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Functional style programming with plain JDBC
/*
* Copyright 2016- Anatoly Kutyakov
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package buckelieg.fn.db;
import javax.annotation.Nonnull;
import javax.annotation.ParametersAreNonnullByDefault;
import javax.annotation.concurrent.NotThreadSafe;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
@SuppressWarnings("unchecked")
@NotThreadSafe
@ParametersAreNonnullByDefault
class SelectQuery extends AbstractQuery, PreparedStatement> implements Iterable, Iterator, Spliterator, Select {
ResultSet rs;
private boolean hasNext;
private boolean hasMoved;
private ResultSet wrapper;
SelectQuery(TrySupplier connectionSupplier, String query, Object... params) {
super(connectionSupplier, query, params);
}
@Override
@Nonnull
public final Iterator iterator() {
return this;
}
@Override
public final boolean hasNext() {
if (hasMoved) {
return hasNext;
}
hasNext = doHasNext();
hasMoved = true;
if (!hasNext) {
close();
}
return hasNext;
}
protected boolean doHasNext() {
return jdbcTry(() -> rs != null && rs.next());
}
@Override
public final ResultSet next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
hasMoved = false;
return wrapper;
}
@Nonnull
@Override
public final Stream execute() {
return StreamSupport.stream(jdbcTry(() -> {
doExecute();
if (rs != null) {
wrapper = new ImmutableResultSet(rs);
}
return this;
}), false).onClose(this::close);
}
protected void doExecute() {
withStatement(s -> rs = s.executeQuery());
}
@Nonnull
@Override
public final Select fetchSize(int size) {
return setStatementParameter(s -> s.setFetchSize(size > 0 ? size : 0)); // 0 value is ignored by ResultSet.setFetchSize;
}
@Nonnull
@Override
public final Select maxRows(int max) {
return setStatementParameter(s -> s.setMaxRows(max > 0 ? max : 0));
}
@Nonnull
@Override
public final Select maxRows(long max) {
return setStatementParameter(s -> s.setLargeMaxRows(max > 0 ? max : 0));
}
@Nonnull
@Override
public final Select poolable(boolean poolable) {
return setPoolable(poolable);
}
@Nonnull
@Override
public final Select timeout(int timeout) {
return setTimeout(timeout);
}
@Nonnull
@Override
public final Select escaped(boolean escapeProcessing) {
return setEscapeProcessing(escapeProcessing);
}
@Nonnull
@Override
public Select print(Consumer printer) {
return log(printer);
}
@Override
public final Spliterator spliterator() {
return this;
}
@Override
public final boolean tryAdvance(Consumer action) {
if (hasNext()) {
Objects.requireNonNull(action).accept(next());
return true;
}
return false;
}
@Override
public final Spliterator trySplit() {
return null; // not splittable. Parallel streams would not gain any performance benefits.
}
@Override
public final long estimateSize() {
return Long.MAX_VALUE;
}
@Override
public final int characteristics() {
return Spliterator.IMMUTABLE | Spliterator.ORDERED | Spliterator.NONNULL;
}
@Override
public void forEachRemaining(Consumer action) {
while (tryAdvance(action)) {
}
}
@Override
PreparedStatement prepareStatement(TrySupplier connectionSupplier, String query, Object... params) {
return jdbcTry(() -> setQueryParameters(connectionSupplier.get().prepareStatement(query), params));
}
}