Java：System.getenv（“APPDATA”）返回null，现在是什么？

Question

I just found out that when a Java program is launched on Windows via "Run As..." (from the executable's context menu) as a different user, a call to System.getenv("APPDATA") will return null , rather than the usual application data folder.

Now, I'm kind of a noob when it comes to Windows folders and such, so my question is, how should I deal with this situation when my program has to be able to store its data somewhere in order to work correctly? More specifically, if System.getenv("APPDATA") returns null , am I even allowed to store any data at all, and if so, where? Thanks in advance!

Answer 1

Okay, I solved my own problem using JNA:

com.sun.jna.platform.win32.Shell32Util.getFolderPath(int nFolder)

where nFolder = 0x001a for the application data folder and nFolder = 0x001c for the local application data folder. On Windows XP, the output is

C:\\Documents and Settings\\[UserName]\\Application Data

C:\\Documents and Settings\\[UserName]\\Local Settings\\Application Data

Most importantly, this does not return null when the program is launched via Run As .

Answer 2

另外，如果你在windows中设置一个环境变量，我注意到在我重新启动操作系统之前java没有提取它。

Answer 3

Yes you are always allowed to store data. You can use temp directory to store you data. You can get temp directory by System.getProperty("java.io.tmpdir"); .