org.apache.flink.api.common.accumulators.ListAccumulator.java Source code

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Here is the source code for org.apache.flink.api.common.accumulators.ListAccumulator.java

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/*
 * 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 java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;

import org.apache.commons.lang3.SerializationUtils;

/**
 * * This accumulator stores a collection of objects which are immediately serialized to cope with object reuse.
 * * When the objects are requested again, they are deserialized.
 * @param <T> The type of the accumulated objects
 */
public class ListAccumulator<T> implements Accumulator<T, ArrayList<T>> {

    private static final long serialVersionUID = 1L;

    private ArrayList<byte[]> localValue = new ArrayList<byte[]>();

    @Override
    public void add(T value) {
        byte[] byteArray = SerializationUtils.serialize((Serializable) value);
        localValue.add(byteArray);
    }

    @Override
    public ArrayList<T> getLocalValue() {
        ArrayList<T> arrList = new ArrayList<T>();
        for (byte[] byteArr : localValue) {
            T item = SerializationUtils.deserialize(byteArr);
            arrList.add(item);
        }
        return arrList;
    }

    @Override
    public void resetLocal() {
        localValue.clear();
    }

    @Override
    public void merge(Accumulator<T, ArrayList<T>> other) {
        localValue.addAll(((ListAccumulator<T>) other).localValue);
    }

    @Override
    public Accumulator<T, ArrayList<T>> clone() {
        ListAccumulator<T> newInstance = new ListAccumulator<T>();
        for (byte[] item : localValue) {
            newInstance.localValue.add(item.clone());
        }
        return newInstance;
    }

    @Override
    public void write(ObjectOutputStream out) throws IOException {
        int numItems = localValue.size();
        out.writeInt(numItems);
        for (byte[] item : localValue) {
            out.writeInt(item.length);
            out.write(item);
        }
    }

    @Override
    public void read(ObjectInputStream in) throws IOException {
        int numItems = in.readInt();
        for (int i = 0; i < numItems; i++) {
            int len = in.readInt();
            byte[] obj = new byte[len];
            in.read(obj);
            localValue.add(obj);
        }
    }

}