File Listener/Monitor
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Key: IO-132
URL: https://issues.apache.org/jira/browse/IO-132
Project: Commons IO
Issue Type: New Feature
Reporter: Niall Pemberton
Assignee: Niall Pemberton
Fix For: 1.4
Attachments: FileListener.java, FileMonitor.java, FileObserver.java
Commons JCI has a "fam" (file alteration monitor) module[1] which provides a
listener for file and directory create/change/delete events. I have done some
work refactoring the JCI implementation and propose adding to to Commons IO.
There is already an existing request/propsal to add similar functionality in
IO-79 from Jim Harrington (which includes code).
There are IMO two main differences (IMO improvements) in this implementation
over exsiting JCI fam module:
1) It uses a matching array technique to compare previous and current directory
contents which minimizes object creation
2) FileFilters can be specified to monitor only portions of the file system,
ignoring files/directories of no interest. This is more efficient and reduces
the amount of noise from un-wanted file/directory events
>From a quick look at IO-79, the above also applies to that proposal.
>Additionally IMO the solution in IO-79 would benefit from been broken out from
>the two DirectoryPoller and FilePoller artifacts.
There are also some changes to the API specified in JCI's fam:
1) FileObserver (FilesystemAlterationObserver in fam) has additional init() and
destroy() methods
2) FileMonitor (FilesystemAlterationMonitor in fam) has
addObserver/removeObserver methods rather than addListener/removeListener
methods. The issue (IMO) with fam is that the monitor is fixed to the
FilesystemAlterationObserverImpl implementation, rather than any
FilesystemAlterationObserver implementation. Also the ability to specify file
filters means that there is a need to be able to add more than one observer for
the same root directory.
[1] http://svn.apache.org/repos/asf/commons/proper/jci/trunk/fam/
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