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Java 1.8+ Library with tons of utility classes required in all projects
/*
* Copyright (C) 2014-2022 Philip Helger (www.helger.com)
* philip[at]helger[dot]com
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.helger.commons.io.watchdir;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.nio.file.ClosedWatchServiceException;
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.StandardWatchEventKinds;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import javax.annotation.Nonnull;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.helger.commons.ValueEnforcer;
import com.helger.commons.annotation.ReturnsMutableCopy;
import com.helger.commons.annotation.ReturnsMutableObject;
import com.helger.commons.callback.CallbackList;
import com.helger.commons.collection.ArrayHelper;
import com.helger.commons.collection.impl.CommonsHashMap;
import com.helger.commons.collection.impl.ICommonsMap;
import com.helger.commons.lang.GenericReflection;
import com.helger.commons.system.EOperatingSystem;
/**
* Generic directory watching service using the default JDK {@link WatchService}
* class.
*
* @author Philip Helger
* @since 9.0.0
*/
public class WatchDir implements AutoCloseable
{
private static final Logger LOGGER = LoggerFactory.getLogger (WatchDir.class);
private final WatchService m_aWatcher;
private final Path m_aStartDir;
private final boolean m_bRecursive;
private final boolean m_bRegisterRecursiveManually;
private final ICommonsMap m_aKeys = new CommonsHashMap <> ();
private final AtomicBoolean m_aProcessing = new AtomicBoolean (false);
private final CallbackList m_aCallbacks = new CallbackList <> ();
private WatchEvent.Modifier [] m_aModifiers = null;
/**
* Register the given directory with the WatchService
*
* @param aDir
* Directory to be watched. May not be null.
*/
private void _registerDir (@Nonnull final Path aDir) throws IOException
{
if (LOGGER.isDebugEnabled ())
LOGGER.debug ("Register directory " + aDir + (m_bRecursive && !m_bRegisterRecursiveManually ? " (recursively)" : ""));
final WatchEvent.Kind [] aKinds = new WatchEvent.Kind [] { StandardWatchEventKinds.ENTRY_CREATE,
StandardWatchEventKinds.ENTRY_DELETE,
StandardWatchEventKinds.ENTRY_MODIFY };
// throws exception when using with modifiers even if null
final WatchKey aKey = m_aModifiers != null ? aDir.register (m_aWatcher, aKinds, m_aModifiers) : aDir.register (m_aWatcher, aKinds);
m_aKeys.put (aKey, aDir);
}
/**
* Register the given directory, and all its sub-directories, with the
* WatchService.
*
* @param aStartDir
* The start directory to be iterated. May not be null.
*/
private void _registerDirRecursive (@Nonnull final Path aStartDir) throws IOException
{
// register directory and sub-directories
Files.walkFileTree (aStartDir, new SimpleFileVisitor ()
{
@Override
public FileVisitResult preVisitDirectory (final Path dir, final BasicFileAttributes attrs) throws IOException
{
_registerDir (dir);
return FileVisitResult.CONTINUE;
}
});
}
/**
* Creates a WatchService and registers the given directory
*
* @param aDir
* The directory to be watched. May not be null.
* @param bRecursive
* true to watch the directory recursive,
* false to watch just this directory.
* @throws IOException
* In case something goes wrong.
*/
public WatchDir (@Nonnull final Path aDir, final boolean bRecursive) throws IOException
{
ValueEnforcer.notNull (aDir, "Directory");
ValueEnforcer.isTrue (aDir.toFile ().isDirectory (), () -> "Provided path is not a directory: " + aDir);
m_aWatcher = FileSystems.getDefault ().newWatchService ();
m_aStartDir = aDir.toRealPath ();
m_bRecursive = bRecursive;
boolean bRegisterRecursiveManually = bRecursive;
// Windows only!
if (bRecursive && EOperatingSystem.WINDOWS.isCurrentOS ())
{
// Reflection, as this is for Windows/Oracle JDK only!
// Shortcut for com.sun.nio.file.ExtendedWatchEventModifier.FILE_TREE
final Class aClass = GenericReflection.getClassFromNameSafe ("com.sun.nio.file.ExtendedWatchEventModifier");
if (aClass != null)
{
// Use the special "register recursive" on Windows (enum constant
// "FILE_TREE")
@SuppressWarnings ("unchecked")
final Enum [] aEnumConstants = ((Class >) aClass).getEnumConstants ();
final Enum aFileTree = ArrayHelper.findFirst (aEnumConstants, x -> x.name ().equals ("FILE_TREE"));
if (aFileTree != null)
{
m_aModifiers = new WatchEvent.Modifier [] { (WatchEvent.Modifier) aFileTree };
bRegisterRecursiveManually = false;
}
}
}
m_bRegisterRecursiveManually = bRegisterRecursiveManually;
if (m_bRegisterRecursiveManually)
_registerDirRecursive (m_aStartDir);
else
_registerDir (m_aStartDir);
}
/**
* @return The modifiable callback list. Never null.
*/
@Nonnull
@ReturnsMutableObject
public CallbackList callbacks ()
{
return m_aCallbacks;
}
/**
* @return The start directory as specified in the constructor. Never
* null.
*/
@Nonnull
public Path getStartDirectory ()
{
return m_aStartDir;
}
/**
* @return true if this is a recursive listener,
* false if not.
*/
public boolean isRecursive ()
{
return m_bRecursive;
}
/**
* Close the watch directory service and stop processing.
*/
public void close () throws IOException
{
try
{
// Mark the processing to end
// This ends the processing started in #processEvents and will end any
// eventually running thread
stopProcessing ();
}
finally
{
m_aWatcher.close ();
}
}
/**
* Stop processing, if {@link #processEvents()} is active. This method is
* automatically called in {@link #close()}.
