Question: How I use `GetObjectRefType` about jni-rs HOT 4 CLOSED

This crate doesn't have any wrapper for GetObjectRefType because it uses Rust's type and lifetime system to keep track of JNI object reference types at compile time.

• An owned JByteBuffer, JClass, JObject, JObjectArray, JPrimitiveArray, JString, or JThrowable is always a JNI local reference.
• An AutoLocal owns a JNI local reference (one of the types above) and deletes it when dropped.
• A GlobalRef or WeakRef is always a JNI global or weak reference, respectively.
• There are no invalid references. The local reference types listed above all have a Rust lifetime parameter that proves that they're still valid. GlobalRef and WeakRef are valid until they are dropped.
• AutoElements, AutoElementsCritical, JList, JListIter, JMap and JMapIter all borrow a JNI reference (not necessarily local).

Hence, the pattern you've been using in C++ shouldn't be necessary when using this crate.

I can think of one exception, though: if you receive a raw JNI object reference (that is, not one wrapped by one of the types in jni::objects) from some other code and don't know whether it's local or global. Is that your situation?

from jni-rs.

Yes.

Also, there is still invalid references. An invalid reference can be created with

#[test]
fn get_local_ref_type() {
    let env = attach_current_thread();
    // let obj = env.new_string("test").unwrap();
    let obj = JObject::null();

    let auto_ref = AutoLocal::new(obj, &env);
    // left: `InvalidRefType`
    assert_eq!(env.get_object_ref_type(&auto_ref).unwrap(), RefType::LocalRefType);
}

from jni-rs.

It looks like jni-rs is currently missing null checks before calling delete_local_ref and delete_global_ref (the spec doesn't seem to clarify if it's OK to pass null to these, though I guess they are just noops as you'd want).

Null is a special case though, and I think it's probably good that you can make a null GlobalRef or null AutoLocal.

You shouldn't have to worry about whether references are valid or not unless dealing with raw sys types with unsafe code.

from jni-rs.

Oh okay, thanks.

from jni-rs.