title: Q: No appenders could be found for logger (org.apache.spark.deploy.SparkSubmit$$anon$2) after spark-submit
body: <p>Quick Start step by step with Apache Spark
  but finally show this warn message</p>
  
  <pre><code>20/05/25 09:43:05 WARN NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
  log4j:WARN No appenders could be found for logger (org.apache.spark.deploy.SparkSubmit$$anon$2).
  log4j:WARN Please initialize the log4j system properly.
  log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
  </code></pre>
  
  <p>My code is</p>
  
  <pre><code>package firstmaven;
  
  import org.apache.spark.sql.SparkSession;
  import org.apache.spark.sql.Dataset;
  /**
   * Hello world!
   *
   */
  public class App 
  {
      public static void main( String[] args )
      {
          String logFile = "/data/spark/README.md";
          SparkSession spark = SparkSession.builder().appName("Simple Application")
                              .config("spark.master","local").getOrCreate();
          Dataset&lt;String&gt; logData = spark.read().textFile(logFile).cache();
          long numAs = logData.filter(s -&gt; s.contains("a")).count();
          long numBs = logData.filter(s -&gt; s.contains("b")).count();
          System.out.println("Lines with a: " + numAs + ", lines with b: " + numBs);
  
          System.out.println("Hello world");
  
          spark.stop();
      }
  }
  </code></pre>
  
  <p>What should I do to let it work ? Thanks.</p>