/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.flink.api.common.accumulators;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.core.memory.DataInputViewStreamWrapper;
import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
/**
* This accumulator stores a collection of objects in serialized form, so that the stored objects
* are not affected by modifications to the original objects.
*
* Objects may be deserialized on demand with a specific classloader.
*
* @param <T> The type of the accumulated objects
*/
@PublicEvolving
public class SerializedListAccumulator<T> implements Accumulator<T, ArrayList<byte[]>> {
private static final long serialVersionUID = 1L;
private ArrayList<byte[]> localValue = new ArrayList<>();
@Override
public void add(T value) {
throw new UnsupportedOperationException();
}
public void add(T value, TypeSerializer<T> serializer) throws IOException {
try {
ByteArrayOutputStream outStream = new ByteArrayOutputStream();
DataOutputViewStreamWrapper out = new DataOutputViewStreamWrapper(outStream);
serializer.serialize(value, out);
localValue.add(outStream.toByteArray());
}
catch (IOException e) {
throw new IOException("Failed to serialize value '" + value + '\'', e);
}
}
@Override
public ArrayList<byte[]> getLocalValue() {
return localValue;
}
@Override
public void resetLocal() {
localValue.clear();
}
@Override
public void merge(Accumulator<T, ArrayList<byte[]>> other) {
localValue.addAll(other.getLocalValue());
}
@Override
public SerializedListAccumulator<T> clone() {
SerializedListAccumulator<T> newInstance = new SerializedListAccumulator<T>();
newInstance.localValue = new ArrayList<byte[]>(localValue);
return newInstance;
}
@SuppressWarnings("unchecked")
public static <T> List<T> deserializeList(ArrayList<byte[]> data, TypeSerializer<T> serializer)
throws IOException, ClassNotFoundException
{
List<T> result = new ArrayList<T>(data.size());
for (byte[] bytes : data) {
ByteArrayInputStream inStream = new ByteArrayInputStream(bytes);
DataInputViewStreamWrapper in = new DataInputViewStreamWrapper(inStream);
T val = serializer.deserialize(in);
result.add(val);
}
return result;
}
@Override
public String toString() {
return "SerializedListAccumulator: " + localValue.size() + " elements";
}
}