This is perhaps similar to previous posts, but I want to be specific about the use of locking on a network, rather than locally. I want to write a file to a shared location, so it may well go on a network (certainly a Windows network, maybe Mac). I want to prevent other people from reading any part of this file whilst it it being written. This will not be a highly concurrent process, and the files will be typically less than 10MB.
I’ve read the FileLock documentation and File documentation and am left somewhat confused, as to what is safe and what is not. I want to lock the entire file, rather than portions of it.
Can I use FileChannel.tryLock(), and it is safe on a network, or does it depend on the type of network? Will it work on a standard Windows network (if there is such a thing).
If this does not work, is the best thing to create a zero byte file or directory as a lock file, and then write out the main file. Why does that File.createNewFile() documentation say don’t use this for file locking? I appreciate this is subject to race conditions, and is not ideal.
This can’t be reliably done on a network file system. As long as your application is the only application that accesses the file, it’s best to implement some kind of cooperative locking process (perhaps writing a lock file to the network filesystem when you open the file). The reason that is not recommended, however, is that if your process crashes or the network goes down or any other number of issues happen, your application gets into a nasty, dirty state.