JEP 392: Packaging Tool

Summary

Provide the jpackage tool, for packaging self-contained Java applications.

History

The jpackage tool was introduced as an incubating tool in JDK 14 by JEP 343. It remained an incubating tool in JDK 15, to allow time for additional feedback. It is now ready to be promoted from incubation to a production-ready feature. As a consequence of this transition, the name of the jpackage module will change from jdk.incubator.jpackage to jdk.jpackage.

The only substantive change relative to JEP 343 is that we replaced the --bind-services option with the more general --jlink-options option, described below.

Goals

Create a packaging tool, based on the legacy JavaFX javapackager tool, that:

• Supports native packaging formats to give end users a natural installation experience. These formats include msi and exe on Windows, pkg and dmg on macOS, and deb and rpm on Linux.

• Allows launch-time parameters to be specified at packaging time.

• Can be invoked directly, from the command line, or programmatically, via the ToolProvider API.

Non-Goals

• The following features of the legacy javapackager tool are not supported:

  • Java Web Start application support,
  • JavaFX-specific features,
  • jdeps usage for determining required modules, and
  • the Ant plugin.

• There is no GUI for the tool; a command-line interface (CLI) is sufficient.

• There is no support for cross compilation. For example, in order to create Windows packages one must run the tool on Windows. The packaging tool will depend upon platform-specific tools.

• There is no special support for legal files beyond what is already provided in JMOD files. There will be no aggregation of individual license files.

• There is no native splash screen support.

• There is no auto-update mechanism.

Motivation

Many Java applications need to be installed on native platforms in a first-class way, rather than simply being placed on the class path or the module path. It is not sufficient for the application developer to deliver a simple JAR file; they must deliver an installable package suitable for the native platform. This allows Java applications to be distributed, installed, and uninstalled in a manner that is familiar to users. For example, on Windows users expect to be able to double-click on a package to install their software, and then use the control panel to remove the software; on macOS, users expect to be able to double-click on a DMG file and drag their application to the Application folder.

The jpackage tool can also help fill gaps left by past technologies such as Java Web Start, which was removed from Oracle's JDK 11, and pack200, which was removed in JDK 14 (JEP 367). Developers can use jlink to strip the JDK down to the minimal set of modules that are needed, and then use the packaging tool to produce a compressed, installable image that can be deployed to target machines.

To address these requirements previously, a packaging tool called javapackager was distributed with Oracle's JDK 8. However, it was removed from Oracle's JDK 11 as part of the removal of JavaFX.

Description

The jpackage tool packages a Java application into a platform-specific package that includes all of the necessary dependencies. The application may be provided as a collection of ordinary JAR files or as a collection of modules. The supported platform-specific package formats are:

• Linux: deb and rpm
• macOS: pkg and dmg
• Windows: msi and exe

By default, jpackage produces a package in the format most appropriate for the system on which it is run.

Basic usage: Non-modular applications

Suppose you have an application composed of JAR files, all in a directory named lib, and that lib/main.jar contains the main class. Then the command

$ jpackage --name myapp --input lib --main-jar main.jar

will package the application in the local system's default format, leaving the resulting package file in the current directory. If the MANIFEST.MF file in main.jar does not have a Main-Class attribute then you must specify the main class explicitly:

$ jpackage --name myapp --input lib --main-jar main.jar \
  --main-class myapp.Main

The name of the package will be myapp, though the name of the package file itself will be longer, and end with the package type (e.g., myapp.exe). The package will include a launcher for the application, also called myapp. To start the application, the launcher will place every JAR file that was copied from the input directory on the class path of the JVM.

If you wish to produce a package in a format other than the default, then use the --type option. For example, to produce a pkg file rather than dmg file on macOS:

$ jpackage --name myapp --input lib --main-jar main.jar --type pkg

Basic usage: Modular applications

If you have a modular application, composed of modular JAR files and/or JMOD files in a lib directory, with the main class in the module myapp, then the command

$ jpackage --name myapp --module-path lib -m myapp

will package it. If the myapp module does not identify its main class then, again, you must specify that explicitly:

$ jpackage --name myapp --module-path lib -m myapp/myapp.Main

(When creating a modular JAR or a JMOD file you can specify the main class with the --main-class option to the jar and jmod tools.)

Package metadata

The jpackage tool allows you to specify various kinds of platform independent metadata such as name and app-version, as well as platform-specific metadata for each platform.

The description of all jpackage options can be found in the jpackage man page.

File associations

You can define one or more file-type associations for your application via the --file-associations option, which can be used more than once. The argument to this option is a properties file with values for one or more of the following keys:

• extension specifies the extension of files to be associated with the application,
• mime-type specifies the MIME type of files to be associated with the application,
• icon specifies an icon, within the application image, for use with this association, and
• description specifies a short description of the association.

