snapscraft snap.yaml for java apps using swing ui on ubuntu

Question

I have a basic java app using java.awt Swing UI and I want to create a snap for it so when it's installed there is a launcher available and my UI Launches. I use gradle and the jar task to create a jar which works fine.

Naturally I have in a class that when called loads my app just fine:

    package com.foo
    class Bar() {
         static void main(String... args) { launchUI() }
    }

I created a snap folder at the root of the project and a snap.yaml where i followed the instructions on https://snapcraft.io/docs/java-applications so i have a snap yaml that produces a snap file which also installs fine:

name: deepthought
base: core18  
version: '0.0.7'
summary: ""
icon: gui/foo.png
description: |
 Computes the ultimate answer for life the universe and everything

grade: devel # must be 'stable' to release into candidate/stable channels
confinement: devmode # use 'strict' once you have the right plugs and slots

# This doesn't work
#apps:
#  htmldoc:
#    command: desktop-launch $SNAP/bin/foo.sh
##    desktop: share/applications/htmldoc.desktop
#    plugs: [home, network, x11]
parts:
  foopart:
    plugin: gradle
    source: https://github.com/bsautner/foo.git
    source-type: git
    gradle-options: []   # suppress running of tests and run the war task
    gradle-output-dir: build/libs

I've spent quite some time trying to figure out:

• If i create a shell script to run a java -jar foo.jar command it ends up in the /snap directory but it's not on the users path so they can't get to it
• I've tried creating launchers but always get an error that my launcher can't be found, if i put it in my root folder as /bin/launch.sh snap can't find it and if i put it in the snap/bin/ folder i also get errors to not put things in the snap folder
• When I do install my snap, i don't see where it puts my jar i want to execute, so i can't write a script that does that

I'd really appreciate if anyone can share a working snap.yaml for a java program with a launcher and if there is any mention of a path to something that you note where those files are in relation to the path of the /snap/snap.yaml file

Answer 1

ok figured it out - the docs don't say this but the files are relative to the root of the project so even though the yaml says this is the launch

apps:
  cmd3:
    command: usr/bin/foo.sh

foo.sh should be in the root of the project and the orginize section here moves it to the bin dir

  foo:
    plugin: gradle
    source-type: local
    source: .
    build-packages:
      - openjdk-11-jdk
    stage-packages:
      - openjdk-11-jdk
      - x11-utils
    organize:
      ${SNAPCRAFT_PART_BUILD}/jg-snap: usr/bin/foo.sh

The jar is in the /snap/foo/current/usr/jar directory