TransformationPropertyValueModel.java

/*******************************************************************************
 * Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.uitools.app;

import java.beans.PropertyChangeEvent;

import org.eclipse.persistence.tools.workbench.utility.BidiTransformer;


/**
 * A <code>TransformationPropertyValueModel</code> wraps another
 * <code>PropertyValueModel</code> and uses a <code>BidiTransformer</code>
 * to:<ul>
 * <li>transform the wrapped value before it is returned by <code>getValue()</code>
 * <li>"reverse-transform" the new value that comes in via
 * <code>setValue(Object)</code>
 * </ul>
 * As an alternative to building a <code>BidiTransformer</code>,
 * a subclass of <code>TransformationPropertyValueModel</code> can
 * override the <code>transform(Object)</code> and
 * <code>reverseTransform(Object)</code> methods.
 */
public class TransformationPropertyValueModel extends PropertyValueModelWrapper {
    private BidiTransformer transformer;


    // ********** constructors **********

    /**
     * Construct a property value model with the specified nested
     * property value model and a transformer that performs no
     * transformations at all.
     * Use this constructor if you want to override the
     * <code>transform(Object)</code> and <code>reverseTransform(Object)</code>
     * methods instead of building a <code>BidiTransformer</code>.
     */
    public TransformationPropertyValueModel(PropertyValueModel valueHolder) {
        this(valueHolder, BidiTransformer.NULL_INSTANCE);
    }

    /**
     * Construct an property value model with the specified nested
     * property value model and transformer.
     */
    public TransformationPropertyValueModel(PropertyValueModel valueHolder, BidiTransformer transformer) {
        super(valueHolder);
        this.transformer = transformer;
    }


    // ********** ValueModel implementation **********

    /**
     * @see ValueModel#getValue()
     */
    public Object getValue() {
        // transform the object returned by the nested value model before returning it
        return this.transform(this.valueHolder.getValue());
    }


    // ********** PropertyValueModel implementation **********

    /**
     * @see PropertyValueModel#setValue(java.lang.Object)
     */
    public void setValue(Object value) {
        // "reverse-transform" the object before passing it to the the nested value model
        this.valueHolder.setValue(this.reverseTransform(value));
    }


    // ********** PropertyValueModelWrapper implementation **********

    /**
     * @see PropertyValueModelWrapper#valueChanged(java.beans.PropertyChangeEvent)
     */
    protected void valueChanged(PropertyChangeEvent e) {
        // transform the values before propagating the change event
        Object oldValue = this.transform(e.getOldValue());
        Object newValue = this.transform(e.getNewValue());
        this.firePropertyChanged(VALUE, oldValue, newValue);
    }


    // ********** behavior **********

    /**
     * Transform the specified object and return the result.
     * This is called by #getValue().
     */
    protected Object transform(Object value) {
        return this.transformer.transform(value);
    }

    /**
     * "Reverse-transform" the specified object and return the result.
     * This is called by #setValue(Object).
     */
    protected Object reverseTransform(Object value) {
        return this.transformer.reverseTransform(value);
    }

}