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QueryResultSpliterator.java
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QueryResultSpliterator.java
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/**
* Copyright (C) 2022 Czech Technical University in Prague
*
* This program is free software: you can redistribute it and/or modify it under
* the terms of the GNU General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any
* later version.
*
* 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 General Public License for more
* details. You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package cz.cvut.kbss.jopa.model;
import cz.cvut.kbss.jopa.utils.Procedure;
import cz.cvut.kbss.ontodriver.iteration.ResultRow;
import java.util.Optional;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Consumer;
import java.util.function.Function;
/**
* Spliterator for processing {@link cz.cvut.kbss.ontodriver.ResultSet} from {@link cz.cvut.kbss.jopa.model.query.Query} or
* {@link cz.cvut.kbss.jopa.model.query.TypedQuery} stream support.
* <p>
* The main responsibilities of this spliterator are extracting result rows using the specified mapper,
* passing the extraction result to the specified consumer and invoking the {@code onClose} handler once the iteration is finished.
* This handler releases the underlying statement and result set.
*
* @param <X> The type of the extracted item
*/
class QueryResultSpliterator<X> extends Spliterators.AbstractSpliterator<X> {
private final Spliterator<ResultRow> resultSetSpliterator;
private final Function<ResultRow, Optional<X>> mapper;
private final Procedure onClose;
QueryResultSpliterator(Spliterator<ResultRow> resultSetSpliterator, Function<ResultRow, Optional<X>> mapper,
Procedure onClose) {
super(Long.MAX_VALUE, Spliterator.IMMUTABLE | Spliterator.ORDERED | Spliterator.NONNULL);
this.resultSetSpliterator = resultSetSpliterator;
this.mapper = mapper;
this.onClose = onClose;
}
private void mapAndApply(ResultRow row, Consumer<? super X> action) {
mapper.apply(row).ifPresent(action);
}
@Override
public boolean tryAdvance(Consumer<? super X> action) {
try {
final boolean result = resultSetSpliterator.tryAdvance(row -> mapAndApply(row, action));
if (!result) {
onClose.execute();
}
return result;
} catch (RuntimeException e) {
onClose.execute();
throw e;
}
}
@Override
public void forEachRemaining(Consumer<? super X> action) {
try {
resultSetSpliterator.forEachRemaining(row -> mapAndApply(row, action));
} finally {
onClose.execute();
}
}
}