29 releases (10 breaking)
0.11.2 | Jul 31, 2023 |
---|---|
0.10.2 | Jul 27, 2023 |
#10 in #objects
211 downloads per month
45KB
1K
SLoC
jnat
A wrapper around the jni crate
View the documentation
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::{
jnat_macros::jnat,
jni::{objects::JClass, JNIEnv}, // jni crate, re-exported by jnat
Class,
Env,
Signature,
Type,
};
jnat!(HelloWorld, caller, (JNIEnv, JClass) -> ());
fn caller(env: JNIEnv, class: JClass) {
let mut env = Env::new(&env);
let class = Class::new(&mut env, class);
class
.call_static_method("hello", Signature::new(&[], 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.
Notes
- Jnat re-exports jni by default. If you want to use a different version of jni, you can disable either the default features or the
jni
feature. - Jnat exports a macro,
jnat::jnat_macros::jnat
(seen in the example above), which is used to generate theJava_HelloWorld_caller
function. This macro can be disabled by disabling either the default features or thejni-macros
feature. Note that the macro keeps the original function to prevent unintuitive behavior (so you can, in your Rust code, call justexample()
instead ofJava_org_example_Class_example()
while still allowing Java to call it).
Dependencies
~1–12MB
~83K SLoC