code: protected static String getFileName(final Map<String, String> properties) {
  		String fileName = properties.get("file");
  		if (fileName == null) {
  			throw new IllegalArgumentException("File name is missing for file writer");
  		} else {
  			return fileName;
  		}
  	}
docs: Extracts the log file name from configuration.
  
  @param properties
  Configuration for writer
  @return Log file name
  @throws IllegalArgumentException
  Log file is not defined in configuration