Java - where to put application data?

Question

I'm writing a Java application which requires a number of resource files (there will be about 100 files of 20-40K each). They are not edited by the user, but will require periodic updates (the application will have a function to check for changes to the resource files and download them). Ideally, the application should be cross-platform.

Allowing write access to a subdirectory of the program directory is generally frowned upon. If I was doing it as a Windows application I might put them in Application Data, but that's not going to fly cross-platform. What would be the best place to put them?

Answer 1

I would typically create a directory (name starting with a period ".") in user's home directory (System.getProperty("user.home") if I am not mistaken) and use that for application specific storage. Alternatively, you could take the directory name from user at the time of application installation.

Answer 2

Have a directory you use to keep these files in. Put that information in a properties configuration file. When you start up load the configuration file from your application install directory. From that properties file it tells you where to find your file directory. When your installer runs it can write out this configuration file for the platform you are installing on, and that can be OS specific.

Answer 3

Provide a configurable location, but default to a directory in the user's home directory, or in an OS-specific location.

You'll have to deal with this in a platform-specific way no matter what. You have a few options under OS X, though. For unix-like systems either a home directory, or perhaps something under /var.

That said, I don't believe a program managing its own data in its own directory is a bad thing; consider a program with an embedded database or similar. It's much more reliable to use an app home directory.