com.jgoodies.binding.value.AbstractConverter Maven / Gradle / Ivy
/*
* Copyright (c) 2002-2012 JGoodies Karsten Lentzsch. 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 Karsten Lentzsch 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;
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* 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.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
/**
* An abstract class that minimizes the effort required to implement
* a type converter. A type converter is a ValueModel that converts the type
* of an object being held as a value in one ValueModel into another type.
*
* More formally, a converting ValueModel VM1 converts the type
* T2 of an object being held as a value in one ValueModel VM2
* into another type T1. When reading a value from VM1,
* instances of T2 are read from VM2 and are converted to T1. When storing
* a new value to VM1, the type converter will perform the inverse conversion
* and will convert an instance of T1 to T2.
*
* The conversion must be performed when reading and writing values,
* as well as in the change notification. This class specifies abstract
* methods for the conversion from source to output, which is used to
* convert in {@code #getValue} and in the change notification.
* For the write conversion you must implement {@code #setValue}.
*
* Most converters can set values converted by {@code #convertFromSubject}
* with {@code #setValue}. However, a converter may reject subject values
* to be converted and may reject values to be set - as any ValueModel.
*
* Type converters should be used judiciously and only to bridge two
* {@code ValueModel}s. Converters often use a generic but weak
* conversion, and so can be limited w.r.t. to localized
* formatting conventions.
*
* When binding non-String values to a text UI component, consider
* using a {@link javax.swing.JFormattedTextField}. Formatted text fields
* provide a powerful means to convert strings to objects and handle many cases
* that arise around invalid input. Formatted text fields can be bound
* to {@code ValueModel}s using the
* {@link com.jgoodies.binding.beans.PropertyConnector} class.
*
*
* @author Karsten Lentzsch
* @version $Revision: 1.15 $
*
* @see ValueModel
* @see ConverterFactory
* @see javax.swing.JFormattedTextField
* @see com.jgoodies.binding.beans.PropertyConnector
*
* @deprecated Replaced by the {@link BindingConverter} interface
* and - if necessary - the {@link ConverterValueModel}
*/
@Deprecated
public abstract class AbstractConverter extends AbstractWrappedValueModel {
/**
* Holds the ValueModel that in turn holds the source value.
*/
protected final ValueModel subject;
// Instance creation ******************************************************
/**
* Constructs an AbstractConverter on the given subject.
*
* @param subject the ValueModel that holds the source value
* @throws NullPointerException if the subject is {@code null}
*/
public AbstractConverter(ValueModel subject) {
super(subject);
this.subject = subject;
}
// Abstract Behavior ******************************************************
/**
* Converts a value from the subject to the type or format used
* by this converter.
*
* @param subjectValue the subject's value
* @return the converted value in the type or format used by this converter
*/
public abstract Object convertFromSubject(Object subjectValue);
// ValueModel Implementation **********************************************
/**
* Converts the subject's value and returns the converted value.
*
* @return the converted subject value
*/
@Override
public Object getValue() {
return convertFromSubject(subject.getValue());
}
// AbstractWrappedValueModel Behavior *************************************
@Override
protected PropertyChangeListener createValueChangeHandler() {
return new ValueChangeHandler();
}
// Helper Class ***********************************************************
/**
* Listens to value changes in the wrapped model, converts the old and
* new value - if any - and fires a value change for this converter.
*/
private final class ValueChangeHandler implements PropertyChangeListener {
/**
* Notifies listeners about a change in the underlying subject.
* The old and new value used in the PropertyChangeEvent to be fired
* are converted versions of the observed old and new values.
* The observed old and new value are converted only
* if they are non-null. This is because {@code null}
* may be a valid value or may indicate not available.
*
* TODO: We may need to check the identity, not equity.
*
* @param evt the property change event to be handled
*/
@Override
public void propertyChange(PropertyChangeEvent evt) {
Object convertedOldValue = evt.getOldValue() == null
? null
: convertFromSubject(evt.getOldValue());
Object convertedNewValue = evt.getNewValue() == null
? null
: convertFromSubject(evt.getNewValue());
fireValueChange(convertedOldValue, convertedNewValue);
}
}
}