Native methods inside C++ class

Question

Hey all,
Tried posting this already but it didn't appear in the forums. So apologies if this appears twice on same forum :o)
Want to wrap my native methods inside a C++ class but get UnsatisfiedLinkerError when I do. Is it possible to do this? Do I have to change some method signatures or what?
I want something like :
public class A
native void doSomething();
class B
public:
JNIEXPORT void JNI Java_A_doSomething() { ... } /* or whatever */
It works ok outside of a C++ class but I'd prefer to contain my methods inside a class. Any help?
Cheers,
Conor

Answer 1

Java needs to find your functions in the DLL or SO. But the names are "mangled" if you declare the function inside a class - even declaring the function "static" does not help. For instance, using the Microsoft C++ compiler:
class B
public:
static JNIEXPORT void JNI Java_A_doSomething() { ... }
};the name is mangled to ?Java_A_doSomething@B@@SAXXZ
But Java tries to locate the entry _Java_A_doSomething@0 in the DLL.
You can write the global functions as:
JNIEXPORT void JNI Java_A_doSomething() {
    B::doSomething();
}and implement your functions in the class B. The advantage of this approach is that you can write all bookkeeping work of converting Java data to C++ data in the global function, and leave the real work to the function declared in the C++ class.