Unable to load dll with JNI outside of Nebeans IDE on XP

Question

I have a Netbeans Platform application with a module with a topComponent that loads a dll using Java Native Interface. The dll was created in Visual Studio 2012 with the v110_xp toolset to communicate with a USB device. It does use some MFC functions and MFC is compiled as a static library from visual studio.

There are no problems with this application or dll when running on a Windows 7 32/64 bit computer. The dll and topComponent do not load at all on Windows XP computers.

To test the problem further I installed Netbeans 7.4 on the XP computer and attempted to load the dll while debugging. No problems found, all USB functions working, topComponent loads with no issues. If I release the program from here by packaging as a ZIP distribution the program does not load the DLL or the topComponent. It only works on the XP 32 bit computer if I run it from inside the Netbeans IDE.

I ran dependencyWalker on the dll file and the only missing dependencies are IESHIMS.dll and WER.dll, from what I've seen these are delay-loaded dll's and should never be needed in my application.

Does anybody have any clue on why this isn't working?

-------------------------Update-------------------------

I've updated the way that I load the dll inside of netbeans:

static{
        File dllPath = org.openide.modules.InstalledFileLocator.getDefault().locate("modules/lib/x86", "com.module.foo", false);
        try {
             System.setProperty("java.library.path", dllPath.getAbsolutePath());
             System.setProperty("jna.library.path", dllPath.getAbsolutePath());
             System.setProperty("jni.library.path", dllPath.getAbsolutePath());
             Field fieldSysPath = ClassLoader.class.getDeclaredField("sys_paths");
             fieldSysPath.setAccessible(true);
             fieldSysPath.set(null, null);
        } catch (Exception e) {
             throw new RuntimeException(e);
        }
    }

Then I load the dll as such:

DllInterface INSTANCE = (DllInterface) Native.loadLibrary(
             "My32bitdll" , 
            DllInterface.class);

This works great, again, only inside of the Netbeans IDE.... is there something I'm missing???

-------------------------Update 2-------------------------

I'm now also able to get this working inside of the Netbeans IDE by simply using

System.loadLibrary("My32bitdll");

It also works with no issues on 64 bit machines. I got this working by fixing the method names in my dll file with javah.

Again, I'm using the x86 JDK, x86 JRE, and with a 32bit dll... still doesn't work outside of netbeans.

-------------------------Update 3-------------------------

I've narrowed this down to a problem with Netbeans Platform Applications. I have no trouble loading the dll from a standard java application using

System.load("myDllPath");

I've followed this guide: NetBeans Development 7 - Windows 7 64-bit … JNI native calls ... a how to guide which describes loading a dll within a Netbeans module but I still can't get this working on a 32 bit system outside of Netbeans IDE.

Answer 1

I found a solution to the problem. Still might need to be something that needs to be addressed within the netbeans development crew, or I'm just missing something.

I was able to get my dll (in /release/modules/lib) with dependencies on winUSB.dll in the system32 folder working with JNA if I created a new netbeans platform application on the 32 bit computer from scratch.

Any Netbeans Platform Project that I start from the 64 bit computer and then transfer to a 32 bit computer will not load the dll dependencies correctly. You can debug them on the 32 bit computer but it will never work outside of the Netbeans IDE (7.4).

Answer 2

It is hard to tell exactly what is going on without at least an error message to go on. Assuming you don't have an minimum API version issue in your DLL, my educated guess is that you A) forgot to set the java.library.path, and B) will need additional copies of your binary because you cannot use the same dll on 32 and 64 bit machines. Under some circumstances, you may need to work very hard to avoid a third dll for 32 bit Vm's running on 64 bit machines (aka WoW64).

I would start by figuring out exactly what netbeans is packaging for you when you package "as a ZIP distribution." Your DLL file needs to be included somewhere and you must specify its location using -Djava.library.path= when you launch the application. See this related post about loading libraries for more information about how to point java to your native library. This path will be what you change to load 32/64 bit dlls or even dylibs for OS X and shared objects for the unixes. You should also seriously consider a more reliable (IDE independent) method of building and packing your library to avoid these interesting problems.