hadoop TaskInputOutputContext 源码

  • 2022-10-20
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haddop TaskInputOutputContext 代码


 * 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,
 * See the License for the specific language governing permissions and
 * limitations under the License.

package org.apache.hadoop.mapreduce;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;

 * A context object that allows input and output from the task. It is only
 * supplied to the {@link Mapper} or {@link Reducer}.
 * @param <KEYIN> the input key type for the task
 * @param <VALUEIN> the input value type for the task
 * @param <KEYOUT> the output key type for the task
 * @param <VALUEOUT> the output value type for the task
public interface TaskInputOutputContext<KEYIN,VALUEIN,KEYOUT,VALUEOUT> 
       extends TaskAttemptContext {

   * Advance to the next key, value pair, returning null if at end.
   * @return the key object that was read into, or null if no more
  public boolean nextKeyValue() throws IOException, InterruptedException;
   * Get the current key.
   * @return the current key object or null if there isn't one
   * @throws IOException
   * @throws InterruptedException
  public KEYIN getCurrentKey() throws IOException, InterruptedException;

   * Get the current value.
   * @return the value object that was read into
   * @throws IOException
   * @throws InterruptedException
  public VALUEIN getCurrentValue() throws IOException, InterruptedException;

   * Generate an output key/value pair.
  public void write(KEYOUT key, VALUEOUT value) 
      throws IOException, InterruptedException;

   * Get the {@link OutputCommitter} for the task-attempt.
   * @return the <code>OutputCommitter</code> for the task-attempt
  public OutputCommitter getOutputCommitter();


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