DelegatingMapper.java
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上传日期:2018-01-08
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- /**
- * 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.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)
- */
- 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();
- }
- }
- }