hadoop UserDefinedValueAggregatorDescriptor 源码
haddop UserDefinedValueAggregatorDescriptor 代码
文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/lib/aggregate/UserDefinedValueAggregatorDescriptor.java
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.mapred.lib.aggregate;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.mapred.JobConf;
/**
* This class implements a wrapper for a user defined value aggregator
* descriptor.
* It serves two functions: One is to create an object of
* ValueAggregatorDescriptor from the name of a user defined class that may be
* dynamically loaded. The other is to delegate invocations of
* generateKeyValPairs function to the created object.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class UserDefinedValueAggregatorDescriptor extends org.apache.hadoop.
mapreduce.lib.aggregate.UserDefinedValueAggregatorDescriptor
implements ValueAggregatorDescriptor {
/**
* Create an instance of the given class
* @param className the name of the class
* @return a dynamically created instance of the given class
*/
public static Object createInstance(String className) {
return org.apache.hadoop.mapreduce.lib.aggregate.
UserDefinedValueAggregatorDescriptor.createInstance(className);
}
/**
*
* @param className the class name of the user defined descriptor class
* @param job a configure object used for decriptor configuration
*/
public UserDefinedValueAggregatorDescriptor(String className, JobConf job) {
super(className, job);
((ValueAggregatorDescriptor)theAggregatorDescriptor).configure(job);
}
/**
* Do nothing.
*/
public void configure(JobConf job) {
}
}
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