Java Native Access doesn’t do C++, right?

by

What this question amounts to is asking how to call C++ instance methods using JNA, and it’s possible, but you’re going to have to do some work. In particular, you’ll need to write a wrapper which extern "C"s any functions you actually need to invoke.

For any arbitrary type* function() definition you can map the method using JNA as returning a com.sun.jna.Pointer, but you won’t be able to invoke methods on a C++ object from JNA.

A simple workaround for this would be to write a C interface library that simply invokes the method on the objects for you…so if you have some member function foo() you could export a C method from your C++ code:

extern "C" void bar(type* var){
   var->foo();
}

Obviously this will add some work for you…but I suspect the overhead for switching to JNI would be about the same.

JNA only cares about the way in which the method is exported in the DLL — and that must be without C++ decorations (hence the extern "C"), so you can do whatever you need to within any such method without exposing methods that you call.

In my contrived example above, this means that foo(), as long as it is defined within the DLL does not in fact have to even be exposed. Since it’s a C++ function, JNA cannot call it directly, but it can be called from within a function that JNA can call, which is why my proposed solution works.

So, yes, you can fully encapsulate calls to all the member functions (create, operate, destroy) in a single function and JNA won’t care.

More Related Contents:

  1. Use JNI instead of JNA to call native code?
  2. What is the native keyword in Java for?
  3. Where to find source code for java.lang native methods? [closed]
  4. Adding new paths for native libraries at runtime in Java
  5. Getting active window information in Java
  6. Failed to load the JNI shared Library (JDK)
  7. How can I tell if I’m running in 64-bit JVM or 32-bit JVM (from within a program)?
  8. How to import a class from default package
  9. How to fix an UnsatisfiedLinkError (Can’t find dependent libraries) in a JNI project
  10. How to bundle a native library and a JNI library inside a JAR?
  11. What makes JNI calls slow?
  12. How to obtain JNI interface pointer (JNIEnv *) for asynchronous calls
  13. Calling Win32 API method from Java
  14. Managing DLL dependencies with Maven
  15. How to pass C structs back and forth to Java code in JNI?
  16. Why is System.arraycopy native in Java?
  17. In Java Swing how do you get a Win32 window handle (hwnd) reference to a window?
  18. java.lang.UnsatisfiedLinkError: Native Library XXX.so already loaded in another classloader
  19. Eclipse reported “Failed to load JNI shared library” [duplicate]
  20. passing string array from java to C with JNI
  21. how to make jni.h be found?
  22. JNI Hello World Unsatisfied Link Error
  23. how to set java library path for processing
  24. JNI – How to callback from C++ or C to Java?
  25. JNI Calls different in C vs C++?
  26. jni.h: no such file or directory
  27. Is it possible to use sun.misc.Unsafe to call C functions without JNI?
  28. Linking static library with JNI
  29. Unable to install rJava in R 3.0 in Ubuntu 13.04
  30. Is it possible to find the source for a Java native method?

Leave a Comment