001 /** 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018 package org.apache.hadoop.mapreduce.lib.input; 019 020 import java.io.IOException; 021 022 import org.apache.hadoop.classification.InterfaceAudience; 023 import org.apache.hadoop.classification.InterfaceStability; 024 import org.apache.hadoop.conf.Configuration; 025 import org.apache.hadoop.fs.Path; 026 import org.apache.hadoop.io.BytesWritable; 027 import org.apache.hadoop.io.LongWritable; 028 import org.apache.hadoop.io.compress.CompressionCodec; 029 import org.apache.hadoop.io.compress.CompressionCodecFactory; 030 import org.apache.hadoop.mapreduce.InputSplit; 031 import org.apache.hadoop.mapreduce.JobContext; 032 import org.apache.hadoop.mapreduce.RecordReader; 033 import org.apache.hadoop.mapreduce.TaskAttemptContext; 034 035 /** 036 * FixedLengthInputFormat is an input format used to read input files 037 * which contain fixed length records. The content of a record need not be 038 * text. It can be arbitrary binary data. Users must configure the record 039 * length property by calling: 040 * FixedLengthInputFormat.setRecordLength(conf, recordLength);<br><br> or 041 * conf.setInt(FixedLengthInputFormat.FIXED_RECORD_LENGTH, recordLength); 042 * <br><br> 043 * @see FixedLengthRecordReader 044 */ 045 @InterfaceAudience.Public 046 @InterfaceStability.Stable 047 public class FixedLengthInputFormat 048 extends FileInputFormat<LongWritable, BytesWritable> { 049 050 public static final String FIXED_RECORD_LENGTH = 051 "fixedlengthinputformat.record.length"; 052 053 /** 054 * Set the length of each record 055 * @param conf configuration 056 * @param recordLength the length of a record 057 */ 058 public static void setRecordLength(Configuration conf, int recordLength) { 059 conf.setInt(FIXED_RECORD_LENGTH, recordLength); 060 } 061 062 /** 063 * Get record length value 064 * @param conf configuration 065 * @return the record length, zero means none was set 066 */ 067 public static int getRecordLength(Configuration conf) { 068 return conf.getInt(FIXED_RECORD_LENGTH, 0); 069 } 070 071 @Override 072 public RecordReader<LongWritable, BytesWritable> 073 createRecordReader(InputSplit split, TaskAttemptContext context) 074 throws IOException, InterruptedException { 075 int recordLength = getRecordLength(context.getConfiguration()); 076 if (recordLength <= 0) { 077 throw new IOException("Fixed record length " + recordLength 078 + " is invalid. It should be set to a value greater than zero"); 079 } 080 return new FixedLengthRecordReader(recordLength); 081 } 082 083 @Override 084 protected boolean isSplitable(JobContext context, Path file) { 085 final CompressionCodec codec = 086 new CompressionCodecFactory(context.getConfiguration()).getCodec(file); 087 return (null == codec); 088 } 089 090 }