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
019package org.apache.hadoop.mapreduce.lib.aggregate;
020
021import java.io.IOException;
022import java.util.Iterator;
023import java.util.Map.Entry;
024
025import org.apache.hadoop.classification.InterfaceAudience;
026import org.apache.hadoop.classification.InterfaceStability;
027import org.apache.hadoop.io.Text;
028import org.apache.hadoop.io.Writable;
029import org.apache.hadoop.io.WritableComparable;
030import org.apache.hadoop.mapreduce.Mapper;
031
032/**
033 * This class implements the generic mapper of Aggregate.
034 */
035@InterfaceAudience.Public
036@InterfaceStability.Stable
037public class ValueAggregatorMapper<K1 extends WritableComparable<?>,
038                                   V1 extends Writable>
039  extends Mapper<K1, V1, Text, Text> {
040
041  public void setup(Context context) 
042      throws IOException, InterruptedException {
043    ValueAggregatorJobBase.setup(context.getConfiguration());
044  }
045  
046  /**
047   *  the map function. It iterates through the value aggregator descriptor 
048   *  list to generate aggregation id/value pairs and emit them.
049   */
050  public void map(K1 key, V1 value,
051      Context context) throws IOException, InterruptedException  {
052
053    Iterator<?> iter = 
054      ValueAggregatorJobBase.aggregatorDescriptorList.iterator();
055    while (iter.hasNext()) {
056      ValueAggregatorDescriptor ad = (ValueAggregatorDescriptor) iter.next();
057      Iterator<Entry<Text, Text>> ens =
058        ad.generateKeyValPairs(key, value).iterator();
059      while (ens.hasNext()) {
060        Entry<Text, Text> en = ens.next();
061        context.write(en.getKey(), en.getValue());
062      }
063    }
064  }
065}