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    
019    package org.apache.hadoop.mapred.lib;
020    
021    import java.io.IOException;
022    import java.util.StringTokenizer;
023    
024    import org.apache.hadoop.classification.InterfaceAudience;
025    import org.apache.hadoop.classification.InterfaceStability;
026    import org.apache.hadoop.io.LongWritable;
027    import org.apache.hadoop.io.Text;
028    import org.apache.hadoop.mapred.MapReduceBase;
029    import org.apache.hadoop.mapred.Mapper;
030    import org.apache.hadoop.mapred.OutputCollector;
031    import org.apache.hadoop.mapred.Reporter;
032    
033    
034    /** 
035     * A {@link Mapper} that maps text values into <token,freq> pairs.  Uses
036     * {@link StringTokenizer} to break text into tokens. 
037     */
038    @InterfaceAudience.Public
039    @InterfaceStability.Stable
040    public class TokenCountMapper<K> extends MapReduceBase
041        implements Mapper<K, Text, Text, LongWritable> {
042    
043      public void map(K key, Text value,
044                      OutputCollector<Text, LongWritable> output,
045                      Reporter reporter)
046        throws IOException {
047        // get input text
048        String text = value.toString();       // value is line of text
049    
050        // tokenize the value
051        StringTokenizer st = new StringTokenizer(text);
052        while (st.hasMoreTokens()) {
053          // output <token,1> pairs
054          output.collect(new Text(st.nextToken()), new LongWritable(1));
055        }  
056      }
057      
058    }