001/* A parameter that is a singleton.
002
003 Copyright (c) 2003-2016 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
028 */
029package ptolemy.data.expr;
030
031import ptolemy.kernel.util.Attribute;
032import ptolemy.kernel.util.IllegalActionException;
033import ptolemy.kernel.util.NameDuplicationException;
034import ptolemy.kernel.util.NamedObj;
035
036///////////////////////////////////////////////////////////////////
037//// SingletonParameter
038
039/**
040 This subclass of Parameter is identical to Parameter except that it
041 is a singleton, meaning that when its container is set, if the container
042 already contains an attribute with the same name, then that attribute
043 is first removed.
044
045 @author Edward A. Lee
046 @version $Id$
047 @since Ptolemy II 4.0
048 @Pt.ProposedRating Yellow (eal)
049 @Pt.AcceptedRating Red (cxh)
050 */
051public class SingletonParameter extends Parameter {
052    /** Construct a parameter with the given name contained by the specified
053     *  entity. The container argument must not be null, or a
054     *  NullPointerException will be thrown.  This parameter will use the
055     *  workspace of the container for synchronization and version counts.
056     *  If the name argument is null, then the name is set to the empty string.
057     *  The object is not added to the list of objects in the workspace
058     *  unless the container is null.
059     *  Increment the version of the workspace.
060     *  @param container The container.
061     *  @param name The name of the parameter.
062     *  @exception IllegalActionException If the parameter is not of an
063     *   acceptable class for the container.
064     *  @exception NameDuplicationException If the name coincides with
065     *   a parameter already in the container.
066     */
067    public SingletonParameter(NamedObj container, String name)
068            throws IllegalActionException, NameDuplicationException {
069        super(container, name);
070    }
071
072    /** Construct a Parameter with the given container, name, and Token.
073     *  The container argument must not be null, or a
074     *  NullPointerException will be thrown.  This parameter will use the
075     *  workspace of the container for synchronization and version counts.
076     *  If the name argument is null, then the name is set to the empty string.
077     *  The object is not added to the list of objects in the workspace
078     *  unless the container is null.
079     *  Increment the version of the workspace.
080     *  If the name argument is null, then the name is set to the empty
081     *  string.
082     *  @param container The container.
083     *  @param name The name.
084     *  @param token The Token contained by this Parameter.
085     *  @exception IllegalActionException If the parameter is not of an
086     *   acceptable class for the container.
087     *  @exception NameDuplicationException If the name coincides with
088     *   an parameter already in the container.
089     */
090    public SingletonParameter(NamedObj container, String name,
091            ptolemy.data.Token token)
092            throws IllegalActionException, NameDuplicationException {
093        super(container, name, token);
094    }
095
096    ///////////////////////////////////////////////////////////////////
097    ////                         public methods                    ////
098
099    /** Remove any previous attribute in the container that has the same
100     *  name as this attribute, and then call the base class method to set
101     *  the container. If the container is not in the same workspace as
102     *  this attribute, throw an exception.
103     *  If this attribute is already contained by the NamedObj, do nothing.
104     *  If the attribute already has a container, remove
105     *  this attribute from its attribute list first.  Otherwise, remove
106     *  it from the directory of the workspace, if it is there.
107     *  If the argument is null, then remove this attribute from its
108     *  container. It is not added to the workspace directory, so this
109     *  could result in this object being garbage collected.
110     *  <p>
111     *  This method is write-synchronized on the
112     *  workspace and increments its version number.
113     *  @param container The container to attach this attribute to.
114     *  @exception IllegalActionException If this attribute is not of the
115     *   expected class for the container, or it has no name,
116     *   or the attribute and container are not in the same workspace, or
117     *   the proposed container would result in recursive containment.
118     *  @exception NameDuplicationException If the container already has
119     *   an attribute with the name of this attribute that is of class
120     *   SingletonConfigurableAttribute.
121     */
122    @Override
123    public void setContainer(NamedObj container)
124            throws IllegalActionException, NameDuplicationException {
125        Attribute previous = null;
126
127        if (container != null) {
128            previous = container.getAttribute(getName());
129
130            if (previous != null) {
131                previous.setContainer(null);
132            }
133        }
134
135        try {
136            super.setContainer(container);
137        } catch (IllegalActionException ex) {
138            // Restore previous.
139            if (previous != null) {
140                previous.setContainer(container);
141            }
142
143            throw ex;
144        } catch (NameDuplicationException ex) {
145            // Restore previous.
146            if (previous != null) {
147                previous.setContainer(container);
148            }
149
150            throw ex;
151        }
152    }
153}