HHH-6333 - Create DeferredInitializationValue
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/*
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* Hibernate, Relational Persistence for Idiomatic Java
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*
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* Copyright (c) 2011, Red Hat Inc. or third-party contributors as
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* indicated by the @author tags or express copyright attribution
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* statements applied by the authors. All third-party contributions are
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* distributed under license by Red Hat Inc.
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*
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* This copyrighted material is made available to anyone wishing to use, modify,
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* copy, or redistribute it subject to the terms and conditions of the GNU
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* Lesser General Public License, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
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* for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this distribution; if not, write to:
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* Free Software Foundation, Inc.
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* 51 Franklin Street, Fifth Floor
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* Boston, MA 02110-1301 USA
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*/
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package org.hibernate.internal.util;
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/**
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* Represents a "final" value that is initialized either {@link #Value(Object) up front} or once at some point
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* {@link #Value(org.hibernate.internal.util.Value.DeferredInitializer) after} declaration.
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*
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* @author Steve Ebersole
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*/
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public class Value<T> {
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/**
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* The snippet that generates the initialization value.
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*
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* @param <T>
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*/
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public static interface DeferredInitializer<T> {
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/**
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* Build the initialization value.
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* <p/>
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* Implementation note: returning {@code null} is "ok" but will cause this method to keep being called.
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*
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* @return The initialization value.
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*/
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public T initialize();
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}
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private final DeferredInitializer<T> valueInitializer;
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private T value;
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/**
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* Instantiates a {@link Value} with the specified initializer.
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*
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* @param valueInitializer The initializer to use in {@link #getValue} when value not yet known.
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*/
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public Value(DeferredInitializer<T> valueInitializer) {
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this.valueInitializer = valueInitializer;
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}
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@SuppressWarnings( {"unchecked"})
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public Value(T value) {
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this( NO_DEFERRED_INITIALIZER );
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this.value = value;
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}
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public T getValue() {
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if ( value == null ) {
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value = valueInitializer.initialize();
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}
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return value;
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}
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private static final DeferredInitializer NO_DEFERRED_INITIALIZER = new DeferredInitializer() {
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@Override
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public Void initialize() {
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return null;
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}
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};
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}
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