*/
public void stopProcessing ()
{
m_aProcessing.set (false);
}
/**
* Check if processing is active.
*
* @return true if event processing is active, false
* if not.
* @see #processEvents()
* @see #stopProcessing()
* @see #close()
*/
public boolean isProcessing ()
{
return m_aProcessing.get ();
}
/**
* Process all events for keys queued to the watcher. Call
* {@link #stopProcessing()} or {@link #close()} to stop processing within a
* reasonable time. This method should run in a separate thread, as it
* contains an infinite loop! Usually you don't call this method manually.
*
* @see #runAsync()
*/
public void processEvents ()
{
if (LOGGER.isInfoEnabled ())
LOGGER.info ("Start processing directory change events in '" + m_aStartDir + "'" + (m_bRecursive ? " (recursively)" : ""));
if (m_aCallbacks.isEmpty ())
throw new IllegalStateException ("No callback registered for watching directory changes in " + m_aStartDir);
m_aProcessing.set (true);
while (m_aProcessing.get ())
{
// wait max 1 sec for key to be signaled
WatchKey aKey;
try
{
aKey = m_aWatcher.poll (1, TimeUnit.SECONDS);
}
catch (final InterruptedException x)
{
// Watcher was interrupted - stop loop
Thread.currentThread ().interrupt ();
break;
}
catch (final ClosedWatchServiceException x)
{
// Watcher was interrupted - stop loop
break;
}
if (aKey == null)
{
// Nothing here within time limit - try again
continue;
}
final Path aSrcDir = m_aKeys.get (aKey);
if (aSrcDir == null)
{
if (LOGGER.isErrorEnabled ())
LOGGER.error ("WatchKey " + aKey + " not recognized!!");
continue;
}
for (final WatchEvent aEvent : aKey.pollEvents ())
{
final WatchEvent.Kind aKind = aEvent.kind ();
if (aKind == StandardWatchEventKinds.OVERFLOW)
{
if (LOGGER.isWarnEnabled ())
LOGGER.warn ("Got an overflow event on directory " + aSrcDir);
continue;
}
// Context for directory entry event is the file name of entry
final Path aEventPath = (Path) aEvent.context ();
final Path aFullEventPath = aSrcDir.resolve (aEventPath);
// print out event
EWatchDirAction eAction;
if (aKind == StandardWatchEventKinds.ENTRY_CREATE)
eAction = EWatchDirAction.CREATE;
else
if (aKind == StandardWatchEventKinds.ENTRY_DELETE)
eAction = EWatchDirAction.DELETE;
else
if (aKind == StandardWatchEventKinds.ENTRY_MODIFY)
eAction = EWatchDirAction.MODIFY;
else
{
eAction = null;
if (LOGGER.isErrorEnabled ())
LOGGER.error ("Unsupported event kind: " + aKind + " on path: '" + aFullEventPath + "'");
}
if (eAction != null)
{
// Main callback invocation
m_aCallbacks.forEach (x -> x.onAction (eAction, aFullEventPath));
}
// if directory is created, and watching recursively, then
// register it and its sub-directories
if (m_bRecursive && aKind == StandardWatchEventKinds.ENTRY_CREATE)
{
try
{
// Better performance
if (aFullEventPath.toFile ().isDirectory ())
{
if (m_bRegisterRecursiveManually)
_registerDirRecursive (aFullEventPath);
else
if (aFullEventPath.equals (aSrcDir))
{
// The main directory was altered (e.g. renamed) so
// re-register
_registerDir (aFullEventPath);
}
}
}
catch (final IOException x)
{
throw new UncheckedIOException ("Error registering handler ony the fly for " + aFullEventPath, x);
}
}
}
// reset key and remove from set if directory no longer accessible
final boolean bValid = aKey.reset ();
if (!bValid)
{
if (LOGGER.isInfoEnabled ())
LOGGER.info ("Unregister directory " + aSrcDir);
m_aKeys.remove (aKey);
// all directories are inaccessible
// -> leave main loop
if (m_aKeys.isEmpty ())
break;
}
}
if (LOGGER.isInfoEnabled ())
LOGGER.info ("Finished processing directory change events in '" + m_aStartDir + "'");
}
/**
* Call this method to process events. This method creates a background thread
* than runs {@link #processEvents()} and performs the heavy lifting.
*/
public void runAsync ()
{
runAsyncAndReturn ();
}
/**
* Call this method to process events. This method creates a background thread
* than runs {@link #processEvents()} and performs the heavy lifting.
*
* @return The created {@link Thread} that can also be stopped again if not
* needed anymore.
* @since 10.1.5
*/
@Nonnull
public Thread runAsyncAndReturn ()
{
final Thread aThread = new Thread (this::processEvents, "WatchDir-" + m_aStartDir + "-" + ThreadLocalRandom.current ().nextInt ());
aThread.setDaemon (true);
aThread.start ();
return aThread;
}
/**
* Static factory method to create a simple {@link WatchDir} instance that
* already spawned an Thread to listen. To close the thread call the
* {@link WatchDir#close()} method.
*
* @param aDir
* The directory to be watched. May not be null.
* @param bRecursive
* true to watch the directory recursive,
* false to watch just this directory.
* @param aCallback
* The callback to be invoked if something changed. May not be
* null.
* @return The newly created {@link WatchDir} instance and never
* null.
* @throws IOException
* In case something goes wrong.
*/
@Nonnull
@ReturnsMutableCopy
public static WatchDir createAsyncRunningWatchDir (@Nonnull final Path aDir,
final boolean bRecursive,
@Nonnull final IWatchDirCallback aCallback) throws IOException
{
final WatchDir ret = new WatchDir (aDir, bRecursive);
ret.callbacks ().add (aCallback);
ret.runAsync ();
return ret;
}
}