IIOMetadataController


1   /*
2    * @(#)IIOMetadataController.java   1.9 03/12/19
3    *
4    * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
5    * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6    */
7   
8   package javax.imageio.metadata;
9   
10  /**
11   * An interface to be implemented by objects that can determine the
12   * settings of an <code>IIOMetadata</code> object, either by putting
13   * up a GUI to obtain values from a user, or by other means.  This
14   * interface merely specifies a generic <code>activate</code> method
15   * that invokes the controller, without regard for how the controller
16   * obtains values (<i>i.e.</i>, whether the controller puts up a GUI
17   * or merely computes a set of values is irrelevant to this
18   * interface).
19   *
20   * <p> Within the <code>activate</code> method, a controller obtains
21   * initial values by querying the <code>IIOMetadata</code> object's
22   * settings, either using the XML DOM tree or a plug-in specific
23   * interface, modifies values by whatever means, then modifies the
24   * <code>IIOMetadata</code> object's settings, using either the
25   * <code>setFromTree</code> or <code>mergeTree</code> methods, or a
26   * plug-in specific interface.  In general, applications may expect
27   * that when the <code>activate</code> method returns
28   * <code>true</code>, the <code>IIOMetadata</code> object is ready for
29   * use in a write operation.
30   *
31   * <p> Vendors may choose to provide GUIs for the
32   * <code>IIOMetadata</code> subclasses they define for a particular
33   * plug-in.  These can be set up as default controllers in the
34   * corresponding <code>IIOMetadata</code> subclasses.
35   *
36   * <p> Alternatively, an algorithmic process such as a database lookup
37   * or the parsing of a command line could be used as a controller, in
38   * which case the <code>activate</code> method would simply look up or
39   * compute the settings, call methods on <code>IIOMetadata</code> to
40   * set its state, and return <code>true</code>.
41   *
42   * @see IIOMetadata#setController
43   * @see IIOMetadata#getController
44   * @see IIOMetadata#getDefaultController
45   * @see IIOMetadata#hasController
46   * @see IIOMetadata#activateController
47   *
48   * @version 0.5
49   */
50  public interface IIOMetadataController {
51  
52      /**
53       * Activates the controller.  If <code>true</code> is returned,
54       * all settings in the <code>IIOMetadata</code> object should be
55       * ready for use in a write operation.  If <code>false</code> is
56       * returned, no settings in the <code>IIOMetadata</code> object
57       * will be disturbed (<i>i.e.</i>, the user canceled the
58       * operation).
59       *
60       * @param metadata the <code>IIOMetadata</code> object to be modified.
61       *
62       * @return <code>true</code> if the <code>IIOMetadata</code> has been
63       * modified, <code>false</code> otherwise.
64       * 
65       * @exception IllegalArgumentException if <code>metadata</code> is
66       * <code>null</code> or is not an instance of the correct class.
67       */
68      boolean activate(IIOMetadata   metadata);
69  }
70
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