/* * 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.KeyValue; import org.apache.kafka.streams.StreamsConfig; import org.apache.kafka.streams.kstream.KStreamBuilder; import org.apache.kafka.streams.kstream.KStream; import org.apache.kafka.streams.kstream.KTable; import org.apache.kafka.streams.kstream.KeyValueMapper; import org.apache.kafka.streams.kstream.ValueMapper; import java.util.Arrays; import java.util.Locale; import java.util.Properties; /** * Demonstrates, using the high-level KStream DSL, how to implement the WordCount program * that computes a simple word occurrence histogram from an input text. * * In this example, the input stream reads from a topic named "streams-file-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. * * Before running this example you must create the input topic and the output topic (e.g. via * bin/kafka-topics.sh --create ...), and write some data to the input topic (e.g. via * bin/kafka-console-producer.sh). Otherwise you won't see any data arriving in the output topic. */ public class WordCountDemo { public static void main(String[] args) throws Exception { Properties props = new Properties(); props.put(StreamsConfig.APPLICATION_ID_CONFIG, "streams-wordcount"); props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092"); props.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName()); props.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName()); // 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.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest"); KStreamBuilder builder = new KStreamBuilder(); KStream<String, String> source = builder.stream("streams-file-input"); KTable<String, Long> counts = source .flatMapValues(new ValueMapper<String, Iterable<String>>() { @Override public Iterable<String> apply(String value) { return Arrays.asList(value.toLowerCase(Locale.getDefault()).split(" ")); } }).map(new KeyValueMapper<String, String, KeyValue<String, String>>() { @Override public KeyValue<String, String> apply(String key, String value) { return new KeyValue<>(value, value); } }) .groupByKey() .count("Counts"); // need to override value serde to Long type counts.to(Serdes.String(), Serdes.Long(), "streams-wordcount-output"); KafkaStreams streams = new KafkaStreams(builder, props); streams.start(); // usually the stream application would be running forever, // in this example we just let it run for some time and stop since the input data is finite. Thread.sleep(5000L); streams.close(); } }