/*
* Copyright © 2014 Cask Data, Inc.
*
* 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 co.cask.cdap.data2.dataset2.lib.table;
import co.cask.cdap.api.annotation.Beta;
import co.cask.cdap.api.common.Bytes;
import co.cask.cdap.api.data.batch.RecordScanner;
import co.cask.cdap.api.data.batch.Scannables;
import co.cask.cdap.api.data.batch.Split;
import co.cask.cdap.api.data.batch.SplitReader;
import co.cask.cdap.api.dataset.DataSetException;
import co.cask.cdap.api.dataset.lib.AbstractCloseableIterator;
import co.cask.cdap.api.dataset.lib.AbstractDataset;
import co.cask.cdap.api.dataset.lib.CloseableIterator;
import co.cask.cdap.api.dataset.lib.KeyValue;
import co.cask.cdap.api.dataset.lib.KeyValueTable;
import co.cask.cdap.api.dataset.lib.ObjectStore;
import co.cask.cdap.common.io.BinaryDecoder;
import co.cask.cdap.common.io.BinaryEncoder;
import co.cask.cdap.internal.io.ReflectionDatumReader;
import co.cask.cdap.internal.io.ReflectionDatumWriter;
import co.cask.cdap.internal.io.Schema;
import co.cask.cdap.internal.io.TypeRepresentation;
import com.google.common.base.Preconditions;
import com.google.common.reflect.TypeToken;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.lang.reflect.Type;
import java.util.List;
import javax.annotation.Nullable;
/**
* Default implementation for {@link ObjectStore}
* @param <T> the type of objects in the store
*/
@Beta
public class ObjectStoreDataset<T> extends AbstractDataset implements ObjectStore<T> {
private final KeyValueTable kvTable;
private final TypeRepresentation typeRep;
private final Schema schema;
private final ReflectionDatumWriter<T> datumWriter;
private final ReflectionDatumReader<T> datumReader;
public ObjectStoreDataset(String name, KeyValueTable kvTable, TypeRepresentation typeRep,
Schema schema, @Nullable ClassLoader classLoader) {
super(name, kvTable);
this.kvTable = kvTable;
this.typeRep = typeRep;
this.typeRep.setClassLoader(classLoader);
this.schema = schema;
this.datumWriter = new ReflectionDatumWriter<T>(this.schema);
this.datumReader = new ReflectionDatumReader<T>(this.schema, getTypeToken());
}
public ObjectStoreDataset(String name, KeyValueTable kvTable,
TypeRepresentation typeRep, Schema schema) {
this(name, kvTable, typeRep, schema, null);
}
@Override
public void write(String key, T object) {
kvTable.write(Bytes.toBytes(key), encode(object));
}
@Override
public void write(byte[] key, T object) {
kvTable.write(key, encode(object));
}
@Override
public T read(String key) {
return decode(kvTable.read(Bytes.toBytes(key)));
}
@Override
public CloseableIterator<KeyValue<byte[], T>> scan(byte[] startRow, byte[] stopRow) {
final CloseableIterator<KeyValue<byte[], byte[]>> keyValueIterator = kvTable.scan(startRow, stopRow);
return new AbstractCloseableIterator<KeyValue<byte[], T>>() {
boolean closed = false;
@Override
protected KeyValue<byte[], T> computeNext() {
Preconditions.checkState(!closed);
if (keyValueIterator.hasNext()) {
KeyValue<byte[], byte[]> row = keyValueIterator.next();
return new KeyValue<byte[], T>(row.getKey(), decode(row.getValue()));
}
close();
return null;
}
@Override
public void close() {
keyValueIterator.close();
endOfData();
closed = true;
}
};
}
@Override
public T read(byte[] key) {
byte[] read = kvTable.read(key);
return decode(read);
}
@Override
public void delete(byte[] key) {
kvTable.delete(key);
}
// this function only exists to reduce the scope of the SuppressWarnings annotation to a single cast.
@SuppressWarnings("unchecked")
private TypeToken<T> getTypeToken() {
return (TypeToken<T>) TypeToken.of(this.typeRep.toType());
}
private byte[] encode(T object) {
// encode T using schema
ByteArrayOutputStream bos = new ByteArrayOutputStream();
BinaryEncoder encoder = new BinaryEncoder(bos);
try {
this.datumWriter.encode(object, encoder);
} catch (IOException e) {
// SHOULD NEVER happen
throw new DataSetException("Failed to encode object to be written: " + e.getMessage(), e);
}
return bos.toByteArray();
}
private T decode(byte[] bytes) {
if (bytes == null) {
return null;
}
// decode T using schema
ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
BinaryDecoder decoder = new BinaryDecoder(bis);
try {
return this.datumReader.read(decoder, this.schema);
} catch (IOException e) {
// SHOULD NEVER happen
throw new DataSetException("Failed to decode read object: " + e.getMessage(), e);
}
}
// TODO: it should implement RecordScannable, but due to classloading issues it doesn't
// @Override
public RecordScanner<KeyValue<byte[], T>> createSplitRecordScanner(Split split) {
return Scannables.splitRecordScanner(createSplitReader(split), new ObjectRecordMaker());
}
// TODO: it should implement RecordScannable, but due to classloading issues it doesn't
// @Override
public Type getRecordType() {
return typeRep.toType();
}
@Override
public List<Split> getSplits() {
return kvTable.getSplits();
}
public List<Split> getSplits(int numSplits, byte[] start, byte[] stop) {
return kvTable.getSplits(numSplits, start, stop);
}
@Override
public SplitReader<byte[], T> createSplitReader(Split split) {
return new ObjectScanner(kvTable.createSplitReader(split));
}
/**
* {@link co.cask.cdap.api.data.batch.Scannables.RecordMaker} for {@link ObjectStoreDataset}.
*/
public class ObjectRecordMaker implements Scannables.RecordMaker<byte[], T, KeyValue<byte[], T>> {
@Override
public KeyValue<byte[], T> makeRecord(byte[] key, T value) {
return new KeyValue<byte[], T>(key, value);
}
}
/**
* The split reader for objects is reading a table split using the underlying KeyValueTable's split reader.
*/
public class ObjectScanner extends SplitReader<byte[], T> {
// the underlying KeyValueTable's split reader
private SplitReader<byte[], byte[]> reader;
public ObjectScanner(SplitReader<byte[], byte[]> reader) {
this.reader = reader;
}
@Override
public void initialize(Split split) throws InterruptedException {
this.reader.initialize(split);
}
@Override
public boolean nextKeyValue() throws InterruptedException {
return this.reader.nextKeyValue();
}
@Override
public byte[] getCurrentKey() throws InterruptedException {
return this.reader.getCurrentKey();
}
@Override
public T getCurrentValue() throws InterruptedException {
return decode(this.reader.getCurrentValue());
}
@Override
public void close() {
this.reader.close();
}
}
}