Detect the location of AppData\LocalLow with JNA

Question

I'm trying to detect the location of AppData\LocalLow work on Java with JNA on Windows 7. But the closest function available for the job is:

W32API.HRESULT SHGetFolderPath(W32API.HWND hwndOwner,int nFolder,W32API.HANDLE
                               hToken,W32API.DWORD dwFlags,char[] pszPath)

Here we have the Solution in C#

But in my case, JAVA + JNA, I'm wondering how I can use the LocalLow GUID with SHGetFolderPath only, or maybe I should look at the problem from a different angle (maybe JNI would be better here?)

If somebody can help on that, thanks

Cheers

EDIT: Ok, now I added SHGetKnownFolderPath, but here, it keeps returning me strings like that "?f"

static interface Shell32 extends Library {

    public static final int     MAX_PATH            = 260;
    public static final String  FOLDERID_APPDATALOW = "{A520A1A4-1780-4FF6-BD18-167343C5AF16}";

    static Shell32 INSTANCE = (Shell32) Native.loadLibrary("shell32",
                    Shell32.class, OPTIONS);

    public int SHGetKnownFolderPath(Guid.GUID rfid, int dwFlags, HANDLE hToken,
                    char[] pszPath);
}

public static void main(String[] args) {

   char[] pszPath = new char[Shell32.MAX_PATH];
   Guid.GUID localLowId = Ole32Util.getGUIDFromString(Shell32.FOLDERID_APPDATALOW);
   int hResult = Shell32.INSTANCE.SHGetKnownFolderPath(localLowId, 0, null, pszPath);

   if (hResult == 0) {
       String path = new String(pszPath);
       int len = path.indexOf('\0');
       path = path.substring(0, len);
       System.out.println(path);
   } else {
       System.err.println("Error: " + hResult);
   }

}

You likely need to extend StdCallLibrary rather than Library, since w32 API uses the stdcall calling convention. — technomage, Jul 08 '11 at 00:27

Sith Nazgûl Cat · Answer 1 · 2012-08-22T21:46:54.910

This Question is Somewhat old However I managed to Solve this issue. allow me to explain why Kyro approach does not work quite well. This is due
SHGetKnownFolderPath uses a POINTER and not a String or A character array (that why show odd output) . therefore you need to use something like this:

public int SHGetKnownFolderPath(Guid.GUID rfid, int dwFlags, HANDLE hToken, PointerByReference pszPath); a pointer by reference...

so on this case i attach a example I used:

static interface Shell32 extends StdCallLibrary {
    public static final String  FOLDERID_APPDATALOW = "{A520A1A4-1780-4FF6-BD18-167343C5AF16}";

    static Shell32 INSTANCE = (Shell32) Native.loadLibrary("shell32",
                    Shell32.class, W32APIOptions.UNICODE_OPTIONS);

    public int SHGetKnownFolderPath(Guid.GUID rfid, int dwFlags, HANDLE hToken,
                    PointerByReference pszPath);
}

public static void main(String[] args) {
   Guid.GUID localLowId = Ole32Util.getGUIDFromString(Shell32.FOLDERID_APPDATALOW);
   PointerByReference e= new PointerByReference();
   int hResult = Shell32.INSTANCE.SHGetKnownFolderPath(localLowId, 0, null, e);

   if (hResult == 0) {
       char delim='\0';
       char Array[]=e.getValue().getCharArray(0,255);
       for (int i = 0; i < Array.length; i++) {
         if(Array[i]==delim){
             char temparr[]=new char[i];
             System.arraycopy(Array,0,temparr,0,i);
             Array=temparr;
             break;
         }  
       }
       /*dont forget to release the Pointer*/
       Ole32.INSTANCE.CoTaskMemFree(e.getValue());
       System.out.println(Array);
   } else {
       System.err.println("Error: " + hResult);
   }

}
private static interface Ole32 extends StdCallLibrary {

    Ole32 INSTANCE = (Ole32) Native.loadLibrary(
            "Ole32", Ole32.class, W32APIOptions.UNICODE_OPTIONS);

    void CoTaskMemFree(Pointer pv);
}

Thanks for your answer but I ended up using Cache.getCacheDir() from deploy.jar : http://javasourcecode.org/html/open-source/jdk/jdk-6u23/com/sun/deploy/cache/Cache.html (I mainly wanted access to LocalLow to get the java cache folder...) — Kyro, Aug 28 '12 at 18:17

score 1 · Answer 2 · answered May 10 '11 at 16:59

You can extend Shell32 (or create your own similar class) to get access to the SHGetKnownFolderPath API:

W32API.HRESULT SHGetKnownFolderPath(
                          Guid.GUID rfid, 
                          W32API.DWORD dwFlags, 
                          W32API.HANDLE hToken, 
                          char[] pszPath);

Detect the location of AppData\LocalLow with JNA

2 Answers2