Best practice from Rust's HashMap to Java Map?

[tisonkun]

A java.util.HashMap should be fine. But currently it's a bit complicated to wrap a utility for doing so, compared with env.new_string for converting strings.

[tisonkun]

I wrote a utility for OpenDAL's usage:

apache/opendal#3069

fn hashmap_to_jmap<'a>(env: &mut JNIEnv<'a>, map: &HashMap<String, String>) -> Result<JObject<'a>> {
    let map_object = env.new_object("java/util/HashMap", "()V", &[])?;
    let jmap = env.get_map(&map_object)?;
    for (k, v) in map {
        let key = env.new_string(k)?;
        let value = env.new_string(v)?;
        jmap.put(env, &key, &value)?;
    }
    Ok(map_object)
}

[argv-minus-one]

JNIEnv::new_string is a wrapper around a C JNI function; it's built into the JVM.

Converting between Java and Rust types in general is another story altogether. The way you've done it pretty much is the best practice at this point. Perhaps someone will write some conversion traits and/or a JNI binding generator in the future, but that would be a lot of work.

[tisonkun]

Make sense.