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I have googled bit , but dint find way to unload dll using JNA ,from java Class. And as i am using dll to transfer data from usb device using this dll, i have to unload my dll from java class in order to re-use my usb device with same class without closing my whole program. here is how i load my dll using JNA

public interface UsbSensor extends Library {

        UsbSensor INSTANCE = (UsbSensor) Native.loadLibrary(
                (Platform.isWindows() ? "D:\\UsbDevice.dll" : "D:\\UsbDevice.dll"), UsbSensor.class);

        int SearchDevices();

        Pointer Startacquisition(String type);
}

and by

 UsbSensor sdll = UsbSensor.INSTANCE;

Dll is loded. And here how i use my function 

sdll.SearchDevices();
sdll.Startacquisition();

And now after using these function I must have to unload my dll in again load dll using above code. order reuse these function.

So how to unload dll dynamically Using JNA?

Jony
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3 Answers3

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NativeLibrary.dispose() should do what you are looking for. NativeLibrary is a 1:1 representation of the native library you are using (and is used internally by Native.loadLibrary() anyway). So

  1. null the reference returned by Native.loadLibrary() and
  2. call NativeLibrary.dispose()
Lonzak
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1

I had the same issue but using Native.dispose() did not help. The solution to my problem was this question and answer. It basically sets instance of the native library to null and calls the garbage collector.

dARKpRINCE
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You can create a temporary class loader, use native functions, null the reference to the class loader and it will be eligible for GC together with classes / dlls it loaded

Evgeniy Dorofeev
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  • I tried as you said. i made a temporary class transferred my interface of loading dll.I also null the reference of this temporary class after my work gets finis. But still it dint unloaded the dll and i am still getting same problem as it was. – Jony Nov 15 '13 at 12:49
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    You need to use a temporary `ClassLoader` to load the interface in question, not a temporary `Class`. JNA also provides [`NativeLibrary.dispose()`](http://twall.github.io/jna/4.0/javadoc/com/sun/jna/NativeLibrary.html#dispose()), but `NativeLibrary` has different usage than the interface mapping. – technomage Nov 15 '13 at 15:20