Add a Java system dependency for facilitating JNI development

I am working on Java bindings for a project. Java installations typically come with an include folder that has various headers for interacting with the JVM or the JNI. The include directory isn’t symlinked into a default header location by default, no does it typically reside in the same location across systems (Fedora, Ubuntu, Windows, Mac, etc.).

I want to propose a Java system dependency that hooks up any libraries and include directories to your project.

I am interested in creating a PR for this myself.

[dcbaker]

Here’s my attempt to add some docs on writing system dependencies: https://github.com/mesonbuild/meson/pull/8228

[jpakkane]

As a dependency name jni is probably better than java. I looked into adding this ages ago but the need for it evaporated. From what I can remember it would have needed to do something like this (on Linux):

• detect currently used JVM
• trawl the file system for headers and libs (which are not under /usr/include but somewhere else, maybe under lib or share and, if memory serves, that path is different on Debian vs Fedora
• build up the corresponding compile and link args

Another thing I remember pondering was that there are two different ways of doing JNI, one required compiling the source with javah or something while the newer one worked in some easier way. It would be nice to not have to support the former but I don’t know how widespread its usage is nowadays.