co.cask.cdap.internal.app.runtime.batch.dataset.input.DelegatingRecordReader.java Source code

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/*
 * Copyright  2016 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.internal.app.runtime.batch.dataset.input;

import org.apache.hadoop.mapreduce.InputFormat;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.util.ReflectionUtils;

import java.io.IOException;

/**
 * This is a delegating RecordReader, which delegates the functionality to the
 * underlying record reader in {@link TaggedInputSplit}
 *
 * @param <K> Type of key
 * @param <V> Type of value
 */
public class DelegatingRecordReader<K, V> extends RecordReader<K, V> {
    private final RecordReader<K, V> originalRR;

    /**
     * Constructs the DelegatingRecordReader.
     *
     * @param taggedInputSplit TaggedInputSplit object
     * @param context TaskAttemptContext object
     *
     * @throws IOException
     * @throws InterruptedException
     */
    @SuppressWarnings("unchecked")
    public DelegatingRecordReader(TaggedInputSplit taggedInputSplit, TaskAttemptContext context)
            throws IOException, InterruptedException {
        // Find the InputFormat and then the RecordReader from the TaggedInputSplit.
        InputFormat<K, V> inputFormat = (InputFormat<K, V>) ReflectionUtils
                .newInstance(taggedInputSplit.getInputFormatClass(), context.getConfiguration());
        InputSplit inputSplit = taggedInputSplit.getInputSplit();
        originalRR = inputFormat.createRecordReader(inputSplit, context);
    }

    @Override
    public void close() throws IOException {
        originalRR.close();
    }

    @Override
    public K getCurrentKey() throws IOException, InterruptedException {
        return originalRR.getCurrentKey();
    }

    @Override
    public V getCurrentValue() throws IOException, InterruptedException {
        return originalRR.getCurrentValue();
    }

    @Override
    public float getProgress() throws IOException, InterruptedException {
        return originalRR.getProgress();
    }

    @Override
    public void initialize(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
        InputSplit inputSplit = ((TaggedInputSplit) split).getInputSplit();
        originalRR.initialize(inputSplit, context);
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        return originalRR.nextKeyValue();
    }

}