// see DirectoryScannerMXBean
public void scan() {
final ScanTask task;
synchronized (this) {
final LinkedList<File> list;
switch (state) {
case RUNNING:
case SCHEDULED:
throw new IllegalStateException(state.toString());
case STOPPED:
case COMPLETED:
// only accept to scan if state is STOPPED or COMPLETED.
list = new LinkedList<File>();
list.add(rootFile);
break;
default:
throw new IllegalStateException(String.valueOf(state));
}
// Create a new ScanTask object for our root directory file.
//
currentTask = task = new ScanTask(list, this);
// transient state... will be switched to RUNNING when
// task.execute() is called. This code could in fact be modified
// to use java.util.concurent.Future and, to push the task to
// an executor. We would then need to wait for the task to
// complete before returning. However, this wouldn't buy us
// anything - since this method should wait for the task to
// finish anyway: so why would we do it?
// As it stands, we simply call task.execute() in the current
// thread - brave and fearless readers may want to attempt the
// modification ;-)
//
setStateAndNotify(SCHEDULED);
}
task.execute();
}
// The actual scan logic. Switches state to RUNNING,
// and scan the list of given dirs.
// The list is a live object which is updated by this method.
// This would allow us to implement methods like "pause" and "resume",
// since all the info needed to resume would be in the list.
//
private void scan(ScanTask task, LinkedList<File> list) {
setStateAndNotify(RUNNING);
task.info = "In Progress";
try {
// The FileFilter will tell us which files match and which don't.
//
final FileFilter filter = config.buildFileFilter();
// We have two condition to end the loop: either the list is
// empty, meaning there's nothing more to scan, or the state of
// the DirectoryScanner was asynchronously switched to STOPPED by
// another thread, e.g. because someone called "stop" on the
// ScanManagerMXBean
//
while (!list.isEmpty() && state == RUNNING) {
// Get and remove the first element in the list.
//
final File current = list.poll();
// Increment number of file scanned.
task.scanned++;
// If 'current' is a file, it's already been matched by our
// file filter (see below): act on it.
// Note that for the first iteration of this loop, there will
// be one single file in the list: the root directory for this
// scanner.
//
if (current.isFile()) {
task.matching++;
actOn(current);
}
// If 'current' is a directory, then
// find files and directories that match the file filter
// in this directory
//
if (current.isDirectory()) {
// Gets matching files and directories
final File[] content = current.listFiles(filter);
if (content == null) continue;
// Adds all matching file to the list.
list.addAll(0, Arrays.asList(content));
}
}
// The loop terminated. If the list is empty, then we have
// completed our task. If not, then somebody must have called
// stop() on this directory scanner.
//
if (list.isEmpty()) {
task.info = "Successfully Completed";
setStateAndNotify(COMPLETED);
}
} catch (Exception x) {
// We got an exception: stop the scan
//
task.info = "Failed: " + x;
if (LOG.isLoggable(Level.FINEST)) LOG.log(Level.FINEST, "scan task failed: " + x, x);
else if (LOG.isLoggable(Level.FINE)) LOG.log(Level.FINE, "scan task failed: " + x);
setStateAndNotify(STOPPED);
} catch (Error e) {
// We got an Error:
// Should not happen unless we ran out of memory or
// whatever - don't even try to notify, but
// stop the scan anyway!
//
state = STOPPED;
task.info = "Error: " + e;
// rethrow error.
//
throw e;
}
}
// see DirectoryScannerMXBean
public String getCurrentScanInfo() {
final ScanTask currentOrLastTask = currentTask;
if (currentOrLastTask == null) return "Never Run";
return currentOrLastTask.getScanInfo();
}