jnat

A wrapper around the jni crate

Example

Create a new Cargo lib project with cargo new --lib mylib and add the following to Cargo.toml:

[dependencies]
jnat = [latest version]

[lib]
crate-type = ["cdylib"]

Add the following to src/lib.rs:

use jnat::{
  env::{Class, Env},
  jni::{objects::JClass, JNIEnv}, // jni crate, re-exported by jnat
  signature::{Signature, Type},
};

#[no_mangle]
pub extern "system" fn Java_HelloWorld_caller(env: JNIEnv, class: JClass) {
  let mut env = env;
  let mut env = Env::new(&mut env);
  let mut class = Class::new(&mut env, class);

  class
    .call_static_method("hello", Signature::new(vec![], Type::Void), &[])
    .unwrap();
}

Then, run cargo build. Create a new file called HelloWorld.java and add the following:

public class HelloWorld {
  private static native void caller();

  static {
    System.loadLibrary("mylib");
  }

  public static void main(String[] args) {
    HelloWorld.caller();
  }

  public static void hello() {
    System.out.println("Hello, world!");
  }
}

Compile the java file with javac -h . HelloWorld.java. Then, run java -Djava.library.path=path/to/target/debug HelloWorld. You should see Hello, world! printed to the console.