Trying to use DLL from Java (JNA). Unable to load library exception

问题

I have NetBeans project from tutorial which causes exception:

Exception in thread "main" java.lang.UnsatisfiedLinkError: Unable to load library 'simpleDLL': The specified module could not be found.

Tried to put simpleDLL.dll in project libraries, copied file in system32 folder with no success.

回答1:

I had exactly the same problem with loading a DLL, I solved it in this way:

As Christian Kuetbach said, check if the simpleDLL you are using is compatible with your processor's architecture, a 32-bit DLL won't work on a 64-bit machine, and also a 64-bit DLL won't work on a 32-bit machine.
If the DLL is compatible, then the problem may be in your java library path. I put my DLL into the user.dir directory and then I used this code:

Set Java library path to user.dir or maybe another path you want:
```
String myLibraryPath = System.getProperty("user.dir");//or another absolute or relative path

System.setProperty("java.library.path", myLibraryPath);
```
Load the library:

System.loadLibrary("libraryWithoutDLLExtension");

It worked for me, try it and tell me if it works for you.

回答2:

Please check if the simpleDLL is 32 or 64 bit. Then check, if the JVM is also 32 or 64 bit. They have to be for the same platform.

You may also specify an absolute path, if you change loadLibrary() to load(): http://www.chilkatsoft.com/p/p_499.asp

回答3:

I could only run in 32bit (Xp).

Place the DLL in the folder "c:\Windows\System32"

helloWorldDLL lib = (helloWorldDLL) Native.loadLibrary("helloworldDLL", helloWorldDLL.class);

If the error java.lang.UnsatisfiedLinkError: Unable to load library" persists, use Dependency Walker to view the dependent DLLs.

Dependency Walker

回答4:

Three possible reasons for this issue, if the dll file is not broken:

32 bit 64 bit Compatibility. 32bit dll can only be running on a 32bit jdk or jre. By using Cygwin command file <filename> we can tell if a dll is 32bit or 64bit.
the dll is not lacated in the right path, so java cannot locate it. Generally speaking we can use some absolut path other than System32 to ensure that the path is right.
the dll that we are loading is requires other dlls.

How can we handle the 3rd possibility:

using JNI's System.loadLibrary() mthod can give me more hint, compared with JNA. It may says something like: Exception in thread "main" java.lang.UnsatisfiedLinkError: MyLibrary.dll: Can't find dependent libraries. It means some libraries MyLibrary.dll depends is missing. By using dependency walker we can tell what dlls are needed.
By loading these dlls before the dll that we want to load, we can solve this issue.

回答5:

Had the same problem and for some reason even if the dll filename has uppercase letters, you have to load it using all lowercase letters like this: Native.loadLibrary("dlls/library.dll", YourInterface.class)

NOT this: Native.loadLibrary("dlls/Library.dll", YourInterface.class)

来源：https://stackoverflow.com/questions/14286647/trying-to-use-dll-from-java-jna-unable-to-load-library-exception

标签

java

dll

jna