hadoop SequenceFileAsTextRecordReader 源码

haddop SequenceFileAsTextRecordReader 代码

文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/lib/input/SequenceFileAsTextRecordReader.java

/**
 * 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.hadoop.mapreduce.lib.input;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;

/**
 * This class converts the input keys and values to their String forms by
 * calling toString() method. This class to SequenceFileAsTextInputFormat
 * class is as LineRecordReader class to TextInputFormat class.
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class SequenceFileAsTextRecordReader
  extends RecordReader<Text, Text> {
  
  private final SequenceFileRecordReader<WritableComparable<?>, Writable>
    sequenceFileRecordReader;

  private Text key;
  private Text value;

  public SequenceFileAsTextRecordReader()
    throws IOException {
    sequenceFileRecordReader =
      new SequenceFileRecordReader<WritableComparable<?>, Writable>();
  }

  public void initialize(InputSplit split, TaskAttemptContext context)
      throws IOException, InterruptedException {
    sequenceFileRecordReader.initialize(split, context);
  }

  @Override
  public Text getCurrentKey() 
      throws IOException, InterruptedException {
    return key;
  }
  
  @Override
  public Text getCurrentValue() 
      throws IOException, InterruptedException {
    return value;
  }
  
  /** Read key/value pair in a line. */
  public synchronized boolean nextKeyValue() 
      throws IOException, InterruptedException {
    if (!sequenceFileRecordReader.nextKeyValue()) {
      return false;
    }
    if (key == null) {
      key = new Text(); 
    }
    if (value == null) {
      value = new Text(); 
    }
    key.set(sequenceFileRecordReader.getCurrentKey().toString());
    value.set(sequenceFileRecordReader.getCurrentValue().toString());
    return true;
  }
  
  public float getProgress() throws IOException,  InterruptedException {
    return sequenceFileRecordReader.getProgress();
  }
  
  public synchronized void close() throws IOException {
    sequenceFileRecordReader.close();
  }
}

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