examples/spark/src/main/java/org/apache/nemo/examples/spark/JavaWordCount.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.nemo.examples.spark;

import org.apache.nemo.compiler.frontend.spark.core.rdd.SparkJavaPairRDD;
import org.apache.nemo.compiler.frontend.spark.core.rdd.SparkJavaRDD;
import org.apache.nemo.compiler.frontend.spark.sql.SparkSession;
import scala.Tuple2;

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;

/**
 * Java Wordcount example.
 */
public final class JavaWordCount {
  private static final Pattern SPACE = Pattern.compile(" ");

  /**
   * Private constructor.
   */
  private JavaWordCount() {
  }

  /**
   * Main method.
   *
   * @param args arguments.
   * @throws Exception exceptions.
   */
  public static void main(final String[] args) throws Exception {

    if (args.length < 1) {
      System.err.println("Usage: JavaWordCount <input_file> [<output_file>]");
      System.exit(1);
    }

    SparkSession spark = SparkSession
      .builder()
      .appName("JavaWordCount")
      .getOrCreate();

    SparkJavaRDD<String> lines = spark.read().textFile(args[0]).javaRDD();

    SparkJavaRDD<String> words = lines.flatMap(s -> Arrays.asList(SPACE.split(s)).iterator());

    SparkJavaPairRDD<String, Integer> ones = words.mapToPair(s -> new Tuple2<>(s, 1));

    SparkJavaPairRDD<String, Integer> counts = ones.reduceByKey((i1, i2) -> i1 + i2);

    List<Tuple2<String, Integer>> output = counts.collect();

    final boolean writemode = args[1] != null;
    if (writemode) { // print to output file
      try (BufferedWriter bw = new BufferedWriter(new FileWriter(args[1]))) {
        for (Tuple2<?, ?> tuple : output) {
          bw.write(tuple._1 + ": " + tuple._2 + "\n");
        }
      } catch (IOException e) {
        throw new RuntimeException(e);
      }
    } else { // print to console.
      for (Tuple2<?, ?> tuple : output) {
        System.out.println(tuple._1 + ": " + tuple._2);
      }
    }
    spark.stop();
  }
}