@Override
public void onStart( final FileAlterationObserver observer ) {

	if( this.alreadyStarted.getAndSet( true ))
		return;

	this.logger.fine("Initial provisioning of templates...");
	final Collection<File> templateFiles = FileUtils.listFiles(
			this.templateDir,

			// Find readable template files.
			FileFilterUtils.and(
					FileFilterUtils.suffixFileFilter( ".tpl" ),
					CanReadFileFilter.CAN_READ),

			// Directory filter: go through the root template directory and its direct children.
			new TemplateDirectoryFileFilter( this.templateDir ));

	process( templateFiles );
}
 

/**
 * Constructor.
 * @param manager the templating manager, to which event handling is delegated.
 * @param templateDir the templates directory to watch.
 * @param pollInterval the poll interval.
 * @throws IOException if there is a problem watching the template directory.
 */
public TemplateWatcher( final TemplatingManager manager, final File templateDir, final long pollInterval ) {
	this.templateDir = templateDir;

	// Register the custom helpers.
	this.handlebars.registerHelper( AllHelper.NAME, new AllHelper());
	this.handlebars.registerHelper( IsKeyHelper.NAME, new IsKeyHelper());

	// Pretty formatting
	this.handlebars.prettyPrint( true );

	// Create the observer, register this object as the event listener.
	FileFilter fileFilter = FileFilterUtils.or(
			FileFilterUtils.and(
					FileFilterUtils.fileFileFilter(),
					FileFilterUtils.suffixFileFilter( ".tpl" ),
					CanReadFileFilter.CAN_READ,
					new TemplateFileFilter(templateDir)),
			FileFilterUtils.and(
					FileFilterUtils.directoryFileFilter(),
					CanReadFileFilter.CAN_READ,
					new TemplateSubDirectoryFileFilter(templateDir))
	);

	FileAlterationObserver observer = new FileAlterationObserver( this.templateDir, fileFilter );
	observer.addListener( this );

	// Create the monitor.
	this.monitor = new FileAlterationMonitor( pollInterval, observer );
	this.monitor.setThreadFactory( THREAD_FACTORY );

	this.manager = manager;
	this.logger.fine( "Template watcher is watching "
			+ this.templateDir
			+ " with an interval of " + pollInterval + " ms." );
}
 

/**
 * Returns list of files matches specified regex in specified directories
 *
 * @param regex       to match file names
 * @param directories to find
 * @return list of files matches specified regex in specified directories
 */
public static List<File> listFilesByRegex(String regex, File... directories) {
    return listFiles(directories,
            new RegexFileFilter(regex),
            CanReadFileFilter.CAN_READ);
}