/**
* 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.crunch.examples;
import java.io.Serializable;
import org.apache.crunch.DoFn;
import org.apache.crunch.Emitter;
import org.apache.crunch.PCollection;
import org.apache.crunch.PTable;
import org.apache.crunch.Pipeline;
import org.apache.crunch.PipelineResult;
import org.apache.crunch.impl.mr.MRPipeline;
import org.apache.crunch.types.writable.Writables;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.util.GenericOptionsParser;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
public class WordCount extends Configured implements Tool, Serializable {
public int run(String[] args) throws Exception {
if (args.length != 2) {
System.err.println();
System.err.println("Usage: " + this.getClass().getName() + " [generic options] input output");
System.err.println();
GenericOptionsParser.printGenericCommandUsage(System.err);
return 1;
}
// Create an object to coordinate pipeline creation and execution.
Pipeline pipeline = new MRPipeline(WordCount.class, getConf());
// Reference a given text file as a collection of Strings.
PCollection<String> lines = pipeline.readTextFile(args[0]);
// Define a function that splits each line in a PCollection of Strings into
// a
// PCollection made up of the individual words in the file.
PCollection<String> words = lines.parallelDo(new DoFn<String, String>() {
public void process(String line, Emitter<String> emitter) {
for (String word : line.split("\\s+")) {
emitter.emit(word);
}
}
}, Writables.strings()); // Indicates the serialization format
// The count method applies a series of Crunch primitives and returns
// a map of the unique words in the input PCollection to their counts.
// Best of all, the count() function doesn't need to know anything about
// the kind of data stored in the input PCollection.
PTable<String, Long> counts = words.count();
// Instruct the pipeline to write the resulting counts to a text file.
pipeline.writeTextFile(counts, args[1]);
// Execute the pipeline as a MapReduce.
PipelineResult result = pipeline.done();
return result.succeeded() ? 0 : 1;
}
public static void main(String[] args) throws Exception {
int result = ToolRunner.run(new Configuration(), new WordCount(), args);
System.exit(result);
}
}