java - Safe to store pointer in JNI direct bytebuffer? -

i want create java object wrapper around native c++ object. putting pointer c++ object in direct bytebuffer so:

java side:

public class world {   private final bytebuffer pointer;   public world() {     pointer = init();   }    private native bytebuffer init();   public native void destroy(); } 

native side:

extern "c" jobject java_blabla_world_init(jnienv *e, jobject self) {   return env->newdirectbytebuffer(new world, sizeof(world)); } 

is safe? meaning, java funny things pointer, maybe relocating or garbage-collecting it?

secondly, if not know size of world in advance (it forward-declared), ok give 0 buffer size? (provided, of course, not try read buffer)

the jvm free manage bytebuffer object contain same address , capacity. won't memory pointed bytebuffer unless call bytebuffer methods on , never move it.

but since aren't going call bytebuffer methods, bytebuffer , jlong equivalent. seems me using jlong instead make clearer, if have cast on in jni function. after all, java side, creating , storing handle, , jni side, treating handle pointer. cast makes clear.