co.cask.cdap.data2.dataset2.lib.partitioned.EmptyInputFormat.java Source code

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/*
 * Copyright  2015 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.partitioned;

import org.apache.hadoop.mapreduce.InputFormat;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;

import java.io.IOException;
import java.util.Collections;
import java.util.List;

/**
 * An InputFormat that returns no data.
 * @param <K> the key class
 * @param <V> the value class
 */
public class EmptyInputFormat<K, V> extends InputFormat<K, V> {

    @Override
    public List<InputSplit> getSplits(JobContext context) throws IOException, InterruptedException {
        return Collections.emptyList();
    }

    @Override
    public RecordReader<K, V> createRecordReader(InputSplit split, TaskAttemptContext context) {
        return new RecordReader<K, V>() {
            @Override
            public void initialize(InputSplit split, TaskAttemptContext context) {
                // do nothing
            }

            @Override
            public boolean nextKeyValue() {
                return false;
            }

            @Override
            public K getCurrentKey() {
                return null;
            }

            @Override
            public V getCurrentValue() {
                return null;
            }

            @Override
            public float getProgress() {
                return 1.0F;
            }

            @Override
            public void close() {
                // nothing to do
            }
        };
    }
}