io.ebean.tools.init.watch.WatchDir Maven / Gradle / Ivy
package io.ebean.tools.init.watch;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.HashMap;
import java.util.Map;
import static java.nio.file.LinkOption.NOFOLLOW_LINKS;
import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;
import static java.nio.file.StandardWatchEventKinds.ENTRY_DELETE;
import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;
import static java.nio.file.StandardWatchEventKinds.OVERFLOW;
/**
* Example to watch a directory (or tree) for changes to files.
*/
public class WatchDir implements Runnable {
private static final Logger log = LoggerFactory.getLogger(WatchDir.class);
private Thread workerThread;
private final WatchService watcher;
private final Map keys;
private final boolean recursive;
private boolean trace;
private final WatchDirCallback callback;
private final WatchDirSkip skipDir;
@SuppressWarnings("unchecked")
static WatchEvent cast(WatchEvent event) {
return (WatchEvent) event;
}
/**
* Register the given directory with the WatchService
*/
private void register(Path dir) throws IOException {
WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
if (trace) {
Path prev = keys.get(key);
if (prev == null) {
log.info("register: {}", dir);
} else {
if (!dir.equals(prev)) {
log.info("update: {} -> {}", prev, dir);
}
}
}
keys.put(key, dir);
}
/**
* Register the given directory, and all its sub-directories, with the WatchService.
*/
private void registerAll(final Path start) throws IOException {
Files.walkFileTree(start, new SimpleFileVisitor() {
@Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
if (skipDir != null && skipDir.skip(dir)) {
return FileVisitResult.SKIP_SUBTREE;
}
register(dir);
return FileVisitResult.CONTINUE;
}
});
}
/**
* Creates a WatchService and registers the given directory
*
* No WatchDirSkip specified.
*/
public WatchDir(Path dir, boolean recursive, WatchDirCallback callback) {
this(dir, recursive, callback, null);
}
/**
* Creates a WatchService and registers the given directory
*/
public WatchDir(Path dir, boolean recursive, WatchDirCallback callback, WatchDirSkip skipDir) {
try {
this.watcher = FileSystems.getDefault().newWatchService();
this.keys = new HashMap<>();
this.recursive = recursive;
this.callback = callback;
this.skipDir = skipDir;
if (recursive) {
log.info("Scanning {} ...", dir);
registerAll(dir);
log.info("Watching...");
} else {
register(dir);
}
// enable trace after initial registration
this.trace = true;
} catch (IOException e) {
throw new IllegalStateException(e);
}
}
public void start() {
workerThread = new Thread(this, "watcher");
workerThread.setDaemon(true);
workerThread.start();
}
/**
* Shutdown this listener.
*/
public void stop() {
try {
// try {
// workerThread.wait(1000);
// } catch (InterruptedException e) {
// // OK to ignore as expected to Interrupt for shutdown.
// }
workerThread.interrupt();
workerThread = null;
} catch (Exception e) {
log.error("Error stopping watcher", e);
}
}
@Override
public void run() {
processEvents();
}
/**
* Process all events for keys queued to the watcher
*/
public void processEvents() {
for (; ; ) {
// wait for key to be signalled
WatchKey key;
try {
key = watcher.take();
} catch (InterruptedException x) {
return;
}
Path dir = keys.get(key);
if (dir == null) {
log.error("WatchKey {} not recognized!!", key);
continue;
}
for (WatchEvent event : key.pollEvents()) {
WatchEvent.Kind kind = event.kind();
if (kind == OVERFLOW) {
log.error("OVERFLOW event is not handled");
continue;
}
// Context for directory entry event is the file name of entry
WatchEvent ev = cast(event);
Path name = ev.context();
Path child = dir.resolve(name);
// print out event
if (callback != null) {
callback.event(ev, child, event.kind().toString());
} else {
log.info(" event: {} {}", event.kind().name(), child);
}
// if directory is created, and watching recursively, then
// register it and its sub-directories
if (recursive && (kind == ENTRY_CREATE)) {
try {
if (skipDir != null && skipDir.skip(child)) {
} else {
if (Files.isDirectory(child, NOFOLLOW_LINKS)) {
registerAll(child);
}
}
} catch (IOException e) {
log.error("Error registering new directory", e);
}
}
}
// reset key and remove from set if directory no longer accessible
boolean valid = key.reset();
if (!valid) {
keys.remove(key);
// all directories are inaccessible
if (keys.isEmpty()) {
break;
}
}
}
}
}