- private static final Log LOG = LogFactory.getLog(DirectoryMonitor.class);
-
- public static interface Listener {
-
- void fileChanged(File aFile);
-
- void fileCreated(File aFile);
-
- void fileDeleted(File aFile);
- };
-
- private File _directory;
- private FileFilter _filter;
- private Listener _listener;
- private Map<File, Date> _contents;
-
- public DirectoryMonitor(File aDirectory, FileFilter aFilefilter,
- Listener aListener) {
- _directory = aDirectory;
- if (!_directory.isDirectory()) {
- throw new IllegalArgumentException("Directory '" + _directory
- + "' does not exist");
- }
- _filter = aFilefilter;
- _listener = aListener;
- _contents = new HashMap<File, Date>();
- }
-
- /**
- * Polls the directory for changes and notifies the listener of any changes.
- * In case of any exceptions thrown by the listener while handling the changes,
- * the next call to this method will invoked the listeners again for the same changes.
- */
- public void poll() {
- LOG.debug("Polling " + _directory);
- Map<File, Date> newContents = new HashMap<File, Date>();
- File[] files = _directory.listFiles(_filter);
-
- // Check deleted files.
- Set<File> deletedFiles = new HashSet<File>(_contents.keySet());
- for (File file : files) {
- if (file.isFile()) {
- if (_contents.containsKey(file)) {
- deletedFiles.remove(file);
- }
- }
- }
- for (File file : deletedFiles) {
- _listener.fileDeleted(file);
- }
-
- for (File file : files) {
- if (file.isFile()) {
- if (_contents.containsKey(file)) {
- Date oldDate = _contents.get(file);
- if (file.lastModified() != oldDate.getTime()) {
- _listener.fileChanged(file);
- } else {
- // No change.
- }
- newContents.put(file, new Date(file.lastModified()));
- } else {
- _listener.fileCreated(file);
- newContents.put(file, new Date(file.lastModified()));
- }
- }
- }
-
- _contents = newContents;
- }