Package net.morimekta.util

Class FileWatcher

java.lang.Object

net.morimekta.util.FileWatcher

All Implemented Interfaces:

java.lang.AutoCloseable

public class FileWatcher
extends java.lang.Object
implements java.lang.AutoCloseable

File watcher helper for use with simple callbacks. It monitors two types of changes: Actual file changes, and symlink changes. Note that whenever a file or symlink is added to the whole, it will be monitored at least until the file or symlink is deleted. There are essentially two types of watchers. File specific watchers will always resolve back to the "requested" file, and it is triggered whenever any of:

• The current canonical file content changed.
• The link starts pointing to a different file, this is only calculated based on the file being a symlink, or being in a symlinked directory. Everything else is treated as canonical locations.

So if this is the case (ref configMaps in kubernetes):

 /volume/map/..2018-01/config.txt (old file)
 /volume/map/..2018-02/config.txt (new file)
 /volume/map/..data     -> symlink to '..2018-01'
 /volume/map/config.txt -> symlink to '..data/config.txt'
 

If you listen to '/volume/map/config.txt', then you are notified if:

• '/volume/map/..2018-01/config.txt' is changed
• '/volume/map/..data' symlink is updated to '..2018-02'
• '/volume/map/config.txt' symlink is updated to '..2018-02/config.txt'

The important case here is the middle one, as this is the way kubernetes handles its configMaps and Secrets.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	FileWatcher.Listener
static interface	FileWatcher.Watcher	Deprecated. Use FileWatcher.Listener instead.

Constructor Summary

Constructors

Modifier	Constructor	Description
	FileWatcher()	Create a FileWatcher with default watch service.
	FileWatcher(java.nio.file.WatchService watchService)	Create a FileWatcher using the provided watch service.
protected	FileWatcher(java.nio.file.WatchService watchService, java.util.concurrent.ExecutorService watcherExecutor, java.util.concurrent.ExecutorService callbackExecutor)

Method Summary

Modifier and Type	Method	Description
void	addWatcher(java.io.File file, FileWatcher.Listener watcher)	Deprecated. Use addWatcher(Path, Listener)
void	addWatcher(java.io.File file, FileWatcher.Watcher watcher)	Deprecated. Use addWatcher(Path, Listener)
void	addWatcher(java.nio.file.Path file, FileWatcher.Listener watcher)	Start watching file path and notify watcher for updates on that file.
void	addWatcher(java.nio.file.Path file, FileWatcher.Watcher watcher)	Deprecated.
void	addWatcher(FileWatcher.Listener watcher)	Deprecated. Use addWatcher(File, Listener)
void	addWatcher(FileWatcher.Watcher watcher)	Deprecated. Use addWatcher(File, Listener)
void	close()
boolean	removeWatcher(FileWatcher.Listener watcher)	Remove a watcher from the list of listeners.
boolean	removeWatcher(FileWatcher.Watcher watcher)	Deprecated.
void	startWatching(java.io.File file)	Deprecated. Use addWatcher(File, Listener) or weakAddWatcher(File, Listener)
void	stopWatching(java.io.File file)	Deprecated. Use removeWatcher(Listener) and let it clean up watched files itself.
void	weakAddWatcher(java.io.File file, FileWatcher.Listener watcher)	Deprecated. Use weakAddWatcher(Path, Listener)
void	weakAddWatcher(java.io.File file, FileWatcher.Watcher watcher)	Deprecated. Use weakAddWatcher(Path, Listener)
void	weakAddWatcher(java.nio.file.Path file, FileWatcher.Listener watcher)	Start watching file path and notify watcher for updates on that file.
void	weakAddWatcher(java.nio.file.Path file, FileWatcher.Watcher watcher)	Deprecated.
void	weakAddWatcher(FileWatcher.Listener watcher)	Deprecated. Use weakAddWatcher(File, Listener).
void	weakAddWatcher(FileWatcher.Watcher watcher)	Deprecated. Use weakAddWatcher(File, Listener).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FileWatcher

public FileWatcher()

Create a FileWatcher with default watch service.

FileWatcher

public FileWatcher(java.nio.file.WatchService watchService)

Create a FileWatcher using the provided watch service.

Parameters:

watchService - Watcher service to use.

FileWatcher

protected FileWatcher(java.nio.file.WatchService watchService,
                      java.util.concurrent.ExecutorService watcherExecutor,
                      java.util.concurrent.ExecutorService callbackExecutor)

Method Detail

addWatcher

@Deprecated
public void addWatcher(java.io.File file,
                       FileWatcher.Watcher watcher)

Deprecated.

Use addWatcher(Path, Listener)

Start watching file path and notify watcher for updates on that file.

