On 04.06.2015 17:10, Atri Sharma wrote: > Something like a smart pointer might be useful here. > > I thing that I also feel that the memory handling of the C++ objects might > be the biggest issue here. What I think can happen is having Java objects > *own* C++ objects and clean up in finalize() methods. Only a small idea > though...
>From my experience, finalize() happens far too late to be useful. There's a very fundamental impedance mismatch between Java and C++: C++ has destructors, Java doesn't; and finalize() is not a good replacement for a destructor because it doesn't know squat about scope. For callbacks, it's probably best to just transfer ownership of objects from Java to C++: that would imply creating the object in the JNI layer, then sending an std::auto_ptr (or std::unique_ptr in C++11) to the callback handler. Once it owns the object the C++ app can do whatever it wants with it. If that's not possible, the second option is to use proxy objects instead of real value objects in the callbacks. Proxy objects are C++ objects that contain a global reference to a Java object and whose native methods are just wrappers to JNIEnv::Call*Method. The constructor and assignment operators would always create new global references and the destructor would release the global reference and you'd have almost Java-like garbage collection semantics. -- Brane > On Thu, Jun 4, 2015 at 8:23 PM, Branko Čibej <[email protected]> wrote: > >> On 04.06.2015 15:45, Vladimir Ozerov wrote: >>> Igniters, >>> >>> Lots of our features rely on callbacks from Ignite to user code. This is >>> essential for task execution, cache invokes, cache store, continuous >>> queries, messaging, etc.. >>> >>> Ideally from user perspective target class should look somewhat like >> this: >>> class MyListener : public IListener<MyKey*, MyVal*> { >>> public: >>> bool Invoke(MyKey*, MyType*); >>> } >> Please please please do not use raw pointers in the public API. This is >> a memory management nightmare waiting to happen. Either use const >> references or shared pointers. std::auto_ptr_ref is an option, but not a >> very good one. >> >> -- Brane >> >> >
