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.aggregate; 020 021 import org.apache.hadoop.classification.InterfaceAudience; 022 import org.apache.hadoop.classification.InterfaceStability; 023 import org.apache.hadoop.mapred.JobConf; 024 025 /** 026 * This class implements a wrapper for a user defined value aggregator 027 * descriptor. 028 * It serves two functions: One is to create an object of 029 * ValueAggregatorDescriptor from the name of a user defined class that may be 030 * dynamically loaded. The other is to delegate invocations of 031 * generateKeyValPairs function to the created object. 032 */ 033 @InterfaceAudience.Public 034 @InterfaceStability.Stable 035 public class UserDefinedValueAggregatorDescriptor extends org.apache.hadoop. 036 mapreduce.lib.aggregate.UserDefinedValueAggregatorDescriptor 037 implements ValueAggregatorDescriptor { 038 039 /** 040 * Create an instance of the given class 041 * @param className the name of the class 042 * @return a dynamically created instance of the given class 043 */ 044 public static Object createInstance(String className) { 045 return org.apache.hadoop.mapreduce.lib.aggregate. 046 UserDefinedValueAggregatorDescriptor.createInstance(className); 047 } 048 049 /** 050 * 051 * @param className the class name of the user defined descriptor class 052 * @param job a configure object used for decriptor configuration 053 */ 054 public UserDefinedValueAggregatorDescriptor(String className, JobConf job) { 055 super(className, job); 056 ((ValueAggregatorDescriptor)theAggregatorDescriptor).configure(job); 057 } 058 059 /** 060 * Do nothing. 061 */ 062 public void configure(JobConf job) { 063 064 } 065 066 }