buckelieg.simpletools.db.SelectQuery Maven / Gradle / Ivy
/*
* 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.simpletools.db;
import org.apache.log4j.Logger;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.ParametersAreNonnullByDefault;
import javax.annotation.concurrent.NotThreadSafe;
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.concurrent.atomic.AtomicBoolean;
import java.util.function.Consumer;
@NotThreadSafe
@ParametersAreNonnullByDefault
class SelectQuery implements Iterable, Iterator, Spliterator, Select {
private static final Logger LOG = Logger.getLogger(SelectQuery.class);
final S statement;
private final AtomicBoolean hasNext;
private final AtomicBoolean hasMoved;
ResultSet rs;
private ImmutableResultSet wrapper;
private int batchSize = -1;
SelectQuery(S statement) {
this.statement = Objects.requireNonNull(statement, "Statement must not be null");
this.hasMoved = new AtomicBoolean();
this.hasNext = new AtomicBoolean();
}
@Override
public final Iterator iterator() {
return this;
}
@Override
public final boolean hasNext() {
try {
if (hasMoved.get()) {
return hasNext.get();
}
hasNext.set(doHasNext());
hasMoved.set(true);
} catch (SQLException e) {
hasNext.set(false);
}
if (!hasNext.get()) {
close();
}
return hasNext.get();
}
protected boolean doHasNext() throws SQLException {
return rs != null && rs.next();
}
@Override
public final ResultSet next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
hasMoved.set(false);
return wrapper;
}
@Nullable
@Override
public final T single(Try._1 mapper) {
try {
return Objects.requireNonNull(mapper, "Mapper must be provided").doTry(execute().iterator().next());
} catch (SQLException | NoSuchElementException e) {
throw new SQLRuntimeException(e);
} finally {
close();
}
}
@Nonnull
@Override
public final Iterable execute() {
try {
if (batchSize >= 0) {
statement.setFetchSize(batchSize);
}
doExecute();
if (rs != null) {
this.wrapper = new ImmutableResultSet(rs);
}
} catch (SQLException e) {
throw new SQLRuntimeException(e);
}
return this;
}
protected void doExecute() throws SQLException {
this.rs = statement.executeQuery();
}
@Nonnull
@Override
public final Select batchSize(int size) {
try {
batchSize = rs != null && rs.getFetchSize() >= size ? rs.getFetchSize() : size > 0 ? size : 0; // 0 value is ignored by ResultSet.setFetchSize
} catch (SQLException e) {
throw new SQLRuntimeException(e);
}
return this;
}
@Override
public final Spliterator spliterator() {
return this;
}
@Override
public final boolean tryAdvance(Consumer action) {
Objects.requireNonNull(action);
if (hasNext()) {
action.accept(next());
return true;
}
return false;
}
@Override
public final Spliterator trySplit() {
return null; // not splittable. Parallel streams would not gain any performance benefits yet. May be implemented in future
}
@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) {
/*Objects.requireNonNull(action);
while (hasNext()) {
action.accept(next());
}*/
while (tryAdvance(action)) {
}
}
final void close() {
try {
if (statement != null && !statement.isClosed()) {
statement.close(); // by JDBC spec: subsequently closes all result sets opened by this statement
}
} catch (SQLException e) {
throw new SQLRuntimeException(e);
}
}
}