[LWJGL] Library.loadNative does not work, System.load does for custom lib

Newbie & Debugging Questions
#1

Good day everyone,

I have a small project which uses jni and till now I had the dynamic library in an fixed folder for testing.
Now I am trying to bundle it within the jar and because I am using Lwjgl anyway for convenience I wanted to use the loading facilities from org.lwjgl.system.Library.

This does not work for me I received an java.lang.UnsatisfiedLinkError: test.Test.add(II)I Exception.
Lwjgl3 provides the following log for a lib not packed (And a similar for one with a packed lib):

[LWJGL] Version: 3.1.6 build 14
[LWJGL] 	 OS: Windows 10 v10.0
[LWJGL] 	JRE: 10.0.1 amd64
[LWJGL] 	JVM: Java HotSpot(TM) 64-Bit Server VM v10.0.1+10 by "Oracle Corporation"
[LWJGL] Loading library (system): lwjgl
[LWJGL] 	Found at: C:\Users\CJG\AppData\Local\Temp\lwjglCJG\3.1.6-build-14\lwjgl.dll
[LWJGL] 	Loaded from org.lwjgl.librarypath: C:\Users\CJG\AppData\Local\Temp\lwjglCJG\3.1.6-build-14\lwjgl.dll
[LWJGL] Loading library: C:\Users\CJG\eclipse-workspace\test\build\lib\main\release\test.dll
[LWJGL] MemoryUtil accessor: MemoryAccessorUnsafe
[LWJGL] 	Success

When I use System#load or System#loadLibrary (Even when using an absolute path to the file lwjgl3 extracted) everything works as expected.

When I use System#load after calling Library#loadNative the Exception stays the same.

Do I have some misconception about Library? Anyway, thanks to everyone who can help me (or can not help me but took the time to consider if he possibly could :wink: )

Have a nice weekend
-ClaasJG

#2

org.lwjgl.system.Library.loadNative() is not meant to load JNI libraries that the JVM can then resolve native methods from.
Instead, org.lwjgl.system.Library is meant to load the raw shared library using OS-specific API calls which the JVM does not know anything about in order to manually resolve function pointer addresses via SharedLibrary/FunctionProvider.getFunctionAddress().
In order to load a JNI library (and have the JVM know about that so that it can resolve native methods to JNI functions), you have to use System.load(), System.loadLibrary(), Runtime.load() or Runtime.loadLibrary().

#3

Ok, thanks for the explanation :slight_smile:

-ClaasJG

#4

The org.lwjgl.system.Library class supports two library loading methods:

  • [icode]SharedLibrary loadNative()[/icode], used for standard native libraries (e.g. GLFW or the OpenGL/Vulkan ICDs).
  • [icode]void loadSystem()[/icode], used for JNI libraries.

Both support the same mechanism for discovering shared libraries from paths (java.library.path / org.lwjgl.librarypath / system paths) or JAR files (automatically extracted to a temp or user-specified folder). Switching from loadNative() to loadSystem() should fix the issue.

#5

Hui, I am to dumb to browse documentation it seems :persecutioncomplex:

It works like a charm now and replaces my hackish code.

-ClaasJG