Java : switching between dll depends on system architecture (32/64)

Question

I have a Java program uses some dlls. As these embeded dlls have to be built for a specific system architecture (32 or 64bits) I want to make a method/something that allow my program to switch between 32/64 bits version of dlls (or disable the library load if the program run on a 64 bits system)

I hope there is a solution different from making two versions of the program

Thanks in advance, Damien

score 6 · Answer 1 · answered Mar 21 '11 at 15:17

6

Use system properties:

if ("x86".equals(System.getProperty("os.arch"))) {
   // 32 bit
} else if ("x64".equals(System.getProperty("os.arch"))) {
   // 64 bit
}

answered Mar 21 '11 at 15:17

Vladimir Ivanov

42,730
18
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1

Okay, and what happens on my old PPC Mac? – Sean Patrick Floyd Mar 21 '11 at 15:28
3

Just make another if? I think that idea is rather clear, this is just a sample of code. – Vladimir Ivanov Mar 21 '11 at 15:31
1

os.arch is amd64 on my machine – mjaggard Apr 30 '15 at 12:28

score 3 · Answer 2 · answered Mar 21 '11 at 15:27

You can use the System Property sun.arch.data.model

String dataModel = System.getProperty("sun.arch.data.model");
if("32").equals(dataModel){
    // load 32-bit DLL
}else if("64").equals(dataModel){
    // load 64-bit DLL
}else{
    // error handling
}

Careful: this property is defined on Sun VMs only!

Reference:

Java HotSpot FAQ > When writing Java code, how do I distinguish between 32 and 64-bit operation?

score 2 · Answer 3 · answered Mar 21 '11 at 16:05

A brute force way is to run

boolean found = false;
for(String library: libraries)
    try {
        System.loadLibrary(library);
        found = true;
        break;
    } catch(UnsatisfiedLinkError ignored) {
    }
if(!found) throw new UnsatifiedLinkError("Could not load any of " + libraries);

score 1 · Answer 4 · answered Mar 21 '11 at 15:26

1

If you're using OSGi and JNI, you can specify the DLLs appropriate for different platforms and architectures in the manifest via Bundle-NativeCode.

For example:

    Bundle-NativeCode: libX.jnilib; osname=macOSX, X.dll;osname=win32;processor=x86

answered Mar 21 '11 at 15:26

Andy Thomas

84,978
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what about libraries having the same name? I have to import the rxtx library for both ARM and x86 architectures and the library is called librxtxSerial.so in both cases. How can i distinguish them using this header?? – wyr0 Sep 16 '15 at 15:53
@marbal - I think you would list the library twice, once for `processor=86`, and once for `processor=ARM_le` (for little-endian) or `processor=ARM_be` (for big-endian). These values and others can be found in the table at http://www.osgi.org/Specifications/Reference#processor . – Andy Thomas Sep 16 '15 at 18:39
I've created a folder named "lib" and 2 subfolders called "x86" and "arm" and i've put in each of them the libraries built respectively for processors x86 and arm. Then, in the header, i've wrote this: `lib/x86/librxtxSerial.so; processor=x86, lib/arm/librxtxSerial.so; processor=ARM_le` but every time i get the same error: `No match found for native code: ` . What i'm doing wrong? – wyr0 Sep 17 '15 at 08:22
i've descriibed the problem here: http://stackoverflow.com/questions/32625924/osgi-bundle-nativecode-give-error-no-match-found-for-native-code – wyr0 Sep 17 '15 at 08:58

score 0 · Answer 5 · answered Mar 21 '11 at 15:19

Define a java interface that represents your DLL API and provide two implementations, one that calls the 32 bit DLL and another one that calls the 64 bit version:

public interface MyDll {
    public void myOperation();
}

public class My32BitDll implements MyDll {
    public void myOperation() {            
        // calls 32 bit DLL
    }
}

public class My64BitDll implements MyDll {
    public void myOperation() {            
        // calls 64 bit DLL
    }
}

public class Main {
    public static void main(String[] args) {
        MyDll myDll = null;

        if ("32".equals(args[0])) {
            myDll = new My32BitDll();
        } else if ("64".equals(args[0])) {
            myDll = new My64BitDll();
        } else {
            throw new IllegalArgumentException("Bad DLL version");
        }

        myDll.myOperation();
    }
}

I doubt that this is what the OP wants. And it forces the user to tell the program whether it runs in a 32 bit or 64 bit environment. The program should discover that itself. — Christian Hujer, Mar 11 '15 at 18:34

Java : switching between dll depends on system architecture (32/64)

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