/*******************************************************************************
* Copyright (c) 2007, 2009 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0, which accompanies this distribution
* and is available at http://www.eclipse.org/legal/epl-v10.html.
*
* Contributors:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.utility.internal.model.value;
import org.eclipse.jpt.utility.Filter;
import org.eclipse.jpt.utility.model.event.PropertyChangeEvent;
import org.eclipse.jpt.utility.model.value.PropertyValueModel;
/**
* A <code>FilteringPropertyValueModel</code> wraps another
* {@link PropertyValueModel} and uses a {@link Filter}
* to determine when the wrapped value is to be returned by calls
* to {@link #getValue()}.
* <p>
* As an alternative to building a {@link Filter}, a subclass
* can override {@link #accept(T)}.
* <p>
* One, possibly undesirable, side-effect of using this value model is that
* it must return *something* as the value. The default behavior is
* to return <code>null</code> whenever the wrapped value is not "accepted",
* which can be configured and/or overridden ({@link #getDefaultValue()}).
*/
public class FilteringPropertyValueModel<T>
extends PropertyValueModelWrapper<T>
implements PropertyValueModel<T>
{
protected final Filter<T> filter;
protected final T defaultValue;
// ********** constructors **********
/**
* Construct a filtering property value model with the specified nested
* property value model and a disabled filter.
* Use this constructor if you want to override {@link #accept(T)}
* instead of building a {@link Filter}.
* The default value will be <code>null</code>.
*/
public FilteringPropertyValueModel(PropertyValueModel<? extends T> valueHolder) {
this(valueHolder, Filter.Disabled.<T>instance(), null);
}
/**
* Construct a filtering property value model with the specified nested
* property value model, specified default value, and a disabled filter.
* Use this constructor if you want to override {@link #accept(T)}
* instead of building a {@link Filter}
* <em>and</em> you need to specify
* a default value other than <code>null</code>.
*/
public FilteringPropertyValueModel(PropertyValueModel<? extends T> valueHolder, T defaultValue) {
this(valueHolder, Filter.Disabled.<T>instance(), defaultValue);
}
/**
* Construct a filtering property value model with the specified nested
* property value model and filter.
* The default value will be <code>null</code>.
*/
public FilteringPropertyValueModel(PropertyValueModel<? extends T> valueHolder, Filter<T> filter) {
this(valueHolder, filter, null);
}
/**
* Construct a filtering property value model with the specified nested
* property value model, filter, and default value.
*/
public FilteringPropertyValueModel(PropertyValueModel<? extends T> valueHolder, Filter<T> filter, T defaultValue) {
super(valueHolder);
this.filter = filter;
this.defaultValue = defaultValue;
}
// ********** PropertyValueModel implementation **********
public T getValue() {
return this.filterValue(this.valueHolder.getValue());
}
// ********** PropertyValueModelWrapper implementation **********
@Override
protected void valueChanged(PropertyChangeEvent event) {
// filter the values before propagating the change event
@SuppressWarnings("unchecked")
T eventOldValue = (T) event.getOldValue();
Object oldValue = this.filterValue(eventOldValue);
@SuppressWarnings("unchecked")
T eventNewValue = (T) event.getNewValue();
Object newValue = this.filterValue(eventNewValue);
this.firePropertyChanged(VALUE, oldValue, newValue);
}
// ********** queries **********
/**
* If the specified value is "accepted" simply return it,
* otherwise return the default value.
*/
protected T filterValue(T value) {
return this.accept(value) ? value : this.getDefaultValue();
}
/**
* Return whether the filtering property value model should
* return the specified value from a call to
* {@link #getValue()}; the value came
* from the nested property value model
* <p>
* This method can be overridden by a subclass as an
* alternative to building a {@link Filter}.
*/
protected boolean accept(T value) {
return this.filter.accept(value);
}
/**
* Return the object that should be returned if
* the nested value was rejected by the filter.
* The default is <code>null</code>.
*/
protected T getDefaultValue() {
return this.defaultValue;
}
@Override
public void toString(StringBuilder sb) {
sb.append(this.getValue());
}
}
