Error: Failed to Load Class main using Spark-submit

Question

My Code is below

import org.apache.spark.SparkContext;
import org.apache.spark.SparkConf;
object WordCounter {
   def main(args: Array[String]) {
     val conf = new SparkConf().setAppName("Word Counter").setMaster("local")
     val sc = new SparkContext(conf)
     val textFile = sc.textFile("C:/spark/README.md")
     val tokenizedFileData = textFile.flatMap(line=>line.split(" "))
     val countPrep = tokenizedFileData.map(word=>(word,1))
     val counts = countPrep.reduceByKey((accumValue,newValue)=> accumValue + newValue)
     val sortedCounts = counts.sortBy(kvPair=>kvPair._2,false)
     sortedCounts.saveAsTextFile("C:/Data/WordCountViaApp")
   }
}

Can someone please help?

C:\Users\workspace\SparkInScala>spark-submit --class "WordCounter" "C:\Users\workspace\SparkInScala\target\scala-2.12\sparkinscala_2.12-0.1.0-SNAPSHOT.jar" Error: Failed to load class WordCounter.

Answer 1

I meet the same problem before.

I'm using Maven plug-in of idea to develop Spark Program.Here is my pom.xml

<build>
    <plugins>
        <plugin>
            <groupId>net.alchim31.maven</groupId>
            <artifactId>scala-maven-plugin</artifactId>
            <version>3.2.2</version>
            <executions>
                <execution>
                    <id>compile-scala</id>
                    <phase>compile</phase>
                    <goals>
                        <goal>add-source</goal>
                        <goal>compile</goal>
                    </goals>
                </execution>
                <execution>
                    <id>test-compile-scala</id>
                    <phase>test-compile</phase>
                    <goals>
                        <goal>add-source</goal>
                        <goal>testCompile</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <scalaVersion>2.12.11</scalaVersion>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.5.1</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
        <plugin>
            <artifactId>maven-assembly-plugin</artifactId>
            <configuration>
                <descriptorRefs>
                    <descriptorRef>jar-with-dependencies</descriptorRef>
                </descriptorRefs>
                <archive>
                    <manifest>
                        <mainClass>testConf</mainClass>
                    </manifest>
                </archive>
            </configuration>
            <executions>
                <execution>
                    <id>make-assembly</id>
                    <phase>package</phase>
                    <goals>
                        <goal>assembly</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>

        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>exec-maven-plugin</artifactId>
            <version>1.6.0</version>
            <executions>
                <execution>
                    <goals>
                        <goal>exec</goal>
                    </goals>
                </execution>
            </executions>
            <configuration>
                <executable>java</executable>
                <includeProjectDependencies>true</includeProjectDependencies>
                <includePluginDependencies>false</includePluginDependencies>
                <classpathScope>compile</classpathScope>
                <mainClass>testConf</mainClass>
            </configuration>
        </plugin>
    </plugins>

</build>

you can try it by replace the mainClass label "testConf" to your class name,and scala version etc.

Answer 2

If you want to use SBT then you have to specify which main method to start the execution.

Main-Class: com.WordCounter.main

That above tells SBT to add the line to the META-INF/MANIFEST.MF file in your JAR when you run sbt package.

When running your application with SBT,

sbt "run-main com.WordCounter.main"

Also, as pointed out by Wu, Maven will do the job as well.

Answer 3

You should include the full path of the.scala class/file that you want to execute. For example if your class resides in a folder structure like com/example/xyz.scala then your command should be: "--class com.example.xyz"

Answer 4

This is working fine after making changes in build.sbt file with appropriate versions. I no more see the error Failed to Load class.