---
nav_order: 26
parent: Decision Records
---
# 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

* Use Swing's FileChooser to Determine Default Directory
* Use `user.home`
* [AppDirs](https://github.com/harawata/appdirs)
* [Java Native Access](https://github.com/java-native-access/jna)

## 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.