Java Sample Code

Function Description

In Spark applications, use Structured Streaming to call Kafka APIs to obtain word records. Classify word records to obtain the number of records of each word.

Sample Code

The following code snippets are used as an example. For complete codes, see com.huawei.bigdata.spark.examples.SecurityKafkaWordCount.

• For a normal cluster, comment out .option("kafka.security.protocol", protocol) in the 61st line of the com.huawei.bigdata.spark.examples.SecurityKafkaWordCount class in the sample code.

• When new data is available in Streaming DataFrame/Dataset, outputMode is used for configuring data written to the Streaming receiver. The default value is append.

public class SecurityKafkaWordCount
{
  public static void main(String[] args) throws Exception {
    if (args.length < 6) {
      System.err.println("Usage: SecurityKafkaWordCount <bootstrap-servers> " +
        "<subscribe-type> <topics> <protocol> <service> <domain>");
      System.exit(1);
    }

    String bootstrapServers = args[0];
    String subscribeType = args[1];
    String topics = args[2];
    String protocol = args[3];
    String service = args[4];
    String domain = args[5];

    SparkSession spark = SparkSession
      .builder()
      .appName("SecurityKafkaWordCount")
      .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)
      .option("kafka.security.protocol", protocol)
      .option("kafka.sasl.kerberos.service.name", service)
      .option("kafka.kerberos.domain.name", domain)
      .load()
      .selectExpr("CAST(value AS STRING)")
      .as(Encoders.STRING());

    // Generate the running word counts.
    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();
  }
}