inputSplit.java分析

/**
* 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;

import java.io.IOException;

import org.apache.hadoop.mapreduce.InputFormat;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.RecordReader;

/**
* <code>InputSplit</code> represents the data to be processed by an
* individual {@link Mapper}.
*代表将要被mapper独自处理的分割文件。
* <p>Typically, it presents a byte-oriented view on the input and is the
* responsibility of {@link RecordReader} of the job to process this and present
* a record-oriented view.
*
* @see InputFormat
* @see RecordReader
*/
public abstract class InputSplit {
/**
* Get the size of the split, so that the input splits can be sorted by size.
* 得到分割文件的大小 这样分割文件可以按大小排序
* @return the number of bytes in the split
* @throws IOException
* @throws InterruptedException
*/
public abstract long getLength() throws IOException, InterruptedException;

/**
* Get the list of nodes by name where the data for the split would be local.
* The locations do not need to be serialized.
* 获得 分割文件将要本地化哪里的节点列表 ，本地化不需要序列化。
* @return a new array of the node nodes.
* @throws IOException
* @throws InterruptedException
*/
public abstract
String[] getLocations() throws IOException, InterruptedException;
}