Comment by never_inline
Comment by never_inline 13 hours ago
1. The article seems kind-of shallow. I didn't see any concrete (qualitative or quantitative) remarks about the "fast" part. I don't doubt you have reasons to do this - but I expected some information on what component are you writing using Rust + JNI, and how it helped? Or is it just a demo?
At some point, repeated calls into the JNI are counter-productive to performance, since the JIT can not optimize them. Pinning affecting garbage collection is another potential drawback if any of your rust calls are long lived. If we don't measure and just conclude "we are fast because rust is faster than Java, and we took average of both speeds", it's a disservice.
2. Also, I see unsafe for each call? I'd rather isolate this into a class / different file, since in JNI only few types of calls are possible. (method returning one of the primtive types, an object or `void`). This is the approach I took in dart jnigen. (Though there, the call is Dart -> Java, not Java -> Native language).
unsafe {
env.call_method_unchecked(
java_logger,
logger_method,
ReturnType::Primitive(Primitive::Void),
&[JValue::from(format_msg(record)).as_jni()]
);
}
public CompletableFuture<Integer> add_one(int x) {
long futureId = native_add_one(x); // Call Rust
return AsyncRegistry.take(futureId); // Get CompletableFuture
}
This article summarizes our experience from a commercial project that runs on an in-vehicle Android system. In this project, we needed to invoke Rust code(DB) from Java(App), so we couldn't directly use the project’s source code for demonstration. Instead, we created a demo project: https://github.com/GreptimeTeam/rust-java-demo
1. I agree that using Rust doesn't necessarily mean faster performance; it simply gives you the opportunity to implement some compute-intensive modules in Rust, which is a possible approach.
2. This is a great suggestion, and we organized our project in the same way. You don’t need to use unsafe for every call. However, if you want to call JNI APIs from Rust, unsafe is required.
3. Sorry, some details were missing here. We use AsyncRegistry(Java) as an intermediary. Before initiating an async operation in Rust, we need to call Java code in advance to register a future and obtain a unique future ID. After the async execution completes, we retrieve the registered future by its ID, and then complete it or complete it exceptionally depending on the async result. You can refer to this code: https://github.com/GreptimeTeam/rust-java-demo/blob/90ffa0ba... and https://github.com/GreptimeTeam/rust-java-demo/blob/90ffa0ba...
4. This article was not generated by AI; it’s just that our official blog has a fixed template at the end. Sorry for the inconvenience.