[转] 关于System.getProperty("os.arch")

Java's "os.arch" System Property is the Bitness of the JRE, NOT the Operating System
By Mark Kolich on October 19, 2009 11:15 AM | No TrackBacks

原文:http://mark.koli.ch/2009/10/javas-osarch-system-property-is-the-bitness-of-the-jre-not-the-operating-system.html
参考:http://lopica.sourceforge.net/os.html

If you ever use Java to check if a system is 32 or 64-bit, you should know that Java's "os.arch" system property returns the bitness of the JRE, not the OS itself.  Sites like this are WRONG; any resource that claims Java's "os.arch" property returns the real "architecture of the OS" is lying.  Case in point, I recently ran this tiny program on a 64-bit Windows 7 machine, with a 32-bit JRE:

import com.sun.servicetag.SystemEnvironment;

public class OSArchLies {
  
  public static void main(String[] args) {
    
    // Will say "x86" even on a 64-bit machine
    // using a 32-bit Java runtime
    SystemEnvironment env =
        SystemEnvironment.getSystemEnvironment();
    final String envArch = env.getOsArchitecture();
    
    // The os.arch property will also say "x86" on a
    // 64-bit machine using a 32-bit runtime
    final String propArch = System.getProperty("os.arch");
    
    System.out.println( "getOsArchitecture() says => " + envArch );
    System.out.println( "getProperty() says => " + propArch );
    
  }

}

The output from this tiny app on a 64-bit box:

#/> java OSArchLies
getOsArchitecture() says => x86
getProperty() says => x86

In this case, one would expect to see something like "x86_64" or "amd64" instead of just "x86".  Bottom line, don't believe what you read online about "os.arch" and other Java system properties.  They are usually properties of the JRE/JDK itself, and not necessarily the real properties of the underlying OS or architecture.  If you need to check if a system is actually 32 or 64-bit, you should look elsewhere in the system registry or write your own native app and call it from Java.http://mark.koli.ch/2009/10/reliably-checking-os-bitness-32-or-64-bit-on-windows-with-a-tiny-c-app.html