/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2011, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.internal.util;
/**
* Represents a "final" value that is initialized either {@link #Value(Object) up front} or once at some point
* {@link #Value(org.hibernate.internal.util.Value.DeferredInitializer) after} declaration.
*
* @author Steve Ebersole
*/
public class Value<T> {
/**
* The snippet that generates the initialization value.
*
* @param <T>
*/
public static interface DeferredInitializer<T> {
/**
* Build the initialization value.
* <p/>
* Implementation note: returning {@code null} is "ok" but will cause this method to keep being called.
*
* @return The initialization value.
*/
public T initialize();
}
private final DeferredInitializer<T> valueInitializer;
private T value;
/**
* Instantiates a {@link Value} with the specified initializer.
*
* @param valueInitializer The initializer to use in {@link #getValue} when value not yet known.
*/
public Value(DeferredInitializer<T> valueInitializer) {
this.valueInitializer = valueInitializer;
}
@SuppressWarnings( {"unchecked"})
public Value(T value) {
this( NO_DEFERRED_INITIALIZER );
this.value = value;
}
public T getValue() {
if ( value == null ) {
value = valueInitializer.initialize();
}
return value;
}
private static final DeferredInitializer NO_DEFERRED_INITIALIZER = new DeferredInitializer() {
@Override
public Void initialize() {
return null;
}
};
}