Java HotSpot Virtual Machine

Ok, I have been working on this for quite some time now and I simply can not figure it out. So any ideas are more than welcome. :)

I have Java code that uses a DLL that I created in C++. My C++ code links with a library made by a 3rd party (don't have access to the source or anything). The 3rd party's code creates a new thread and calls a callback function that I define in my C++ code. This callback is called continuously until I perform some other code to stop it. Now for the tricky part. In my callback function I need to pass some data back in Java. Here is where my design falls apart. Since the callback function is technically part of the 3rd party's thread, I have to call AttachCurrentThread() in the callback to get the JNIEnv pointer in order to ultimately call my desired Java method. The problem is that my Java method (or even the C++ callback function) are only invoked if I do a sleep() in my C++ code after I start the 3rd party code which creates the thread. If I do a Thread.sleep() in Java after I call the native function code, it just sleeps and the callbacks never get called. It appears as though the thread dies as soon as I return from my C++ code.

So now I am stuck. I have tried creating a thread in Java which simply calls the C++ code and the C++ code just loops waiting for an updated flag, however, this causes the 3rd party's thread creation code to fail (not quite sure why). However, even if their code worked, I'm not convinced this is even proper design. I apologize if this is simply a threading design principle as my multithreading programming techniques are a bit rusty and I've never done a multithreaded application this complex (this is a simplified version, but the idea is the same).

I welcome any suggestions or even documentation that may lead me in the right direction. Thanks in advance.