Watchable

  • The Watchable interface allows objects to be registered with a WatchService for monitoring changes and events.

  • Objects can be registered with multiple watch services and registration is cancelled using the WatchKey's cancel method.

  • The register method registers the object with a WatchService and returns a WatchKey representing the registration, enabling event monitoring and modification.

  • Implementations of the Watchable interface should specify the supported events and relevant permissions for security.
public interface Watchable
Known Indirect Subclasses

An object that may be registered with a watch service so that it can be watched for changes and events.

This interface defines the register method to register the object with a WatchService returning a WatchKey to represent the registration. An object may be registered with more than one watch service. Registration with a watch service is cancelled by invoking the key's cancel method.

See Also

Public Method Summary

abstract WatchKey
register(WatchService watcher, Kind[]<?> events, Modifier... modifiers)
Registers an object with a watch service.
abstract WatchKey
register(WatchService watcher, Kind...<?> events)
Registers an object with a watch service.

Public Methods

public abstract WatchKey register (WatchService watcher, Kind[]<?> events, Modifier... modifiers)

Registers an object with a watch service.

If the file system object identified by this object is currently registered with the watch service then the watch key, representing that registration, is returned after changing the event set or modifiers to those specified by the events and modifiers parameters. Changing the event set does not cause pending events for the object to be discarded. Objects are automatically registered for the OVERFLOW event. This event is not required to be present in the array of events.

Otherwise the file system object has not yet been registered with the given watch service, so it is registered and the resulting new key is returned.

Implementations of this interface should specify the events they support.

Parameters
watcher the watch service to which this object is to be registered
events the events for which this object should be registered
modifiers the modifiers, if any, that modify how the object is registered
Returns
  • a key representing the registration of this object with the given watch service
Throws
UnsupportedOperationException if unsupported events or modifiers are specified
IllegalArgumentException if an invalid of combination of events are modifiers are specified
ClosedWatchServiceException if the watch service is closed
IOException if an I/O error occurs
SecurityException if a security manager is installed and it denies an unspecified permission required to monitor this object. Implementations of this interface should specify the permission checks.

public abstract WatchKey register (WatchService watcher, Kind...<?> events)

Registers an object with a watch service.

An invocation of this method behaves in exactly the same way as the invocation 

     watchable.register(watcher, events, new WatchEvent.Modifier[0]);

Parameters
watcher the watch service to which this object is to be registered
events the events for which this object should be registered
Returns
  • a key representing the registration of this object with the given watch service
Throws
UnsupportedOperationException if unsupported events are specified
IllegalArgumentException if an invalid of combination of events are specified
ClosedWatchServiceException if the watch service is closed
IOException if an I/O error occurs
SecurityException if a security manager is installed and it denies an unspecified permission required to monitor this object. Implementations of this interface should specify the permission checks.