Use Java Native Access to Determine Default Directory

Context and Problem Statement

JabRef needs to propose a file directory to a user for storing files. How to determine the “best” directory native for the OS the user runs.

Decision Drivers

  • Low maintenance effort
  • Follow JabRef’s architectural guidelines
  • No additional dependencies

Considered Options

Decision Outcome

Chosen option: “Java Native Access”, because comes out best (see below).

Pros and Cons of the Options

Use Swing’s FileChooser to Determine Default Directory

Swing’s FileChooser implemented a very decent directory determination algorithm. It thereby uses sun.awt.shell.ShellFolder.

  • Good, because provides best results on most platforms.
  • Good, because also supports localization of the folder name. E.g., ~/Dokumente in Germany.
  • Bad, because introduces a dependency on Swing and thereby contradicts the second decision driver.
  • Bad, because GraalVM’s support Swing is experimental.
  • Bad, because handles localization only on Windows.

Use user.home

There is System.getProperty("user.home");.

  • Bad, because “The concept of a HOME directory seems to be a bit vague when it comes to Windows”. See https://stackoverflow.com/a/586917/873282 for details.
  • Bad, because it does not include Documents: As of 2022, System.getProperty("user.home") returns c:\Users\USERNAME on Windows 10, whereas FileSystemView returns C:\Users\USERNAME\Documents, which is the “better” directory.

AppDirs

AppDirs is a small java library which provides a path to the platform dependent special folder/directory.

  • Good, because already used in JabRef.
  • Bad, because does not use Documents on Windows, but rather C:\Users\<Account>\AppData\<AppAuthor>\<AppName> as basis.

Java Native Access

  • Good, because no additional dependency required, as it is already loaded by AppDirs.
  • Good, because it is well maintained and widely used.
  • Good, because it provides direct access to Documents and other system variables.