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/*
* 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.spark.examples.sql.streaming;
import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Encoders;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.SparkSession;
import org.apache.spark.sql.streaming.StreamingQuery;
import java.util.Arrays;
import java.util.Iterator;
/**
* Consumes messages from one or more topics in Kafka and does wordcount.
* Usage: JavaStructuredKafkaWordCount <bootstrap-servers> <subscribe-type> <topics>
* <bootstrap-servers> The Kafka "bootstrap.servers" configuration. A
* comma-separated list of host:port.
* <subscribe-type> There are three kinds of type, i.e. 'assign', 'subscribe',
* 'subscribePattern'.
* |- <assign> Specific TopicPartitions to consume. Json string
* | {"topicA":[0,1],"topicB":[2,4]}.
* |- <subscribe> The topic list to subscribe. A comma-separated list of
* | topics.
* |- <subscribePattern> The pattern used to subscribe to topic(s).
* | Java regex string.
* |- Only one of "assign, "subscribe" or "subscribePattern" options can be
* | specified for Kafka source.
* <topics> Different value format depends on the value of 'subscribe-type'.
*
* Example:
* `$ bin/run-example \
* sql.streaming.JavaStructuredKafkaWordCount host1:port1,host2:port2 \
* subscribe topic1,topic2`
*/
public final class JavaStructuredKafkaWordCount {
public static void main(String[] args) throws Exception {
if (args.length < 3) {
System.err.println("Usage: JavaStructuredKafkaWordCount <bootstrap-servers> " +
"<subscribe-type> <topics>");
System.exit(1);
}
String bootstrapServers = args[0];
String subscribeType = args[1];
String topics = args[2];
SparkSession spark = SparkSession
.builder()
.appName("JavaStructuredKafkaWordCount")
.getOrCreate();
// Create DataSet representing the stream of input lines from kafka
Dataset<String> lines = spark
.readStream()
.format("kafka")
.option("kafka.bootstrap.servers", bootstrapServers)
.option(subscribeType, topics)
.load()
.selectExpr("CAST(value AS STRING)")
.as(Encoders.STRING());
// Generate running word count
Dataset<Row> wordCounts = lines.flatMap(new FlatMapFunction<String, String>() {
@Override
public Iterator<String> call(String x) {
return Arrays.asList(x.split(" ")).iterator();
}
}, Encoders.STRING()).groupBy("value").count();
// Start running the query that prints the running counts to the console
StreamingQuery query = wordCounts.writeStream()
.outputMode("complete")
.format("console")
.start();
query.awaitTermination();
}
}
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