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 }