PropertyRef.java

/*******************************************************************************
 * Copyright (c) 2004, 2006
 * Thomas Hallgren, Kenneth Olwing, Mitch Sonies
 * Pontus Rydin, Nils Unden, Peer Torngren
 * The code, documentation and other materials contained herein have been
 * licensed under the Eclipse Public License - v 1.0 by the individual
 * copyright holders listed above, as Initial Contributors under such license.
 * The text of such license is available at www.eclipse.org.
 *******************************************************************************/

package org.eclipse.buckminster.core.common.model;

import java.util.Map;

import org.eclipse.buckminster.core.CorePlugin;
import org.eclipse.buckminster.core.Messages;
import org.eclipse.buckminster.runtime.Trivial;
import org.eclipse.buckminster.sax.Utils;
import org.eclipse.osgi.util.NLS;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.AttributesImpl;

/**
 * An instance of this class represents a reference to a property. The instance
 * will resolve to the expanded value of that property.
 * 
 * @author Thomas Hallgren
 */
public class PropertyRef<T> extends ValueHolder<T> {
	public static final String TAG = "propertyRef"; //$NON-NLS-1$

	public static final String ATTR_KEY = "key"; //$NON-NLS-1$

	private final Class<T> refClass;

	private final String key;

	public PropertyRef(Class<T> refClass, String key) {
		this.key = key;
		this.refClass = refClass;
	}

	@Override
	public T checkedGetValue(Map<String, ? extends Object> properties, int recursionGuard) {
		String expandedKey = ExpandingProperties.expand(properties, key, recursionGuard + 1);
		if (properties instanceof ExpandingProperties<?>)
			return refClass.cast(((ExpandingProperties<?>) properties).getExpandedProperty(expandedKey, recursionGuard + 1));
		final Object replacementValue = properties.get(expandedKey);
		if (replacementValue == null)
			CorePlugin.getLogger().warning(NLS.bind(Messages.The_property_0_has_not_been_set_and_will_default_to_null, key));
		return refClass.cast(ExpandingProperties.expand(properties, replacementValue, recursionGuard + 1));
	}

	@Override
	public boolean equals(Object o) {
		return super.equals(o) && Trivial.equalsAllowNull(key, ((PropertyRef<?>) o).key);
	}

	@Override
	public String getDefaultTag() {
		return TAG;
	}

	@Override
	public int hashCode() {
		int hc = super.hashCode();
		hc = 37 * hc + (key == null ? 0 : key.hashCode());
		return hc;
	}

	@Override
	protected void addAttributes(AttributesImpl attrs) throws SAXException {
		Utils.addAttribute(attrs, ATTR_KEY, key);
	}
}