hadoop DelegatingMapper 源码
haddop DelegatingMapper 代码
文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/lib/DelegatingMapper.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;
import java.io.IOException;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.util.ReflectionUtils;
/**
* An {@link Mapper} that delegates behaviour of paths to multiple other
* mappers.
*
* @see MultipleInputs#addInputPath(JobConf, Path, Class, Class)
*/
@InterfaceAudience.Private
@InterfaceStability.Unstable
public class DelegatingMapper<K1, V1, K2, V2> implements Mapper<K1, V1, K2, V2> {
private JobConf conf;
private Mapper<K1, V1, K2, V2> mapper;
@SuppressWarnings("unchecked")
public void map(K1 key, V1 value, OutputCollector<K2, V2> outputCollector,
Reporter reporter) throws IOException {
if (mapper == null) {
// Find the Mapper from the TaggedInputSplit.
TaggedInputSplit inputSplit = (TaggedInputSplit) reporter.getInputSplit();
mapper = (Mapper<K1, V1, K2, V2>) ReflectionUtils.newInstance(inputSplit
.getMapperClass(), conf);
}
mapper.map(key, value, outputCollector, reporter);
}
public void configure(JobConf conf) {
this.conf = conf;
}
public void close() throws IOException {
if (mapper != null) {
mapper.close();
}
}
}
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