Class FileAlterationObserver
- java.lang.Object
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- org.apache.commons.io.monitor.FileAlterationObserver
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- All Implemented Interfaces:
java.io.Serializable
public class FileAlterationObserver extends java.lang.Object implements java.io.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
FileAlterationListener
implementation(s) that process the file/directory create, change and delete events - Register the listener(s) with a
FileAlterationObserver
for the appropriate directory. - Either register the observer(s) with a
FileAlterationMonitor
or 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 usingFileFilter
s 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, capturingFile
attributes at a point in time. Custom implementations ofFileEntry
can be used to capture additional properties that the basic implementation does not support. TheFileEntry.refresh(File)
method is used to determine if a file or directory has changed since the last check and stores the current state of theFile
's properties.Deprecating Serialization
Serialization is deprecated and will be removed in 3.0.
- Since:
- 2.0
- See Also:
FileAlterationListener
,FileAlterationMonitor
, Serialized Form
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Nested Class Summary
Nested Classes Modifier and Type Class Description static class
FileAlterationObserver.Builder
Builds instances ofFileAlterationObserver
.
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Constructor Summary
Constructors Modifier Constructor Description FileAlterationObserver(java.io.File directory)
Deprecated.Usebuilder()
.FileAlterationObserver(java.io.File directory, java.io.FileFilter fileFilter)
Deprecated.Usebuilder()
.FileAlterationObserver(java.io.File directory, java.io.FileFilter fileFilter, IOCase ioCase)
Deprecated.Usebuilder()
.FileAlterationObserver(java.lang.String directoryName)
Deprecated.Usebuilder()
.FileAlterationObserver(java.lang.String directoryName, java.io.FileFilter fileFilter)
Deprecated.Usebuilder()
.FileAlterationObserver(java.lang.String directoryName, java.io.FileFilter fileFilter, IOCase ioCase)
Deprecated.Usebuilder()
.protected
FileAlterationObserver(FileEntry rootEntry, java.io.FileFilter fileFilter, IOCase ioCase)
Constructs an observer for the specified directory, file filter and file comparator.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
addListener(FileAlterationListener listener)
Adds a file system listener.static FileAlterationObserver.Builder
builder()
Creates a new builder.void
checkAndNotify()
Checks whether the file and its children have been created, modified or deleted.void
destroy()
Final processing.java.io.File
getDirectory()
Returns the directory being observed.java.io.FileFilter
getFileFilter()
Returns the fileFilter.java.lang.Iterable<FileAlterationListener>
getListeners()
Returns the set of registered file system listeners.void
initialize()
Initializes the observer.void
removeListener(FileAlterationListener listener)
Removes a file system listener.java.lang.String
toString()
Returns a String representation of this observer.
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Constructor Detail
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FileAlterationObserver
@Deprecated public FileAlterationObserver(java.io.File directory)
Deprecated.Usebuilder()
.Constructs an observer for the specified directory.- Parameters:
directory
- the directory to observe.
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FileAlterationObserver
@Deprecated public FileAlterationObserver(java.io.File directory, java.io.FileFilter fileFilter)
Deprecated.Usebuilder()
.Constructs an observer for the specified directory and file filter.- Parameters:
directory
- The directory to observe.fileFilter
- The file filter or null if none.
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FileAlterationObserver
@Deprecated public FileAlterationObserver(java.io.File directory, java.io.FileFilter fileFilter, IOCase ioCase)
Deprecated.Usebuilder()
.Constructs an observer for the specified directory, file filter and file comparator.- Parameters:
directory
- The directory to observe.fileFilter
- The file filter or null if none.ioCase
- What case sensitivity to use comparing file names, null means system sensitive.
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FileAlterationObserver
protected FileAlterationObserver(FileEntry rootEntry, java.io.FileFilter fileFilter, IOCase ioCase)
Constructs an observer for the specified directory, file filter and file comparator.- Parameters:
rootEntry
- The root directory to observe.fileFilter
- The file filter or null if none.ioCase
- What case sensitivity to use comparing file names, null means system sensitive.
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FileAlterationObserver
@Deprecated public FileAlterationObserver(java.lang.String directoryName)
Deprecated.Usebuilder()
.Constructs an observer for the specified directory.- Parameters:
directoryName
- the name of the directory to observe.
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FileAlterationObserver
@Deprecated public FileAlterationObserver(java.lang.String directoryName, java.io.FileFilter fileFilter)
Deprecated.Usebuilder()
.Constructs an observer for the specified directory and file filter.- Parameters:
directoryName
- the name of the directory to observe.fileFilter
- The file filter or null if none.
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FileAlterationObserver
@Deprecated public FileAlterationObserver(java.lang.String directoryName, java.io.FileFilter fileFilter, IOCase ioCase)
Deprecated.Usebuilder()
.Constructs an observer for the specified directory, file filter and file comparator.- Parameters:
directoryName
- the name of the directory to observe.fileFilter
- The file filter or null if none.ioCase
- what case sensitivity to use comparing file names, null means system sensitive.
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Method Detail
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builder
public static FileAlterationObserver.Builder builder()
Creates a new builder.- Returns:
- a new builder.
- Since:
- 2.18.0
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addListener
public void addListener(FileAlterationListener listener)
Adds a file system listener.- Parameters:
listener
- The file system listener.
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checkAndNotify
public void checkAndNotify()
Checks whether the file and its children have been created, modified or deleted.
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destroy
public void destroy() throws java.lang.Exception
Final processing.- Throws:
java.lang.Exception
- if an error occurs.
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getDirectory
public java.io.File getDirectory()
Returns the directory being observed.- Returns:
- the directory being observed.
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getFileFilter
public java.io.FileFilter getFileFilter()
Returns the fileFilter.- Returns:
- the fileFilter.
- Since:
- 2.1
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getListeners
public java.lang.Iterable<FileAlterationListener> getListeners()
Returns the set of registered file system listeners.- Returns:
- The file system listeners
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initialize
public void initialize() throws java.lang.Exception
Initializes the observer.- Throws:
java.lang.Exception
- if an error occurs.
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removeListener
public void removeListener(FileAlterationListener listener)
Removes a file system listener.- Parameters:
listener
- The file system listener.
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toString
public java.lang.String toString()
Returns a String representation of this observer.- Overrides:
toString
in classjava.lang.Object
- Returns:
- a String representation of this observer.
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