Netbeans.conf: what is the variable for the user home? - netbeans

Question

When starting Netbeans, I need to add a system property named mEnvironment and set it as a sub-directory of the user's home. Example: In the netbeans.conf, I would like to add:
netbeans_default_options="-J-XX:+UseStringDeduplication -J-Xss2m -J-DmEnvironment=${USER_HOME}/mySubDirectory ......
USER_HOME is given as example of course.
Does someone know how Netbeans get the user home directory in the netbeans.conf file?
Thank you
Paul

Answer 1

Does someone know how Netbeans get the user home directory in the
netbeans.conf file?
The process is convoluted, and varies by operating system, but is described in great detail within netbeans.conf itself. This is the relevant content for my Apache NetBeans 11.1 installation:
# On Windows ${DEFAULT_USERDIR_ROOT} will be replaced by the launcher
# with "<AppData>\NetBeans" where <AppData> is user's
# value of "AppData" key in Windows Registry under
# "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders"
# and ${DEFAULT_CACHEDIR_ROOT} will be replaced by the launcher
# with "<Local AppData>\NetBeans\Cache" where <Local AppData> is user's
# value of "Local AppData" key in Windows Registry under
# "HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders"
#
# On Mac ${DEFAULT_USERDIR_ROOT} will be replaced by the launcher
# with "~/Library/Application Support/NetBeans" and
# ${DEFAULT_CACHEDIR_ROOT} with "~/Library/Caches/NetBeans"
#
# On other systems ${DEFAULT_USERDIR_ROOT} will be replaced by the launcher
# with "~/.netbeans" and ${DEFAULT_CACHEDIR_ROOT} with "~/.cache/netbeans"
....
netbeans_default_userdir="${DEFAULT_USERDIR_ROOT}/11.1"
However, none of that really helps you, because you cannot access the values of netbeans_default_userdir or DEFAULT_USERDIR_ROOT; they are used internally by NetBeans itself, and are not System properties. You can verify this by displaying the values returned by System.getProperties(); none of the entries in netbeans.conf are shown.
Also, you can't meaningfully add new name/value pairs in netbeans.conf; you can only modify the values of the names used by NetBeans. That file is for NetBeans configuration, not user configuration. So if you add a line containing (say) MyConfSetting="ABC" then NetBeans will simply ignore that, and it won't be accessible to you either.
However, you can use an alternative approach to set a System Property for your directory in your application:
The read-only environment variable APPDATA points to your (operating system's) user directory. On my Windows 10 machine it has the value C:\Users\johndoe\AppData\Roaming.
The default user directory for NetBeans is the value of APPDATA + a sub-directory named NetBeans + a sub-directory named the NetBeans version. On my machine it is C:\Users\johndoe\AppData\Roaming\NetBeans\11.1. See the value of User directory in the Help > About screen for confirmation.
I don't know how to dynamically determine the version of NetBeans, but if that isn't important you can programmatically create a system property specifying your directory path:
String dir = System.getenv("APPDATA") + "\\NetBeans\\mySubDirectory";
System.setProperty("myDir", dir);
System.out.println("myDir=" + System.getProperty("myDir"));
On my machine that println() call displays myDir=C:\Users\johndoe\AppData\Roaming\NetBeans\mySubDirectory. I don't know if that approach meets your requirements, but I don't know of any other simple way to dynamically set your directory name.
Notes:
I checked this on Windows 10. Details may vary on other operating systems, but the overall approach should still work.
You can also specify parameters at run time using {project} > Properties > Run > Arguments (e.g. arg1=%APPDATA%\NetBeans\MyDir) and {project} > Properties > Run > VM Options (e.g. -Dvmopt1=%APPDATA%\NetBeans\MyDir), but that approach won't work because the %APPDATA% is simply treated as the literal "%APPDATA%" rather than evaluated as an environment variable.