/*******************************************************************************
*
* Copyright (c) 2010-2011 Sonatype, Inc.
*
* 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:
*
*
*
*
*******************************************************************************/
package org.hudsonci.utils.marshal.xref;
import org.hudsonci.utils.marshal.Marshaller;
import static com.google.common.base.Preconditions.checkNotNull;
/**
* Reference to an externally serialized entity.
*
* @author <a href="mailto:jason@planet57.com">Jason Dillon</a>
* @since 2.1.0
*/
public abstract class XReference<T> {
protected transient Holder<T> holder;
public XReference(final T value) {
set(value);
}
public XReference() {
// empty
}
public void set(final T value) {
if (value != null) {
holder = new InstanceHolder<T>(value);
}
}
public T get() {
if (holder != null) {
return holder.get();
}
return null;
}
/**
* Defines the path of the external reference.
*/
public abstract String getPath();
/**
* Override to provide alternative marshalling.
*/
public Marshaller getMarshaller() {
return null;
}
@Override
public String toString() {
return getClass().getName() + "{"
+ "holder=" + holder
+ '}';
}
/**
* Provides delegation for instance access.
*/
public static interface Holder<T> {
T get();
}
/**
* Holds on to a specific instance.
*/
public static class InstanceHolder<T>
implements Holder<T> {
protected final T instance;
protected InstanceHolder(final T instance) {
this.instance = checkNotNull(instance);
}
public T get() {
return instance;
}
@Override
public String toString() {
return "InstanceHolder{"
+ "instance=" + instance
+ '}';
}
}
}