Spark 2.4.0 Avro Java - cannot resolve method from_avro

Question

I'm trying to run a spark stream from a kafka queue containing Avro messages.

As per https://spark.apache.org/docs/latest/sql-data-sources-avro.html I should be able to use from_avro to convert column value to Dataset<Row>.

However, I'm unable to compile the project as it complains from_avro cannot be found. I can see the method declared in package.class of the dependency.

How can I use the from_avro method from org.apache.spark.sql.avro in my Java code locally?

import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.SparkSession;

import static org.apache.spark.sql.functions.*;
import org.apache.spark.sql.avro.*;


public class AvroStreamTest {
    public static void main(String[] args) throws IOException, InterruptedException {

     // Creating local sparkSession here...

        Dataset<Row> df = sparkSession
                .readStream()
                .format("kafka")
                .option("kafka.bootstrap.servers", "host:port")
                .option("subscribe", "avro_queue")
                .load();

        // Cannot resolve method 'from_avro'...
        df.select(from_avro(col("value"), jsonFormatSchema)).writeStream().format("console")
                .outputMode("update")
                .start();


    }
}

pom.xml:

<dependencies>
    <dependency> 
        <groupId>org.apache.spark</groupId>
        <artifactId>spark-core_2.11</artifactId>
        <version>2.4.0</version>
    </dependency>
    <dependency>
        <groupId>org.apache.spark</groupId>
        <artifactId>spark-sql_2.11</artifactId>
        <version>2.4.0</version>
    </dependency>
    <dependency>
        <groupId>org.apache.spark</groupId>
        <artifactId>spark-avro_2.11</artifactId>
        <version>2.4.0</version>
    </dependency>
  <!-- more dependencies below -->

</dependencies>

It seems like Java is unable to import names from sql.avro.package.class

Tendril

Answer 1

It's because of the generated class names, importing it as import org.apache.spark.sql.avro.package$; and then using package$.MODULE$.from_avro(...) should work

Aludel

That worked, thanks! Interesting how org.apache.spark.sql.functions import works fine but avro one doesn't. – Tendril

@MaciejC The method from_avro is defined inside a package object while functions are inside a regular object. The regular objects generate similar byte code with Java static methods but there is no construct in Java similar to Scala package objects. – Aludel

Answer 2

You need to include spark-sql-avro in your pom.xml which is available at

https://mvnrepository.com/artifact/org.apache.spark/spark-sql-avro_2.11/2.4.0-palantir.28-1-gdf34e2d

Colwell

Thanks for your reply! That doesn't look like an official jar though? – Tendril