Package org.apache.commons.io.monitor
Class FileAlterationObserver
java.lang.Object
org.apache.commons.io.monitor.FileAlterationObserver
- All Implemented Interfaces:
Serializable
FileAlterationObserver represents the state of files below a root directory,
checking the file system and notifying listeners of create, change or
delete events.
To use this implementation:
- Create
FileAlterationListenerimplementation(s) that process the file/directory create, change and delete events - Register the listener(s) with a
FileAlterationObserverfor the appropriate directory. - Either register the observer(s) with a
FileAlterationMonitoror run manually.
Basic Usage
Create aFileAlterationObserver for the directory and register the listeners:
File directory = new File(FileUtils.current(), "src");
FileAlterationObserver observer = new FileAlterationObserver(directory);
observer.addListener(...);
observer.addListener(...);
To manually observe a directory, initialize the observer and invoked the
checkAndNotify() method as required:
// initialize
observer.init();
...
// invoke as required
observer.checkAndNotify();
...
observer.checkAndNotify();
...
// finished
observer.finish();
Alternatively, register the observer(s) with a FileAlterationMonitor,
which creates a new thread, invoking the observer at the specified interval:
long interval = ...
FileAlterationMonitor monitor = new FileAlterationMonitor(interval);
monitor.addObserver(observer);
monitor.start();
...
monitor.stop();
File Filters
This implementation can monitor portions of the file system by usingFileFilters to observe only the files and/or directories
that are of interest. This makes it more efficient and reduces the
noise from unwanted file system events.
Commons IO has a good range of useful, ready-made File Filter implementations for this purpose.
For example, to only observe 1) visible directories and 2) files with a ".java" suffix
in a root directory called "src" you could set up a FileAlterationObserver in the following
way:
// Create a FileFilter
IOFileFilter directories = FileFilterUtils.and(
FileFilterUtils.directoryFileFilter(),
HiddenFileFilter.VISIBLE);
IOFileFilter files = FileFilterUtils.and(
FileFilterUtils.fileFileFilter(),
FileFilterUtils.suffixFileFilter(".java"));
IOFileFilter filter = FileFilterUtils.or(directories, files);
// Create the File system observer and register File Listeners
FileAlterationObserver observer = new FileAlterationObserver(new File("src"), filter);
observer.addListener(...);
observer.addListener(...);
FileEntry
FileEntry represents the state of a file or directory, capturing
File attributes at a point in time. Custom implementations of
FileEntry can be used to capture additional properties that the
basic implementation does not support. The FileEntry.refresh(File)
method is used to determine if a file or directory has changed since the last
check and stores the current state of the File's properties.
Deprecating Serialization
Serialization is deprecated and will be removed in 3.0.
- Since:
- 2.0
- See Also:
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Constructor Summary
ConstructorsModifierConstructorDescriptionFileAlterationObserver(File directory) Constructs an observer for the specified directory.FileAlterationObserver(File directory, FileFilter fileFilter) Constructs an observer for the specified directory and file filter.FileAlterationObserver(File directory, FileFilter fileFilter, IOCase ioCase) Constructs an observer for the specified directory, file filter and file comparator.FileAlterationObserver(String directoryName) Constructs an observer for the specified directory.FileAlterationObserver(String directoryName, FileFilter fileFilter) Constructs an observer for the specified directory and file filter.FileAlterationObserver(String directoryName, FileFilter fileFilter, IOCase ioCase) Constructs an observer for the specified directory, file filter and file comparator.protectedFileAlterationObserver(FileEntry rootEntry, FileFilter fileFilter, IOCase ioCase) Constructs an observer for the specified directory, file filter and file comparator. -
Method Summary
Modifier and TypeMethodDescriptionvoidaddListener(FileAlterationListener listener) Adds a file system listener.voidChecks whether the file and its children have been created, modified or deleted.voiddestroy()Final processing.Returns the directory being observed.Returns the fileFilter.Returns the set of registered file system listeners.voidInitializes the observer.voidremoveListener(FileAlterationListener listener) Removes a file system listener.toString()Returns a String representation of this observer.
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Constructor Details
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FileAlterationObserver
Constructs an observer for the specified directory.- Parameters:
directory- the directory to observe
-
FileAlterationObserver
Constructs an observer for the specified directory and file filter.- Parameters:
directory- the directory to observefileFilter- The file filter or null if none
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FileAlterationObserver
Constructs an observer for the specified directory, file filter and file comparator.- Parameters:
directory- the directory to observefileFilter- The file filter or null if noneioCase- what case sensitivity to use comparing file names, null means system sensitive
-
FileAlterationObserver
Constructs an observer for the specified directory, file filter and file comparator.- Parameters:
rootEntry- the root directory to observefileFilter- The file filter or null if noneioCase- what case sensitivity to use comparing file names, null means system sensitive
-
FileAlterationObserver
Constructs an observer for the specified directory.- Parameters:
directoryName- the name of the directory to observe
-
FileAlterationObserver
Constructs an observer for the specified directory and file filter.- Parameters:
directoryName- the name of the directory to observefileFilter- The file filter or null if none
-
FileAlterationObserver
Constructs an observer for the specified directory, file filter and file comparator.- Parameters:
directoryName- the name of the directory to observefileFilter- The file filter or null if noneioCase- what case sensitivity to use comparing file names, null means system sensitive
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Method Details
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addListener
Adds a file system listener.- Parameters:
listener- The file system listener
-
checkAndNotify
Checks whether the file and its children have been created, modified or deleted. -
destroy
Final processing.- Throws:
Exception- if an error occurs
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getDirectory
Returns the directory being observed.- Returns:
- the directory being observed
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getFileFilter
Returns the fileFilter.- Returns:
- the fileFilter
- Since:
- 2.1
-
getListeners
Returns the set of registered file system listeners.- Returns:
- The file system listeners
-
initialize
Initializes the observer.- Throws:
Exception- if an error occurs
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removeListener
Removes a file system listener.- Parameters:
listener- The file system listener
-
toString
Returns a String representation of this observer.
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