public HdfsSystemDescriptor withWriterClassName(String writerClassName) {
    this.writerClass = Optional.ofNullable(StringUtils.stripToNull(writerClassName));
    return this;
  }
The fully-qualified class name of the HdfsWriter subclass that will write for this system.
@param writerClassName writer class name.
@return this system descriptor
samza-hdfs/src/main/java/org/apache/samza/system/hdfs/descriptors/HdfsSystemDescriptor.java