How do I detect which kind of JRE is installed -- 32bit vs. 64bit

Question

During installation with an NSIS installer, I need to check which JRE (32bit vs 64bit) is installed on a system. I already know that I can check a system property "sun.arch.data.model", but this is Sun-specific. I'm wondering if there is a standard solution for this.

Answer 1

The JVM architecture in use can be retrieved using the "os.arch" property:

System.getProperty("os.arch"); 

The "os" part seems to be a bit of a misnomer, or perhaps the original designers did not expect JVMs to be running on architectures they weren't written for. Return values seem to be inconsistent.

The NetBeans Installer team are tackling the issue of JVM vs OS architecture. Quote:

x64 bit : Java and System

Tracked as the Issue 143434.

Currently we using x64 bit of JVM to determine if system (and thus Platform.getHardwareArch()) is 64-bit or not. This is definitely wrong since it is possible to run 32bit JVM on 64bit system. We should find a solution to check OS real 64-bitness in case of running on 32-bit JVM.

• for Windows it can be done using WindowsRegistry.IsWow64Process()
• for Linux - by checking 'uname -m/-p' == x86_64
• for Solaris it can be done using e.g. 'isainfo -b'
• for Mac OSX it can't be done using uname arguments, probably it can be solved by creating of 64-bit binary and executing on the platform... (unfortunately, this does not work:( I've created binary only with x86_64 and ppc64 arch and it was successfully executed on Tiger..)
• for Generic Unix support - it is not clear as well... likely checking for the same 'uname -m/-p' / 'getconf LONG_BIT' and comparing it with some possible 64-bit values (x86_64, x64, amd64, ia64).

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Sample properties from different JVMs all running on 64bit Ubuntu 8.0.4:

32bit IBM 1.5:

java.vendor=IBM Corporation java.vendor.url=http://www.ibm.com/ java.version=1.5.0 java.vm.info=J2RE 1.5.0 IBM J9 2.3 Linux x86-32 j9vmxi3223-20061001 (JIT enabled) J9VM - 20060915_08260_lHdSMR JIT  - 20060908_1811_r8 GC   - 20060906_AA java.vm.name=IBM J9 VM java.vm.specification.name=Java Virtual Machine Specification java.vm.specification.vendor=Sun Microsystems Inc. java.vm.specification.version=1.0 java.vm.vendor=IBM Corporation java.vm.version=2.3 os.arch=x86 os.name=Linux os.version=2.6.24-23-generic sun.arch.data.model=32 

64bit Sun 1.6:

java.vendor=Sun Microsystems Inc. java.vendor.url=http://java.sun.com/ java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport.cgi java.version=1.6.0_05 java.vm.info=mixed mode java.vm.name=Java HotSpot(TM) 64-Bit Server VM java.vm.specification.name=Java Virtual Machine Specification java.vm.specification.vendor=Sun Microsystems Inc. java.vm.specification.version=1.0 java.vm.vendor=Sun Microsystems Inc. java.vm.version=10.0-b19 os.arch=amd64 os.name=Linux os.version=2.6.24-23-generic sun.arch.data.model=64 

64bit GNU 1.5:

java.vendor=Free Software Foundation, Inc. java.vendor.url=http://gcc.gnu.org/java/ java.version=1.5.0 java.vm.info=GNU libgcj 4.2.4 (Ubuntu 4.2.4-1ubuntu3) java.vm.name=GNU libgcj java.vm.specification.name=Java(tm) Virtual Machine Specification java.vm.specification.vendor=Sun Microsystems Inc. java.vm.specification.version=1.0 java.vm.vendor=Free Software Foundation, Inc. java.vm.version=4.2.4 (Ubuntu 4.2.4-1ubuntu3) os.arch=x86_64 os.name=Linux os.version=2.6.24-23-generic 

(The GNU version does not report the "sun.arch.data.model" property; presumably other JVMs don't either.)

Answer 2

I'm using NSIS and Launch4j to wrap a Java Desktop app. So I need not only to detect any JRE, but the one Launch4j will find with its search algorithm. The only approach that made sense is to run a short Java program within the NSIS installer. Here's the Java:

      public class DetectJVM {         private static final String keys [] = {             "sun.arch.data.model",             "com.ibm.vm.bitmode",             "os.arch",         };         public static void main (String [] args) {             boolean print = args.length > 0 && "-print".equals(args[0]);             for (String key : keys ) {                 String property = System.getProperty(key);                 if (print) System.out.println(key + "=" + property);                 if (property != null) {                     int errCode = (property.indexOf("64") >= 0) ? 64 : 32;                     if (print) System.out.println("err code=" + errCode);                     System.exit(errCode);                 }             }         }     }  

Wrap this with Launch4J. Use the GUI header type but also set to true. Otherwise the error code will be lost. (I put all this in my Netbeans Ant build script.

Here's the matching NSIS code that uses it:

  File ... ; unpack files including detectjvm.exe. ClearErrors ExecWait '"$INSTDIR\detectjvm.exe"' $0 IfErrors DetectExecError IntCmp $0 0 DetectError DetectError DoneDetect DetectExecError:     StrCpy $0 "exec error" DetectError:     MessageBox MB_OK "Could not determine JVM architecture ($0). Assuming 32-bit."     Goto NotX64 DoneDetect: IntCmp $0 64 X64 NotX64 NotX64 X64:     File  ... 64-bit AMD DLLs.     Goto DoneX64 NotX64:     File ... 32-bit x86 DLLs. DoneX64: Delete $INSTDIR\detectjvm.exe  

This has worked fine on a very large variety of machines from WinXP with no SP through Vista and Win7 with all SPs, 32- and 64-bit.

Note that in my NSIS script I'm using an existing package that checks to see if the JVM is installed and does that first, so the default 32-bit selection would only occur if something went badly wrong with the JVM install, in which case the set of DLLs you copy won't matter anyway.

Hope this is helpful to somebody.