Launchers

By default, the jpackage tool creates a simple native launcher for your application. You can customize the default launcher via the following options:

• --arguments <string> — Command-line arguments to pass to the main class if no command line arguments are given to the launcher (this option can be used multiple times)
• --java-options <string> — Options to pass to the JVM (this option can be used multiple times)

If your application requires additional launchers then you can add them via the --add-launcher option:

• --add-launcher <launcher-name>=<file>

The named <file> should be a properties file with values for one or more of the keys app-version icon arguments java-options main-class main-jar module, or win-console. The values of these keys will be interpreted as arguments to the options of the same name, but with respect to the launcher being created rather than the default launcher. The --add-launcher option can be used multiple times.

Application images

The jpackage tool constructs an application image as input to the platform-specific packaging tool that it invokes in its final step. Normally this image is a temporary artifact, but sometimes you need to customize it before packaging it. You can, therefore, run the jpackage tool in two steps. First, create the initial application image with the special package type app-image:

$ jpackage --name myapp --module-path lib -m myapp --type app-image

This will produce an application image in the myapp directory. Customize that image as needed, and then create the final package via the --app-image option:

$ jpackage --name myapp --app-image myapp

Runtime images

An application image contains both the files comprising your application as well as the JDK runtime image that will run your application. By default, the jpackage tool invokes the the jlink tool to create the runtime image. The content of the image depends upon the type of the application:

• For a non-modular application composed of JAR files, the runtime image contains the same set of JDK modules that is provided to class-path applications in the unnamed module by the regular java launcher.

• For a modular application composed of modular JAR files and/or JMOD files, the runtime image contains the application's main module and the transitive closure of all of its dependencies.

The default set of jlink options used by jpackage is

--strip-native-commands --strip-debug --no-man-pages --no-header-files

but this can be changed via the --jlink-options option. The resulting image will not include all available service providers; if you want those to be bound then use --jlink-options and include --bind-services in the list of jlink options.

In either case, if you want additional modules to be included to the runtime image you can use the jpackage tool's --add-modules option. The list of modules in a runtime image is available in the image's release file.

Runtime images created by the jpackage tool do not contain a src.zip file.

If you wish to customize the runtime image further then you can invoke jlink yourself and pass the resulting image to the jpackage tool via the --runtime-image option. For example, if you've used the jdeps tool to determine that your non-modular application only needs the java.base and java.sql modules, you could reduce the size of your package significantly:

$ jlink --add-modules java.base,java.sql --output myjre
$ jpackage --name myapp --input lib --main-jar main.jar --runtime-image myjre

Application-image layout and content

The layout and content of application images are platform-specific. Actual images contain some files not show in the layouts below; such files are implementation details that are subject to change at any time.

Linux

myapp/
  bin/              // Application launcher(s)
    myapp
  lib/
    app/
      myapp.cfg     // Configuration info, created by jpackage
      myapp.jar     // JAR files, copied from the --input directory
      mylib.jar
      ...
    runtime/        // JDK runtime image

The default installation directory on Linux is /opt. This can be overridden via the --install-dir option.

macOS

MyApp.app/
  Contents/
    Info.plist
    MacOS/          // Application launcher(s)
      MyApp
    Resources/      // Icons, etc.
    app/
      MyApp.cfg     // Configuration info, created by jpackage
      myapp.jar     // JAR files, copied from the --input directory
      mylib.jar
      ...
    runtime/        // JDK runtime image

The default installation directory on macOS is /Applications. This can be overridden via the --install-dir option.

Windows

MyApp/
  MyApp.exe         // Application launcher(s)
  app/
    MyApp.cfg       // Configuration info, created by jpackage
    myapp.jar       // JAR files, copied from the --input directory
    mylib.jar
    ...
  runtime/          // JDK runtime image

The default installation directory on Windows is C:\Program Files\. This can be overridden via the --install-dir option.

Delivering jpackage

The jpackage tool is delivered in the JDK in a module named jdk.jpackage.

The command-line interface conforms to JEP 293 (Guidelines for JDK Command-Line Tool Options).

In addition to the command-line interface, jpackage is accessible via the ToolProvider API (java.util.spi.ToolProvider) under the name "jpackage".

Testing

Most tests can be done with automated scripts, but there are a few considerations to be aware of:

• Testing native packages may require optional tools to be installed; those tests will need to be written such that they are skipped on systems without the necessary tools.

• Verifying some types of native packages (e.g., exe on Windows or dmg on macOS) may require some manual testing.

• We need to ensure that native packages can be installed and uninstalled cleanly, so that developers can test in their local environment without fear of polluting their systems.

Dependencies

Native packages are generated using tools available on the host platform. On Windows, developers must install the third-party “Wix” tool in order to generate msi or exe packages.