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WordCount.java
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WordCount.java
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/*
* Copyright (C) 2016 Google Inc.
*
* Licensed 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 com.google.cloud.teleport.templates;
import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.io.TextIO;
import org.apache.beam.sdk.metrics.Counter;
import org.apache.beam.sdk.metrics.Metrics;
import org.apache.beam.sdk.options.Description;
import org.apache.beam.sdk.options.PipelineOptions;
import org.apache.beam.sdk.options.PipelineOptionsFactory;
import org.apache.beam.sdk.options.ValueProvider;
import org.apache.beam.sdk.transforms.Count;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.MapElements;
import org.apache.beam.sdk.transforms.PTransform;
import org.apache.beam.sdk.transforms.ParDo;
import org.apache.beam.sdk.transforms.SimpleFunction;
import org.apache.beam.sdk.values.KV;
import org.apache.beam.sdk.values.PCollection;
/**
* An template that counts words in Shakespeare.
*/
public class WordCount {
static class ExtractWordsFn extends DoFn<String, String> {
private final Counter emptyLines = Metrics.counter(ExtractWordsFn.class, "emptyLines");
@ProcessElement
public void processElement(ProcessContext c) {
if (c.element().trim().isEmpty()) {
emptyLines.inc();
}
// Split the line into words.
String[] words = c.element().split("[^a-zA-Z']+");
// Output each word encountered into the output PCollection.
for (String word : words) {
if (!word.isEmpty()) {
c.output(word);
}
}
}
}
/** A SimpleFunction that converts a Word and Count into a printable string. */
public static class FormatAsTextFn extends SimpleFunction<KV<String, Long>, String> {
@Override
public String apply(KV<String, Long> input) {
return input.getKey() + ": " + input.getValue();
}
}
/**
* A PTransform that converts a PCollection containing lines of text into a PCollection of
* formatted word counts.
*/
public static class CountWords extends PTransform<PCollection<String>,
PCollection<KV<String, Long>>> {
@Override
public PCollection<KV<String, Long>> expand(PCollection<String> lines) {
// Convert lines of text into individual words.
PCollection<String> words = lines.apply(
ParDo.of(new ExtractWordsFn()));
// Count the number of times each word occurs.
PCollection<KV<String, Long>> wordCounts =
words.apply(Count.<String>perElement());
return wordCounts;
}
}
/**
* Options supported by {@link com.google.cloud.teleport.templates.WordCount}.
*
* <p>Inherits standard configuration options.
*/
public interface WordCountOptions extends PipelineOptions {
@Description("Path of the file to read from")
ValueProvider<String> getInputFile();
void setInputFile(ValueProvider<String> value);
@Description("Path of the file to write to")
ValueProvider<String> getOutput();
void setOutput(ValueProvider<String> value);
}
public static void main(String[] args) {
WordCountOptions options = PipelineOptionsFactory.fromArgs(args).withValidation()
.as(WordCountOptions.class);
Pipeline p = Pipeline.create(options);
p.apply("ReadLines", TextIO.read().from(options.getInputFile()))
.apply(new CountWords())
.apply(MapElements.via(new FormatAsTextFn()))
.apply("WriteCounts", TextIO.write().to(options.getOutput()));
p.run();
}
}