Tutorial to create AppImage out of Java application

Creating AppImages
1

Hello,

I am the new maintainer of a Java open source software. Historically the software was distributed as .exe, .dmg, .rpm and .deb and as the new maintainer I would like to continue to support the 3 Os. At the moment I am managing the builds for .exe and .dmg but I don’t know how the .deb and .rpm were generated. I cam across AppImage and I think it may be the solution for me, but I could not find an in-depth tutorial, hence I have the following questions:
- can someone share ressources on how to build step by step an AppImage out of Jar application ?
- is is possible to build the flatpack from windows platform or will I need to use a virtual machine for this?

Thank you in advance for your help.

2

I don’t know about Flatpak (it is a different project) but it is easy to build an AppImage from a jar. Essentially you bundle JRE and the application into the AppImage.

I don’t know if it is possible using Windows (possibly it is but I don’t have a Windows machine), so I think the easiest solution for you is to use a service like Travis CI or GitLab CI that builds the AppImage in the cloud.

Here are some examples of yml recipes for Java applications:

https://github.com/AppImage/AppImages/search?q=jar+ingredients&unscoped_q=jar+ingredients

You run these using the pkg2appimage command on a Debian/Ubuntu machine.

I am the new maintainer of a Java open source software.

Can you point me to your software? If it is living on GitHub or GitLab, I may even be able to send you a pull request/merge request that would build the AppImage for you.

3

Hi,

If you’re using Eclipse, you might be interested in this plugin: https://gitlab.com/brotenet/ide.appimage.export

4

Thank you very much for proposing your help.

The project is hosted here: https://github.com/akasolace/HO (the GitHub project just has one commit because it was just moved out from SourceForge but in reality it is an old project)

I guess it will be easier for you if I upload a release, I can do that later today.

But what is really produce by the build system is:

  • a folder with external JARs (no JRE at the moment)
  • some resources, mostly gifs
  • a java class (the application updater), the application as a JAR
  • and a script Launcher (.bat or .sh)

the script basically launch first the updater and then the application.
Hence, the update part work as follow:

  1. from the app, user can check for new version and download update in practice a .update zip file
  2. at next start the updater unzip the file in the application repository

I am not sure whether or not an AppImage can manage the update part - fyi it also works like this for the dmg Image). But in case that part is not possible, I think it will be acceptable to ask Linux users to download new version instead of using the updating part.

Thank you in advance for your help.

5

Oracle is making it so hard to download JRE these days. Is there a way to get the latest one using wget?

6

I could not find a downloadable JRE link either.
I am also ready to build it using an Ubuntu or Debian VM. In that case, would that be possble to get the JRE from repository? Also, would that help if I first manage to create a .deb for my app?

8

Making a deb for your app is not needed. Finding a download link for JRE is. Possibly openjre packages from Ubuntu 14.04 can be used, but I have not tried that route so far.

9

https://github.com/probonopd/SystemImageKit/blob/master/boot/bin/generate-java-extension has:

URL=$(wget -qq "https://www.java.com/en/download/linux_manual.jsp" -O - | grep "Linux x64 en JRE" | head -n 1 | cut -d '"' -f 4 | xargs)
wget "$URL" -O - | tar xfvz -