Class FileAlterationObserver

java.lang.Object
org.apache.commons.io.monitor.FileAlterationObserver
All Implemented Interfaces:
Serializable
public class FileAlterationObserver extends Object implements 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:

Basic Usage

Create a FileAlterationObserver 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 using FileFilters 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:

  • Constructor Details

    • FileAlterationObserver

      @Deprecated public FileAlterationObserver(File directory)
      Deprecated.
      Use builder().
      Constructs an observer for the specified directory.
      Parameters:
      directory - the directory to observe.

    • FileAlterationObserver

      @Deprecated public FileAlterationObserver(File directory, FileFilter fileFilter)
      Deprecated.
      Use builder().
      Constructs an observer for the specified directory and file filter.
      Parameters:
      directory - The directory to observe.
      fileFilter - The file filter or null if none.

    • FileAlterationObserver

      @Deprecated public FileAlterationObserver(File directory, FileFilter fileFilter, IOCase ioCase)
      Deprecated.
      Use builder().
      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.

    • FileAlterationObserver

      protected FileAlterationObserver(FileEntry rootEntry, 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.

    • FileAlterationObserver

      @Deprecated public FileAlterationObserver(String directoryName)
      Deprecated.
      Use builder().
      Constructs an observer for the specified directory.
      Parameters:
      directoryName - the name of the directory to observe.

    • FileAlterationObserver

      @Deprecated public FileAlterationObserver(String directoryName, FileFilter fileFilter)
      Deprecated.
      Use builder().
      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.

    • FileAlterationObserver

      @Deprecated public FileAlterationObserver(String directoryName, FileFilter fileFilter, IOCase ioCase)
      Deprecated.
      Use builder().
      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.

  • Method Details