com.jgoodies.binding.extras.NonNullValueModel Maven / Gradle / Ivy
Show all versions of jgoodies-binding Show documentation
/*
* Copyright (c) 2002-2013 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.extras;
import static com.jgoodies.common.base.Preconditions.checkNotNull;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import com.jgoodies.binding.value.AbstractValueModel;
import com.jgoodies.binding.value.ValueModel;
/**
* A {@link ValueModel} implementation that avoids {@code null} values.
* It wraps another ValueModel and returns a (non-null) default value
* if the wrapped ValueModel returns null.
*
* Note that value change events fired by this model may use null
* as old and/or new value. This is because PropertyChangeEvents use null
* to indicate that the old and/or new value is not provided by the event.
*
* Note: This class is not yet part of the binary Binding
* library; it comes with the Binding distributions as an extra.
* The API is work in progress and may change without notice;
* this class may even be completely removed from future distributions.
* If you want to use this class, you may consider copying it into
* your code base.
*
* @author Karsten Lentzsch
* @version $Revision: 1.10 $
*
* @since 1.1
*/
public final class NonNullValueModel extends AbstractValueModel {
/**
* Holds the wrapped subject ValueModel.
*/
private final ValueModel subject;
/**
* The value returned by this model whenever the
* underlying (wrapped) ValueModel returns {@code null}.
*/
private final Object defaultValue;
// Instance Creation ******************************************************
/**
* Constructs an NonNullValueModel for the given ValueModel.
*
* @param subject the underlying (or wrapped) ValueModel
* @param defaultValue the value used whenever the wrapped model
* returns {@code null}
*
* @throws NullPointerException if the subject or defaultValue is {@code null}
*/
public NonNullValueModel(ValueModel subject, Object defaultValue) {
this.subject = subject;
this.defaultValue = checkNotNull(defaultValue, "The default value must not be null.");
subject.addValueChangeListener(new SubjectValueChangeHandler());
}
// ValueModel Implementation **********************************************
/**
* Returns this model's current subject value.
*
* @return this model's current subject value.
*/
@Override
public Object getValue() {
Object subjectValue = subject.getValue();
return subjectValue != null
? subjectValue
: defaultValue;
}
/**
* Sets the given value to the wrapped ValueModel.
* The value set can be {@code null}.
*
* @param newValue the value to set
*/
@Override
public void setValue(Object newValue) {
subject.setValue(newValue);
}
// Event Handling *********************************************************
/**
* Forwards value changes in the subject to listeners of this model.
* We don't use the default value if the old and/or new value is null.
* This is because null has a different meaning in PropertyChangeEvents:
* it indicates that the value is not available.
*/
private final class SubjectValueChangeHandler implements PropertyChangeListener {
@Override
public void propertyChange(PropertyChangeEvent evt) {
fireValueChange(evt.getOldValue(), evt.getNewValue(), true);
}
}
}