pass rust function as implementation for Java object about jni-rs HOT 5 OPEN

fn native_apply(mut env: JNIEnv, _class: JClass, input: JString) -> jstring {
    // Convert the Java input string to a Rust string
    let input_str: String = env.get_string(&input).expect("Invalid string").into();

    // Perform your processing on the input here.
    // For example, you can create a result string.
    let result_str = format!("Hello, {}", input_str);

    // Convert the result string back to a Java string
    let result_jstring = env
        .new_string(result_str)
        .expect("Couldn't create Java string");
    **result_jstring
}

fn main() {
...
    let method = NativeMethod {
        name: "apply".into(),
        sig: "(Ljava/lang/String;)Ljava/lang/String;".into(),
        fn_ptr: native_apply as *mut std::ffi::c_void,
    };
    let router_handler_native_class = env.find_class("shared/server/RouteHandlerNative").unwrap();
    let _ = env.register_native_methods(&router_handler_native_class, &[method]);
    let router_handler_ctor = env
        .get_method_id(
            &router_handler_native_class,
            "<init>",
            "(Ljava/lang/String;)V",
        )
        .unwrap();

    let router_handler = unsafe {
        env.new_object_unchecked(
            &router_handler_native_class,
            router_handler_ctor,
            &[JValue::Object(&j_string_path).as_jni()],
        )
    }
    .unwrap();

    let _ = unsafe {
        env.call_static_method_unchecked(
            &server_class,
            add_route_method_id,
            ReturnType::Primitive(Primitive::Void),
            &[JValue::Object(&router_handler).as_jni()],
        )
    }
    .unwrap()
    .v()
    .unwrap();

...
}