Using JNA with IBM J9 JVM

Question

The first difficulty in using JNA with J9 is that the J9 JVM does not include the java.awt package and the Native class imports a few classes from this package. This is easily overcome by downloading the JNA source, ripping out these imports and their dependent methods (which I am not using anyway), and building a new JNA jar.

Here is a simple test program:

    public class TestJni {
        public static void main(String[] args) {
            CLibrary instance = (CLibrary) Native.loadLibrary((Platform.isWindows() ? "msvcrt" : "c"), CLibrary.class);     
            instance.printf("Hello, World\n", new Object[] {});
        }

        // This is the standard, stable way of mapping, which supports extensive
        // customization and mapping of Java to native types.
        public interface CLibrary extends Library {        
            void printf(String format, Object[] args);
        }
    }

After correcting the java.awt problem, I receive the error:

Caused by: java.lang.UnsatisfiedLinkError: C:\DOCUME~1\TSO0112\LOCALS~1\Temp\jna72681.dll (Incompatible JNI version (not 1.1, 1.2 or 1.4))
at java.lang.ClassLoader.loadLibraryWithPath(ClassLoader.java:973)
at java.lang.System.load(System.java:459)
at com.sun.jna.Native.loadNativeLibraryFromJar(Native.java:696)
at com.sun.jna.Native.loadNativeLibrary(Native.java:620)
at com.sun.jna.Native.<clinit>(Native.java:104)
at java.lang.J9VMInternals.initializeImpl(Native Method)
at java.lang.J9VMInternals.initialize(J9VMInternals.java:187)
at TestJni.main(TestJni.java:8)

What does it mean by "Incompatible JNI version"? Has anybody out there got J9 to play nice with JNA?

UPDATE: I think JNA is suppressing the following NoClassDefFoundError on trying to load the java.nio.Buffer class because J9 apparently does not have the NIO package included:

JNA: Problems loading core IDs: java.nio.Buffer
Exception in thread "main" java.lang.NoClassDefFoundError: java.nio.Buffer
    at java.lang.ClassLoader.loadLibraryWithPath(Native Method)
    at java.lang.ClassLoader.loadLibraryWithPath(ClassLoader.java:965)
    at java.lang.System.load(System.java:459)
    at TestJni.main(TestJni.java:8)

Answer 1

I have been working with JNA on j9 for a couple of months now. I have had a few small niggles here and there but things mostly seem working fine.

First - The latest versions of JNA(3.2.7) seem to import awt. I am using 3.2.4 and the awt imports are commented out. I think that will work out of the box for you.

Second - THe version of J9 i am working with is for WinCE and it is a JVM for java 1.4. Latest JNA though is built off of java 1.5. So you might want to check which version of java your version of j9 is built on. JNA 3.2.4 is compatible with java 1.4 I believe.

Answer 2

You can also simply provide your own stub implementations of the java.nio/java.awt stuff and simply avoid using those features (mainly direct buffer stuff and obtaining a handle to a native window).