001/*
002 * #%L
003 * HAPI FHIR JPA Server
004 * %%
005 * Copyright (C) 2014 - 2024 Smile CDR, Inc.
006 * %%
007 * Licensed under the Apache License, Version 2.0 (the "License");
008 * you may not use this file except in compliance with the License.
009 * You may obtain a copy of the License at
010 *
011 * http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 * #L%
019 */
020package ca.uhn.fhir.jpa.util;
021
022import org.apache.commons.lang3.Validate;
023import org.hibernate.ScrollableResults;
024
025import java.io.Closeable;
026import java.util.Iterator;
027
028public class ScrollableResultsIterator<T extends Object> extends BaseIterator<T> implements Iterator<T>, Closeable {
029        private boolean hasNext;
030        private T myNext;
031        private ScrollableResults myScroll;
032
033        public ScrollableResultsIterator(ScrollableResults theScroll) {
034                myScroll = theScroll;
035        }
036
037        @SuppressWarnings("unchecked")
038        private void ensureHaveNext() {
039                if (myNext == null) {
040                        if (myScroll.next()) {
041                                hasNext = true;
042                                myNext = (T) myScroll.get();
043                        } else {
044                                hasNext = false;
045                        }
046                }
047        }
048
049        @Override
050        public boolean hasNext() {
051                ensureHaveNext();
052                return hasNext;
053        }
054
055        @Override
056        public T next() {
057                ensureHaveNext();
058                Validate.isTrue(hasNext);
059                T next = myNext;
060                myNext = null;
061                return next;
062        }
063
064        @Override
065        public void close() {
066                if (myScroll != null) {
067                        myScroll.close();
068                        myScroll = null;
069                }
070        }
071}