JEP 343: Packaging Tool

OwnerKevin Rushforth
TypeFeature
ScopeJDK
StatusCandidate
Componentdeploy / packager
Discussioncore dash libs dash dev at openjdk dot java dot net
EffortM
DurationM
Relates toJEP 311: Java Packager API & CLI
Reviewed byAlexander Matveev, Alexey Semenyuk, Andy Herrick, Kevin Rushforth, William Harnois
Created2018/04/04 19:22
Updated2018/10/16 23:39
Issue8200758

Summary

Create a new tool for packaging self-contained Java applications.

Goals

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

Non-Goals

Motivation

Many Java applications need to be installed on a native platform 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 of that platform. For example, on Windows users expect to be able to double-click on an installer 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. Applications installed as service daemons, moreover, may require registering the service with the operating system.

There is also a need for a tool that can package the JDK itself for installation on a target system. Absent such a tool, JDK images are only published in the tar.gz zip formats.

A packaging tool can also help fill gaps left by other technologies such as Java Web Start, which was removed from Oracle’s JDK 11, and pack200, which was deprecated in JDK 11 for removal in a future release. 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 in connection with the removal of JavaFX.

Description

The jpackager tool will take as input a Java application and a Java run-time image, and produce a Java application image that includes all the necessary dependencies. It will also be able to produce a native package in a platform-specific format, such as an exe on Windows or a dmg on macOS. The tool will have options that allow packaged applications to be customized in various ways.

Features

The tool will provide the following features:

The following features will be included if there is time:

Running the tool

The input to jpackager includes: a Java run-time image, a Java application in one of several formats, and various command line options to control the generation of the final image or package.

The following types of applications are supported:

If no custom run-time image is provided then the tool will run jlink to create a JDK for the application.

The output of jpackager is a Java application image that includes all necessary Java dependencies. The image is stored in a single directory in the filesystem and can include the following:

As an example, the image format for a HelloWorld application might look like this:

HelloWorld/
    HelloWorld.exe     [this is the native launcher]
    app/
      [application resource, configuration, and support files go here]
    runtime/
      [custom Java runtime image goes here]

When the application is started, the launcher will read the configuration files and launch the embedded Java run-time image with the specified arguments.

The application image can be redistributed as-is, or it can be packaged as a native, installable package (for example, in msi or dmg format).

In this latter case, the tool can either create a native package from a previously created application image, or it can create a native package directly. The native package will include the following:

Delivering jpackager

The jpackager tool will be delivered as part of the JDK in a new jdk.packager module. This tool will be based on the javapackager tool, with all features related to Java Web Start and JavaFX removed. The command-line interface (CLI) will conform to JEP 293: Guidelines for JDK Command-Line Tool Options. In addition to the command-line interface, jpackager will be accessible via the ToolProvider API (java.util.spi.ToolProvider) under the name "jpackager".

Some features, such as the single-instance launcher, might require a run-time API that an application can call. If so, we will provide a run-time module with the necessary API.

Issues

We need to specify the layout of an application image and define what is supported versus unsupported, to make it clear for developers what they should or should not depend on, for example, the location of the application launcher, any user-editable configuration files, and so forth.

We should include some command-line examples and describe the content of the run-time image produced.

Testing

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

Dependencies

Native packages will be generated using tools on the target platform. For Windows, there are two additional tools that developers will need to install if they want to generate native packages:

There are efforts underway to enhance jlink to generate native launchers. Some level of coordination may be needed between jlink and jpackager.