在资源（类路径）文件夹和数据库上。

Question

I'm wondering if it is ok to use your resource folder as a database folder. I have a an application that run a small semantic database. Most of the work is done in memory but from time to time i need to commit the data in the database. It also saves the data, for when the program will be restarted again. I'm asking this because it sounds weird to me to have a growing Jar/bundle. Indeed, by default sbt or maven, put your resources in your jar/bundle.

Can someone enlighten me a bit about how to properly use the resources folder. Shall it be read only ?

Answer 1

AFAIK you can't overwrite files that are in .jar from code. But you could create a file in same location to save any data (and use default data if file does not exist).

Answer 2

Resources should be considered read-only, as the entire application could reside in a .jar. Also some resources are cached.

However you may use a database as resource for an initial database template. This you can copy to a subdirectory of the user's home, which also makes this application multi-user / multi-tenant.

InputStream dbIn = SomeClassInJar.class.getResourceAsStream("/data/initial.hdb");
Path dbPath = Paths.get(System.getProperty("user.home"), ".myapp", "db.hdb");
Files.createDirectories(dbPath.getParent()); // .myapp
Files.copy(dbIn, dbPath, StandardCopyAction.REPLACE_EXISTING);

The REPLACE_EXISTING maybe not to use.