001: /*
002: * Copyright (c) 2002-2007 JGoodies Karsten Lentzsch. All Rights Reserved.
003: *
004: * Redistribution and use in source and binary forms, with or without
005: * modification, are permitted provided that the following conditions are met:
006: *
007: * o Redistributions of source code must retain the above copyright notice,
008: * this list of conditions and the following disclaimer.
009: *
010: * o Redistributions in binary form must reproduce the above copyright notice,
011: * this list of conditions and the following disclaimer in the documentation
012: * and/or other materials provided with the distribution.
013: *
014: * o Neither the name of JGoodies Karsten Lentzsch nor the names of
015: * its contributors may be used to endorse or promote products derived
016: * from this software without specific prior written permission.
017: *
018: * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
019: * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
020: * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
021: * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
022: * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
023: * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
024: * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
025: * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
026: * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
027: * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
028: * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029: */
030:
031: package com.jgoodies.binding.value;
032:
033: import java.beans.PropertyChangeListener;
034:
035: /**
036: * Describes models with a generic access to a single value that allow
037: * to observe value changes. The value can be accessed using the
038: * <code>#getValue()</code>/<code>#setValue(Object)</code> methods.
039: * Observers can register instances of <code>PropertyChangeListener</code>
040: * to be notified if the value changes.<p>
041: *
042: * If the value is read-only or write-only, an implementor may choose
043: * to reject an operation using an <code>UnsupportedOperationException</code>
044: * or may do nothing or perform an appropriate action, or may return an
045: * appropriate value.<p>
046: *
047: * The listeners registered with this ValueModel using #addValueChangeListener
048: * will be invoked only with PropertyChangeEvents that have the name set to
049: * "value".
050: * In other words, the listeners won't get notified when a PropertyChangeEvent
051: * is fired that has a null object as the name to indicate an arbitrary set
052: * of the event source's properties have changed. This is the case
053: * if you use the PropertyChangeSupport, either directly or indirectly,
054: * to fire property changes with the property name "value" specified.
055: * This constraint ensures that all ValueModel implementors behave
056: * like the AbstractValueModel subclasses.
057: * In the rare case, where you want to notify a PropertyChangeListener
058: * even with PropertyChangeEvents that have no property name set,
059: * you can register the listener with #addPropertyChangeListener,
060: * not #addValueChangeListener.<p>
061: *
062: * AbstractValueModel minimizes the effort required to implement this interface.
063: * It uses the PropertyChangeSupport to fire PropertyChangeEvents, and it adds
064: * PropertyChangeListeners for the specific property name "value". This ensures
065: * that the constraint mentioned above is met.<p>
066: *
067: * Implementors are encouraged to provide non-null values for the
068: * PropertyChangeEvent's old and new values. However, both may be null.
069: *
070: * @author Karsten Lentzsch
071: * @version $Revision: 1.4 $
072: *
073: * @see AbstractValueModel
074: * @see ValueHolder
075: * @see com.jgoodies.binding.beans.PropertyAdapter
076: */
077: public interface ValueModel {
078:
079: /**
080: * Returns this model's value. In case of a write-only value,
081: * implementors may choose to either reject this operation or
082: * or return <code>null</code> or any other appropriate value.
083: *
084: * @return this model's value
085: */
086: Object getValue();
087:
088: /**
089: * Sets a new value and notifies any registered value listeners
090: * if the value has changed. In case of a read-only value
091: * implementors may choose to either reject this operation
092: * or to do nothing.
093: *
094: * @param newValue the value to be set
095: */
096: void setValue(Object newValue);
097:
098: /**
099: * Registers the given PropertyChangeListener with this
100: * ValueModel. The listener will be notified if the value has changed.
101: * The PropertyChangeEvents delivered to the listener must have the name
102: * set to "value". The latter ensures that all ValueModel implementors
103: * behave like the AbstractValueModel subclasses.<p>
104: *
105: * To comply with the above specification implementors can use
106: * the PropertyChangeSupport's #addPropertyChangeListener method
107: * that accepts a property name, so that listeners will be invoked only
108: * if that specific property has changed.
109: *
110: * @param listener the listener to be added
111: *
112: * @see AbstractValueModel#addValueChangeListener(PropertyChangeListener)
113: */
114: void addValueChangeListener(PropertyChangeListener listener);
115:
116: /**
117: * Deregisters the given PropertyChangeListener from this ValueModel.
118: *
119: * @param listener the listener to be removed
120: */
121: void removeValueChangeListener(PropertyChangeListener listener);
122:
123: }
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