new AllPermission();
  }

  /**
   * Returns an InputStream for this connection.  As this default
   * implementation returns null, subclasses should override this method
   *
   * @return An InputStream for this connection
   *
   * @exception IOException If an error occurs
   * @exception UnknownServiceException If the protocol does not support input
   */
  public InputStream getInputStream() throws IOException
  {
    // Subclasses for specific protocols override this.
    throw new UnknownServiceException("Protocol " + url.getProtocol()
                                      + " does not support input.");
  }

  /**
   * Returns an OutputStream for this connection.  As this default
   * implementation returns null, subclasses should override this method
   *
   * @return An OutputStream for this connection
   *
   * @exception IOException If an error occurs
   * @exception UnknownServiceException If the protocol does not support output
   */
  public OutputStream getOutputStream() throws IOException
  {
    // Subclasses for specific protocols override this.
    throw new UnknownServiceException("Protocol " + url.getProtocol()
                                      + " does not support output.");
  }

  /**
   * The methods prints the value of this object as a String by calling the
   * toString() method of its associated URL.  Overrides Object.toString()
   *
   * @return A String representation of this object
   */
  public String toString()
  {
    return this.getClass().getName() + ":" + url.toString();
  }

  /**
   * Sets the value of a flag indicating whether or not input is going
   * to be done for this connection.  This default to true unless the
   * doOutput flag is set to false, in which case this defaults to false.
   *
   * @param input <code>true</code> if input is to be done,
   * <code>false</code> otherwise
   *
   * @exception IllegalStateException If already connected
   */
  public void setDoInput(boolean input)
  {
    if (connected)
      throw new IllegalStateException("Already connected");

    doInput = input;
  }

  /**
   * Returns the value of a flag indicating whether or not input is going
   * to be done for this connection.  This default to true unless the
   * doOutput flag is set to false, in which case this defaults to false.
   *
   * @return true if input is to be done, false otherwise
   */
  public boolean getDoInput()
  {
    return doInput;
  }

  /**
   * Sets a boolean flag indicating whether or not output will be done
   * on this connection.  The default value is false, so this method can
   * be used to override the default
   *
   * @param output ture if output is to be done, false otherwise
   *
   * @exception IllegalStateException If already connected
   */
  public void setDoOutput(boolean output)
  {
    if (connected)
      throw new IllegalStateException("Already connected");

    doOutput = output;
  }

  /**
   * Returns a boolean flag indicating whether or not output will be done
   * on this connection.  This defaults to false.
   *
   * @return true if output is to be done, false otherwise
   */
  public boolean getDoOutput()
  {
    return doOutput;
  }

  /**
   * Sets a boolean flag indicating whether or not user interaction is
   * allowed for this connection.  (For example, in order to prompt for
   * username and password info.
   *
   * @param allow true if user interaction should be allowed, false otherwise.
   *
   * @exception IllegalStateException If already connected
   */
  public void setAllowUserInteraction(boolean allow)
  {
    allowUserInteraction = allow;
  }

  /**
   * Returns a boolean flag indicating whether or not user interaction is
   * allowed for this connection.  (For example, in order to prompt for
   * username and password info.
   *
   * @return true if user interaction is allowed, false otherwise
   */
  public boolean getAllowUserInteraction()
  {
    return allowUserInteraction;
  }

  /**
   * Sets the default flag for whether or not interaction with a user
   * is allowed.  This will be used for all connections unless overridden
   *
   * @param allow true to allow user interaction, false otherwise
   */
  public static void setDefaultAllowUserInteraction(boolean allow)
  {
    defaultAllowUserInteraction = allow;
  }

  /**
   * Returns the default flag for whether or not interaction with a user
   * is allowed.  This will be used for all connections unless overridden
   *
   * @return true if user interaction is allowed, false otherwise
   */
  public static boolean getDefaultAllowUserInteraction()
  {
    return defaultAllowUserInteraction;
  }

  /**
   * Sets a boolean flag indicating whether or not caching will be used
   * (if possible) to store data downloaded via the connection.
   *
   * @param usecaches The new value
   *
   * @exception IllegalStateException If already connected
   */
  public void setUseCaches(boolean usecaches)
  {
    if (connected)
      throw new IllegalStateException("Already connected");

    useCaches = usecaches;
  }

  /**
   * Returns a boolean flag indicating whether or not caching will be used
   * (if possible) to store data downloaded via the connection.
   *
   * @return true if caching should be used if possible, false otherwise
   */
  public boolean getUseCaches()
  {
    return useCaches;
  }

  /**
   * Sets the ifModified since instance variable.  If this value is non
   * zero and the underlying protocol supports it, the actual document will
   * not be fetched unless it has been modified since this time.  The value
   * passed should  be 0 if this feature is to be disabled or the time expressed
   * as the number of seconds since midnight 1/1/1970 GMT otherwise.
   *
   * @param ifmodifiedsince The new value in milliseconds
   * since January 1, 1970 GMT
   *
   * @exception IllegalStateException If already connected
   */
  public void setIfModifiedSince(long ifmodifiedsince)
  {
    if (connected)
      throw new IllegalStateException("Already connected");

    ifModifiedSince = ifmodifiedsince;
  }

  /**
   * Returns the ifModified since instance variable.  If this value is non
   * zero and the underlying protocol supports it, the actual document will
   * not be fetched unless it has been modified since this time.  The value
   * returned will be 0 if this feature is disabled or the time expressed
   * as the number of seconds since midnight 1/1/1970 GMT otherwise
   *
   * @return The ifModifiedSince value
   */
  public long getIfModifiedSince()
  {
    return ifModifiedSince;
  }

  /**
   * Returns the default value used to determine whether or not caching
   * of documents will be done when possible.
   *
   * @return true if caches will be used, false otherwise
   */
  public boolean getDefaultUseCaches()
  {
    return defaultUseCaches;
  }

  /**
   * Sets the default value used to determine whether or not caching
   * of documents will be done when possible.
   *
   * @param use true to use caches if possible by default, false otherwise
   */
  public void setDefaultUseCaches(boolean use)
  {