Parameters:

file - The file path to watch.

watcher - The watcher to be notified.

addWatcher

@Deprecated
public void addWatcher(java.io.File file,
                       FileWatcher.Listener watcher)

Deprecated.

Use addWatcher(Path, Listener)

Start watching file path and notify watcher for updates on that file.

Parameters:

file - The file path to watch.

watcher - The watcher to be notified.

addWatcher

@Deprecated
public void addWatcher(java.nio.file.Path file,
                       FileWatcher.Watcher watcher)

Deprecated.

Start watching file path and notify watcher for updates on that file.

Parameters:

file - The file path to watch.

watcher - The watcher to be notified.

addWatcher

public void addWatcher(java.nio.file.Path file,
                       FileWatcher.Listener watcher)

Start watching file path and notify watcher for updates on that file.

Parameters:

file - The file path to watch.

watcher - The watcher to be notified.

addWatcher

@Deprecated
public void addWatcher(FileWatcher.Watcher watcher)

Deprecated.

Use addWatcher(File, Listener)

Add a file watcher that is persistent. If the reference from the file watcher to the watcher itself should not prevent garbage collection, use the weakAddWatcher(Listener) method.

Parameters:

watcher - The watcher to add.

addWatcher

@Deprecated
public void addWatcher(FileWatcher.Listener watcher)

Deprecated.

Use addWatcher(File, Listener)

Add a file watcher that is persistent. If the reference from the file watcher to the watcher itself should not prevent garbage collection, use the weakAddWatcher(Listener) method.

Parameters:

watcher - The watcher to add.

weakAddWatcher

@Deprecated
public void weakAddWatcher(java.io.File file,
                           FileWatcher.Watcher watcher)

Deprecated.

Use weakAddWatcher(Path, Listener)

Start watching file path and notify watcher for updates on that file. The watcher will be kept in a weak reference and will allow GC to delete the instance.

Parameters:

file - The file path to watch.

watcher - The watcher to be notified.

weakAddWatcher

@Deprecated
public void weakAddWatcher(java.io.File file,
                           FileWatcher.Listener watcher)

Deprecated.

Use weakAddWatcher(Path, Listener)

Start watching file path and notify watcher for updates on that file. The watcher will be kept in a weak reference and will allow GC to delete the instance.

Parameters:

file - The file path to watch.

watcher - The watcher to be notified.

weakAddWatcher

@Deprecated
public void weakAddWatcher(java.nio.file.Path file,
                           FileWatcher.Watcher watcher)

Deprecated.

Start watching file path and notify watcher for updates on that file. The watcher will be kept in a weak reference and will allow GC to delete the instance.

Parameters:

file - The file path to watch.

watcher - The watcher to be notified.

weakAddWatcher

public void weakAddWatcher(java.nio.file.Path file,
                           FileWatcher.Listener watcher)

Start watching file path and notify watcher for updates on that file. The watcher will be kept in a weak reference and will allow GC to delete the instance.

Parameters:

file - The file path to watch.

watcher - The watcher to be notified.

weakAddWatcher

@Deprecated
public void weakAddWatcher(FileWatcher.Watcher watcher)

Deprecated.

Use weakAddWatcher(File, Listener).

Add a non-persistent file watcher.

Parameters:

watcher - The watcher to add.

weakAddWatcher

@Deprecated
public void weakAddWatcher(FileWatcher.Listener watcher)

Deprecated.

Use weakAddWatcher(File, Listener).

Add a non-persistent file watcher.

Parameters:

watcher - The watcher to add.

removeWatcher

@Deprecated
public boolean removeWatcher(FileWatcher.Watcher watcher)

Deprecated.

Remove a watcher from the list of listeners.

Parameters:

watcher - The watcher to be removed.

Returns:

True if the watcher was removed from the list.

removeWatcher

public boolean removeWatcher(FileWatcher.Listener watcher)

Remove a watcher from the list of listeners.

Parameters:

watcher - The watcher to be removed.

Returns:

True if the watcher was removed from the list.

startWatching

@Deprecated
public void startWatching(java.io.File file)

Deprecated.

Use addWatcher(File, Listener) or weakAddWatcher(File, Listener)

Start watching a specific file. Note that this will watch the file as seen in the directory as it is pointed to. This means that if the file itself is a symlink, then change events will notify changes to the symlink definition, not the content of the file.

Parameters:

file - The file to be watched.

stopWatching

@Deprecated
public void stopWatching(java.io.File file)

Deprecated.

Use removeWatcher(Listener) and let it clean up watched files itself.

Stop watching a specific file.

Parameters:

file - The file to be watched.

close

public void close()

Specified by:

close in interface java.lang.AutoCloseable