I have a file I need to read several times from. I have to open the InputStream to the same file in sequence. Now I wonder if that file can be locked for the whole os as long as a specific portion of the Java application is running?
I want to prevent 3 from happening:
- Reading file
example.txtfrom myApp.java - Stop Reading file
example.txt - Other process writes file (i.e.
echo "foo" >> example.txt) - Reading file
example.txtfrom myApp.java
As far as I understand java.nio.FileChannel lock does only lock access to a file for other JVM applications.
The Java API for this is java.nio.channels.FileLock. You say:
As far as I understand
java.nio.FileChannellock does only lock access to a file for other JVM applications.
That understanding is incorrect. From the documentation of FileLock:
Platform dependencies
This file-locking API is intended to map directly to the native locking facility of the underlying operating system. Thus the locks held on a file should be visible to all programs that have access to the file, regardless of the language in which those programs are written [emphasis added].
Whether or not a lock actually prevents another program from accessing the content of the locked region is system-dependent and therefore unspecified. The native file-locking facilities of some systems are merely advisory, meaning that programs must cooperatively observe a known locking protocol in order to guarantee data integrity. On other systems native file locks are mandatory, meaning that if one program locks a region of a file then other programs are actually prevented from accessing that region in a way that would violate the lock. On yet other systems, whether native file locks are advisory or mandatory is configurable on a per-file basis. To ensure consistent and correct behavior across platforms, it is strongly recommended that the locks provided by this API be used as if they were advisory locks.
[...]
However, as you can see the exact nature of the lock is platform-specific.