I can’t speak to the Rustler, but the JNI bindings for Rust are quite good. There are a lot of areas where you can still shoot yourself in the foot, lots of uns

I can’t speak to the Rustler, but the JNI bindings for Rust are quite good. There are a lot of areas where you can still shoot yourself in the foot, lots of unsafe. But there are patterns they encourage that are very safe, like associating lifetimes to Java objects that are instantiated in the Rust code appropriately. It also has good interfaces for working with arrays and avoid some of the foot guns in traditional C JNI libraries. It’s not quite possible to have no unsafe code in JNI with Rust (in my experience) but it is very easy to isolate to very small areas of your code.