content: /*
   * 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.kafka.streams.examples.wordcount;
  
  import org.apache.kafka.clients.consumer.ConsumerConfig;
  import org.apache.kafka.common.serialization.Serdes;
  import org.apache.kafka.streams.KafkaStreams;
  import org.apache.kafka.streams.StreamsBuilder;
  import org.apache.kafka.streams.StreamsConfig;
  import org.apache.kafka.streams.kstream.KStream;
  import org.apache.kafka.streams.kstream.KTable;
  import org.apache.kafka.streams.kstream.Produced;
  
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.util.Arrays;
  import java.util.Locale;
  import java.util.Properties;
  import java.util.concurrent.CountDownLatch;
  
  /**
   * Demonstrates, using the high-level KStream DSL, how to implement the WordCount program
   * that computes a simple word occurrence histogram from an input text.
   * <p>
   * In this example, the input stream reads from a topic named "streams-plaintext-input", where the values of messages
   * represent lines of text; and the histogram output is written to topic "streams-wordcount-output" where each record
   * is an updated count of a single word.
   * <p>
   * Before running this example you must create the input topic and the output topic (e.g. via
   * {@code bin/kafka-topics.sh --create ...}), and write some data to the input topic (e.g. via
   * {@code bin/kafka-console-producer.sh}). Otherwise you won't see any data arriving in the output topic.
   */
  public final class WordCountDemo {
  
      public static final String INPUT_TOPIC = "streams-plaintext-input";
      public static final String OUTPUT_TOPIC = "streams-wordcount-output";
  
      static Properties streamsConfig(final String[] args) throws IOException {
          final Properties props = new Properties();
          if (args != null && args.length > 0) {
              try (final FileInputStream fis = new FileInputStream(args[0])) {
                  props.load(fis);
              }
              if (args.length > 1) {
                  System.out.println("Warning: Some command line arguments were ignored. This demo only accepts an optional configuration file.");
              }
          }
          props.putIfAbsent(StreamsConfig.APPLICATION_ID_CONFIG, "streams-wordcount");
          props.putIfAbsent(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
          props.putIfAbsent(StreamsConfig.STATESTORE_CACHE_MAX_BYTES_CONFIG, 0);
          props.putIfAbsent(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.StringSerde.class);
          props.putIfAbsent(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.StringSerde.class);
  
          // setting offset reset to earliest so that we can re-run the demo code with the same pre-loaded data
          // Note: To re-run the demo, you need to use the offset reset tool:
          // https://cwiki.apache.org/confluence/display/KAFKA/Kafka+Streams+Application+Reset+Tool
          props.putIfAbsent(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
          return props;
      }
  
      static void createWordCountStream(final StreamsBuilder builder) {
          final KStream<String, String> source = builder.stream(INPUT_TOPIC);
  
          final KTable<String, Long> counts = source
              .flatMapValues(value -> Arrays.asList(value.toLowerCase(Locale.getDefault()).split("\\W+")))
              .groupBy((key, value) -> value)
              .count();
  
          // need to override value serde to Long type
          counts.toStream().to(OUTPUT_TOPIC, Produced.with(Serdes.String(), Serdes.Long()));
      }
  
      public static void main(final String[] args) throws IOException {
          final Properties props = streamsConfig(args);
  
          final StreamsBuilder builder = new StreamsBuilder();
          createWordCountStream(builder);
          final KafkaStreams streams = new KafkaStreams(builder.build(), props);
          final CountDownLatch latch = new CountDownLatch(1);
  
          // attach shutdown handler to catch control-c
          Runtime.getRuntime().addShutdownHook(new Thread("streams-wordcount-shutdown-hook") {
              @Override
              public void run() {
                  streams.close();
                  latch.countDown();
              }
          });
  
          try {
              streams.start();
              latch.await();
          } catch (final Throwable e) {
              System.exit(1);
          }
          System.exit(0);
      }
  }
  