Java App can't write on disk on Windows 7, why?

Question

I wrote a Java app and I packaged it with NSIS (or NSYS...) installer. I works cleanly but sometimes I found that for some users running on Windows 7, the app won't be able to write on disk at all (it can't even write the log). The app is installed on c:\Programs (or d or e...). People from support say that they solve it by installing in c:\ . Why does this happen? Is it related to Java security? Maybe on my Windows installation and others I don't notice it because I have UAV turned off.

Ideas?

*"I have UAV turned off."* [UAV](http://en.wikipedia.org/wiki/Unmanned_aerial_vehicle)? No remote flying for you! What is NSYS? — Andrew Thompson, Dec 13 '11 at 10:11
NSYS is your new installer overlord.... is a typo of http://nsis.sourceforge.net/Main_Page — gotch4, Dec 14 '11 at 10:20

score 4 · Accepted Answer · edited May 23 '17 at 11:44

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You have hit the nail on the head when you wonder if it is because you have UAC switched off.

You should not be writing the log file to the location that the application is installed to, instead you will need to pick a location that is writable by the app, e.g. A directory below the user.home system property.

The reason that java applications can't do this and other applications can is related to Data Redirection, which causes writes to certain folders to be transparently redirected to a per-user store of data. I think this redirection is disabled for the JRE (checked using process explorer, which does not have a marking of 'Virtualized') which means that on java programs the transparent redirection will not happen.

If you want your application to be able to write into the install directory of the application, then the easiest way to accomplish this is to change the permissions of the folder on installation.

edited May 23 '17 at 11:44

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answered Dec 13 '11 at 08:45

Anya Shenanigans

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I was not asking for a solution, rather I wanted to know why does that happen with java, while other apps can do it. Of course I can write in user dir... but I wanted to know more about the permission thing – gotch4 Dec 13 '11 at 13:38
Data writing to the program files directory is transparently redirected to the current user's appdata. You can see it by going to "%appdata%\..\local\VirtualStore". Transparent redirection happens for most programs because they are running out of the directory they are installed. However in the case of java programs, they are technically running out of java's program directory since they piggy back on the java interpreter (java.exe or javaw.exe). To prevent someone from maliciously overwriting the java.exe's or settings, they have disabled the visualization entirely. Its a security feature. – Ape-inago Apr 16 '13 at 17:29

score 0 · Answer 2 · answered Jun 16 '12 at 17:37

I did some research and found in a different forum that Program Files is a protected directory for Windows 7 Home Premium, you have to install c:\ because of Windows Security. Just FYI

I was trying to code on Tomcat and found that I couldn't save files to Program Files. I had to install c:\Tomcat to be able to save any of my files.

score 0 · Answer 3 · answered Dec 13 '11 at 08:57

The application apparently does not have write access to the location where tries to write the file. If it tries to write to the Program Files directory, that's to be expected (applications are not usually run with administrator rights). Instead write to a place which is guaranteed to be writable by the application/current user. For example get the Java property user.home which will point to the user's home directory, and write the files there in an appropriate subdirectory.

Java App can't write on disk on Windows 7, why?

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