Java Native Interface 32 bit dll on 64 bit system

Question

E:\Code\Java\JNITest>java test Exception in thread "main" java.lang.UnsatisfiedLinkError: E:\Code\Java\JNITest\test.dll: Can't load IA 32-bit .dll on a AMD 64-bit platform     at java.lang.ClassLoader$NativeLibrary.load(Native Method)     at java.lang.ClassLoader.loadLibrary0(Unknown Source)     at java.lang.ClassLoader.loadLibrary(Unknown Source)     at java.lang.Runtime.loadLibrary0(Unknown Source)     at java.lang.System.loadLibrary(Unknown Source)     at test.main(test.java:16)` 

While using Java Native Interface I ran into a problem that generated this error. I believe this is because I compiled the .dll with MinGW which compiles to a 32-bit .dll whilst my system is 64-bit and thus my Java runs at 64-bit. Is there anyway to force my Java to run at 32-bits?

Answer 1

You'll have to install a 32bit JVM and you will be able to run your code.

If you are going to distribute your application, you will want to build both 32bit and 64bit versions of your DLL. Then use the following technique to have the proper DLL loaded regardless of your customers arch. Append either a 32 or a 64 (MyJniDLL32.dll & MyJniDLL64.dll) to your generated output file.

    String archDataModel = System.getProperty("sun.arch.data.model");     System.loadLibrary(libraryName+archDataModel); 

Answer 2

Just to state the obvious: to load a native library built for a 32bit architecture, you have to force the JVM to start in 32bit mode.

java -d32 ... 

Possibly you need to install an older JVM for your platform (eg. Oracle's Java 7 on OS X is 64bit only, you need to get Apple's Java 6 from their knowledge base).