gradlex

Proof of concept gradlew without JDK dependency.

Install

• Download from releases
• sh gradlex

Goals

• Download gradle
• Install gradle to .gradle-folder
• Execute gradle

Side goals

• Be small (smaller than gradle-wrapper.jar)
• Almost no dependencies
• Run on main OSes, distros and architectures
• Bundle JDK with Gradle, so no JDK is required at all

Assumptions

• User has sh installed
• User has an internet connection

Notes

• Shell can be of any kind (sh, bash, zsh, fish)
  • For windows this means MinGW (git bash), Cygwin, WSL, WSL2 or something similar

Rant

I've been in some discussion about this topic, where I came to suggest cosmopolitan.
This is a cool project, and it promises to do what is needed, except it does not support different architectures.
It says it does, but in reality it requires qemu to be installed.
My POC above does not require that, and should work on ARM as well as x86 as long as the os/distro/arch is targeted for build.
Note one difference is that my POC does not work on pure windows, a shell with sh is required. Not sure how to fix.
Had cosmopolitan proper ARM support it should be straight forward to convert.

After some discussions I realize that the current gradlew script-approach is fine, given the extent of sh being available.
The only problem is that sh can't download anything, if it could download something the rest would be possible.
This POC is basically that: Make sh able to download and execute something, on any system.

About distros

Need to build against several distros.
In reality only need glibc + musl + any other libc-thing.
For all I know building on alpine and debian should cover the most.
Reason for this is to make the executables smaller.
Statically built binary would not require a special distro, but could get up to as much as >700KB, while shared is 14KB. So two binaries per architecture doesn't matter much.

Weaknesses

• Very hacky
• Two-/multi-stage install
  • Note that if gradle had JDK bundled and was a single binary it would not need several stages
• Does not support https
  • Use hashing instead, because libcurl and/or openssl makes the binary much larger
  • Possible to re-write
  • Hashing should prevent tinkering of MITM, but peeking is still possible
• Does not support Windows double-click or CMD
• Scalability: With more OS/distro/arch support the binary will grow
  • At the same time, as some systems become obsolete they can be removed, and/or special versions can be built

Under the hood

How it actually works:

• Stage 1:
  • makeself archive containing:
    • Simple program written in C using shared libraries for socket downloads a second stage installed over HTTP ( not https)
    • Simple program built for multiple OS/distro/arch
    • Script executes every binary until one works
    • If one works stage 2 installer will be downloaded, else it quits
    • Stage 2 installer is executed
• Stage 2:
  • makeself archive containing:
    • gradle (extracted) + a script
    • Script simply copies gradle to .gradle