001/* A configurable attribute that replaces any previous instance.
002
003 Copyright (c) 1998-2014 The Regents of the University of California.
004 All rights reserved.
005 Permission is hereby granted, without written agreement and without
006 license or royalty fees, to use, copy, modify, and distribute this
007 software and its documentation for any purpose, provided that the above
008 copyright notice and the following two paragraphs appear in all copies
009 of this software.
010
011 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
012 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
013 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
014 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
015 SUCH DAMAGE.
016
017 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
018 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
019 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
020 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
021 CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
022 ENHANCEMENTS, OR MODIFICATIONS.
023
024 PT_COPYRIGHT_VERSION_2
025 COPYRIGHTENDKEY
026
027 */
028package ptolemy.kernel.util;
029
030///////////////////////////////////////////////////////////////////
031//// SingletonConfigurableAttribute
032
033/**
034 This class is a configurable attribute that replaces any previously
035 existing attribute in the container that has the same name.
036 An important use of this class is to describe icons for visual rendition.
037 The icons are described in an XML schema called SVG, given in the
038 body of a configure XML element.  The icon description is named
039 "_iconDescription", and placing such a description into any container
040 replaces any previous description in the container.
041
042 @author Steve Neuendorffer and Edward A. Lee
043 @version $Id$
044 @since Ptolemy II 1.0
045 @Pt.ProposedRating Green (eal)
046 @Pt.AcceptedRating Green (janneck)
047 */
048public class SingletonConfigurableAttribute extends ConfigurableAttribute
049        implements Singleton {
050    /** Construct a new attribute with no
051     *  container and an empty string as its name. Add the attribute to the
052     *  workspace directory.
053     *  Increment the version number of the workspace.
054     */
055    public SingletonConfigurableAttribute() {
056        super();
057    }
058
059    /** Construct a new attribute with
060     *  no container and an empty string as a name. You can then change
061     *  the name with setName(). If the workspace argument is null, then
062     *  use the default workspace.
063     *  Add the attribute to the workspace directory.
064     *  Increment the version number of the workspace.
065     *  @param workspace The workspace that will list the attribute.
066     */
067    public SingletonConfigurableAttribute(Workspace workspace) {
068        super(workspace);
069    }
070
071    /** Construct an attribute with the given container and name.
072     *  If an attribute already exists with the same name as the one
073     *  specified here, that is an instance of class
074     *  SingletonConfigurableAttribute (or a derived class), then that
075     *  attribute is removed before this one is inserted in the container.
076     *  @param container The container.
077     *  @param name The name of this attribute.
078     *  @exception IllegalActionException If the attribute cannot be contained
079     *   by the proposed container.
080     *  @exception NameDuplicationException If the container already has an
081     *   attribute with this name, and the class of that container is not
082     *   SingletonConfigurableAttribute.
083     */
084    public SingletonConfigurableAttribute(NamedObj container, String name)
085            throws NameDuplicationException, IllegalActionException {
086        super(container, name);
087    }
088
089    ///////////////////////////////////////////////////////////////////
090    ////                         public methods                    ////
091
092    /** Remove any previous attribute in the container that has the same
093     *  name as this attribute, and then call the base class method to set
094     *  the container. If the container is not in the same workspace as
095     *  this attribute, throw an exception.
096     *  If this attribute is already contained by the NamedObj, do nothing.
097     *  If the attribute already has a container, remove
098     *  this attribute from its attribute list first.  Otherwise, remove
099     *  it from the directory of the workspace, if it is there.
100     *  If the argument is null, then remove this attribute from its
101     *  container. It is not added to the workspace directory, so this
102     *  could result in this object being garbage collected.
103     *  <p>
104     *  Note that since an Attribute is a NamedObj, it can itself have
105     *  attributes.  However, recursive containment is not allowed, where
106     *  an attribute is an attribute of itself, or indirectly of any attribute
107     *  it contains.
108     *  <p>
109     *  This method is write-synchronized on the
110     *  workspace and increments its version number.
111     *  @param container The container to attach this attribute to.
112     *  @exception IllegalActionException If this attribute is not of the
113     *   expected class for the container, or it has no name,
114     *   or the attribute and container are not in the same workspace, or
115     *   the proposed container would result in recursive containment.
116     *  @exception NameDuplicationException If the container already has
117     *   an attribute with the name of this attribute that is of class
118     *   SingletonConfigurableAttribute.
119     */
120    @Override
121    public void setContainer(NamedObj container)
122            throws IllegalActionException, NameDuplicationException {
123        Attribute previous = null;
124
125        if (container != null) {
126            previous = container.getAttribute(getName());
127
128            if (previous != null) {
129                previous.setContainer(null);
130            }
131        }
132
133        try {
134            super.setContainer(container);
135        } catch (IllegalActionException ex) {
136            // Restore previous.
137            if (previous != null) {
138                previous.setContainer(container);
139            }
140
141            throw ex;
142        } catch (NameDuplicationException ex) {
143            // Restore previous.
144            if (previous != null) {
145                previous.setContainer(container);
146            }
147
148            throw ex;
149        }
150    }
151}