develop-with-Wayang.md

This tutorial shows users how to import Wayang in their Java project using the maven.

Include the Wayang maven dependencies in your pom

        <dependency>
            <groupId>org.apache.wayang</groupId>
            <artifactId>wayang-core</artifactId>
            <version>0.7.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.wayang</groupId>
            <artifactId>wayang-basic</artifactId>
            <version>0.7.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.wayang</groupId>
            <artifactId>wayang-java</artifactId>
            <version>0.7.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.wayang</groupId>
            <artifactId>wayang-spark</artifactId>
            <version>0.7.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.wayang</groupId>
            <artifactId>wayang-api-scala-java</artifactId>
            <version>0.7.1</version>
        </dependency>

Include the Spark maven dependencies in your pom

        <dependency>
            <groupId>org.apache.spark</groupId>
            <artifactId>spark-core_2.12</artifactId>
            <version>${spark.version}</version>
        </dependency>

Other maven dependencies to consider

        <dependency>
            <groupId>org.scala-lang</groupId>
            <artifactId>scala-library</artifactId>
            <version>2.12.0</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-simple</artifactId>
            <version>1.7.13</version>
        </dependency>

A sample pom file can be found here.

Test WordCount

Create a Java class that contains the main method that runs the Wordcount

Here is a sample implementation getting as input the filename (e.g., file:/Projects/Wayang/test.txt)

public static void main(String[] args) {

        /* Create a Wayang context and specify the platforms Wayang will consider */
        WayangContext wayangContext = new WayangContext(new Configuration())
                .withPlugin(Java.basicPlugin())
                .withPlugin(Spark.basicPlugin());

        /* Get a plan builder */
        JavaPlanBuilder planBuilder = new JavaPlanBuilder(wayangContext)
                .withJobName("WordCount")
                .withUdfJarOf(WordCount.class);

        /* Start building the Apache WayangPlan */
        Collection<Tuple2<String, Integer>> wordcounts = planBuilder
                /* Read the text file */
                .readTextFile(args[0]).withName("Load file")

                /* Split each line by non-word characters */
                .flatMap(line -> Arrays.asList(line.split("\\W+")))
                .withName("Split words")

                /* Filter empty tokens */
                .filter(token -> !token.isEmpty())
                .withName("Filter empty words")
                /* you can also specify the desired platform per operator */
                //.withTargetPlatform(Java.platform())

                /* Attach counter to each word */
                .map(word -> new Tuple2<>(word.toLowerCase(), 1)).withName("To lower case, add counter")

                /* Sum up counters for every word. */
                .reduceByKey(
                        Tuple2::getField0,
                        (t1, t2) -> new Tuple2<>(t1.getField0(), t1.getField1() + t2.getField1())
                )
                .withName("Add counters")

                /* Execute the plan and collect the results */
                .collect();

        System.out.println(wordcounts);
}

A sample Java class file can be found here.