The JNI is super useful, but sometimes it's kind of a pain to work with. Every time I work with it I find myself doing the same painful things I did the last time I worked with it.
For a long while I just lived with the Sisyphean absurdity, but it's time for that to stop.
So far this is just four bash scripts but with just those I feel less dread at the prospect of working with the JNI.
These scripts assume your classes live in ./target/classes, so if you're not
using maven you'll need to do a bit of wrangling (or submit a PR to generalize
:D ), but by the same token if you are using maven this should all work like
magic.
GNU Bash 4.0 or greater (for associative arrays and gnu find options)
A project with class files that live in target/classes (If you're using Maven
you're probably fine)
Since these are bash scripts you can just clone and run:
cd /some/directory/
git clone https://github.com/joshbooks/jniUtil.gitThe first script generates the JNI header files for your classes in a jni
directory located in ./ ie the place you run the script from.
So cd to your project directory (parent of target).
Assuming you're using maven and have run mvn package or another lifecycle
command that generates class files you would just run:
/some/directory/jniUtil/genJniHeaders.shif you ls -R ./jniyou should see a file structure that mirrors your class
structure filled up with JNI headers. So go ahead and write some .c files.
Once you've done that you'll probably want to get rid of some of the JNI
header files. Specifically the ones that aren't included in any .c files
(or .h files included by .c files).
To do that just cd back up to the project directory (parent of target and
jni) and run
/some/directory/jniUtil/pruneJniHeaders.shYou'll notice I specifically reference .c files. pruneJniHeaders.sh does
not recognize .rs, .cpp, .objc or any other type of source file currently. Once again if this doesn't work for your use case I welcome PRs to generalize.
You can make a shared library with jniMake.sh. To do that just run
/some/directory/jniUtil/jniMake.shand it will emit a shared library named jniUtilLib.solib containing all your
JNI code for you to include.
You might be thinking to yourself "Hey, why don't you make it easy to do all this within the maven lifecycle" well that's the plan, see the Plans For expansion section.
I'm currently working on a project
(JoshDB to be specific) that uses
the JNI, so as I do things with the JNI I'm going to try to write scripts that
automate those tasks so I never have to do them again. I think the next thing
I'm going to run into is building a JNI library from maven automagically
in the maven lifecycle and including jniUtilLib.solib in a .jar file
automagically. Be nice if I could insert code directly into pom.xml, but
producing the snippets that need to be inserted would a very good first step