io7m-com/jade

Java application directory etiquette

jade

JVM	Platform	Status
OpenJDK (Temurin) Current	Linux
OpenJDK (Temurin) LTS	Linux
OpenJDK (Temurin) Current	Windows
OpenJDK (Temurin) LTS	Windows

jade

The jade package provides an API for following good application directory etiquette.

Features

• API for handling application data directories.
• Implements the XDG Basedir specification on Unix-like platforms.
• Implements best-practice directory management on Windows platforms.
• Support for portable applications.
• High-coverage automated test suite.
• Written in pure Java 17.
• OSGi-ready.
• JPMS-ready.
• ISC license.

Usage

Modules

Applications use jade via the com.io7m.jade.api module, but should also have the com.io7m.jade.vanilla module on the class/module path. If the com.io7m.jade.vanilla module is not available, the jade package will unconditionally return paths equivalent those returned by portable mode.

Using Directories

The jade package selects a set of application paths based on the current operating system and the given configuration information. Getting access to the basic set of application directories for an application named Widget is straightforward:

final var configuration =
  ApplicationDirectoryConfiguration.builder()
    .setApplicationName("Widget")
    .build();

final var directories =
  ApplicationDirectories.get(configuration);

System.out.println("Configuration directory: " + directories.configurationDirectory());
System.out.println("Data directory: " + directories.dataDirectory());
System.out.println("Cache directory: " + directories.cacheDirectory());

Portable Mode

Applications, particularly on Windows, often want to run in portable mode. Portable mode essentially means that all of the paths used by the application are given relative to the initial working directory of the application. This is typically used to facilitate running applications from removable USB storage devices without saving any data to the host operating system storage.

The jade API allows for specifying the name of a system property that will be consulted in order to determine if the application wants to run in portable mode. If the named system property has a value parsed as true, the API will return paths relative to the application rather than system-specific paths.

final var configuration =
  ApplicationDirectoryConfiguration.builder()
    .setApplicationName("Widget")
    .setPortablePropertyName("com.io7m.example.portable")
    .build();

System.setProperty("com.io7m.example.portable", "true");

final var directories =
  ApplicationDirectories.get(configuration);

System.out.println("Configuration directory: " + directories.configurationDirectory());
System.out.println("Data directory: " + directories.dataDirectory());
System.out.println("Cache directory: " + directories.cacheDirectory());

Override

The jade API allows for specifying the name of a system property that will be consulted in order to determine if the application wants to override the directory used to calculate application directories. If the named system property exists, the value of the property will be treated as a path, and all application directories will be calculated relative to this path.

final var configuration =
  ApplicationDirectoryConfiguration.builder()
    .setApplicationName("Widget")
    .setOverridePropertyName("com.io7m.example.override")
    .build();

System.setProperty("com.io7m.example.override", "/tmp/x");

final var directories =
  ApplicationDirectories.get(configuration);

// Prints: /tmp/x/config
System.out.println("Configuration directory: " + directories.configurationDirectory());

// Prints: /tmp/x/data
System.out.println("Data directory: " + directories.dataDirectory());

// Prints: /tmp/x/cache
System.out.println("Cache directory: " + directories.cacheDirectory());