Java tutorial
/* * Copyright (c) 2002-2015 JGoodies Software GmbH. All Rights Reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * o Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * * o Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * o Neither the name of JGoodies Software GmbH nor the names of * its contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package com.jgoodies.binding.value; import java.beans.PropertyChangeListener; /** * Describes models with a generic access to a single value that allow * to observe value changes. The value can be accessed using the * {@code #getValue()}/{@code #setValue(Object)} methods. * Observers can register instances of {@code PropertyChangeListener} * to be notified if the value changes.<p> * * If the value is read-only or write-only, an implementor may choose * to reject an operation using an {@code UnsupportedOperationException} * or may do nothing or perform an appropriate action, or may return an * appropriate value.<p> * * The listeners registered with this ValueModel using #addValueChangeListener * will be invoked only with PropertyChangeEvents that have the name set to * "value". * In other words, the listeners won't get notified when a PropertyChangeEvent * is fired that has a null object as the name to indicate an arbitrary set * of the event source's properties have changed. This is the case * if you use the PropertyChangeSupport, either directly or indirectly, * to fire property changes with the property name "value" specified. * This constraint ensures that all ValueModel implementors behave * like the AbstractValueModel subclasses. * In the rare case, where you want to notify a PropertyChangeListener * even with PropertyChangeEvents that have no property name set, * you can register the listener with #addPropertyChangeListener, * not #addValueChangeListener.<p> * * AbstractValueModel minimizes the effort required to implement this interface. * It uses the PropertyChangeSupport to fire PropertyChangeEvents, and it adds * PropertyChangeListeners for the specific property name "value". This ensures * that the constraint mentioned above is met.<p> * * Implementors are encouraged to provide non-null values for the * PropertyChangeEvent's old and new values. However, both may be null. * * @author Karsten Lentzsch * @version $Revision: 1.9 $ * * @see AbstractValueModel * @see ValueHolder * @see com.jgoodies.binding.beans.PropertyAdapter */ public interface ValueModel { // Property Names ********************************************************* /** * The name of the bound property <em>value</em>. */ String PROPERTY_VALUE = "value"; // Properties ************************************************************* /** * Returns this model's value. In case of a write-only value, * implementors may choose to either reject this operation or * or return {@code null} or any other appropriate value. * * @return this model's value */ Object getValue(); /** * Sets a new value and notifies any registered value listeners * if the value has changed. In case of a read-only value * implementors may choose to either reject this operation * or to do nothing. * * @param newValue the value to be set */ void setValue(Object newValue); /** * Registers the given PropertyChangeListener with this * ValueModel. The listener will be notified if the value has changed. * The PropertyChangeEvents delivered to the listener must have the name * set to "value". The latter ensures that all ValueModel implementors * behave like the AbstractValueModel subclasses.<p> * * To comply with the above specification implementors can use * the PropertyChangeSupport's #addPropertyChangeListener method * that accepts a property name, so that listeners will be invoked only * if that specific property has changed. * * @param listener the listener to be added * * @see AbstractValueModel#addValueChangeListener(PropertyChangeListener) */ void addValueChangeListener(PropertyChangeListener listener); /** * Deregisters the given PropertyChangeListener from this ValueModel. * * @param listener the listener to be removed */ void removeValueChangeListener(PropertyChangeListener listener); }