hooking into system shutdown in Windows?

[Noel Grandin]

Hi

Has anybody successfully hooked into the Windows shutdown messages? I've been beating my head against this for a while, and I just can't seem to get anything useful.

I definitely seem to be getting normal windows messages, but I never seem to receive the critical WM_ENDSESSION message.

Thanks, Noel Grandin

public class ShutdownDetect

{

/**

* @see <a href="http://msdn.microsoft.com/en-us/library/aa376889.aspx">WM_ENDSESSION reference</a>

*/

public static final int WM_ENDSESSION = 0x16;

public static final int WM_QUERYENDSESSION = 0x11;

public interface IShutdownListener

{

void onShutdown();

}

public static class CWPSSTRUCT extends Structure

{

public LPARAM lParam;

public WPARAM wParam;

public DWORD message;

public HWND hwnd;

}

public interface WinHookProc extends WinUser.HOOKPROC

{

/**

* @see <a href="http://msdn.microsoft.com/en-us/library/windows/desktop/ms644975(v=vs.85).aspx">CallWndProc

*      callback function</a>

* @param nCode is an action parameter. anything less than zero indicates I should ignore this call.

* @param wParam Specifies whether the message was sent by the current thread. If the message was sent by the

*          current thread, it is nonzero; otherwise, it is zero

* @param hookProcStruct A pointer to a CWPSTRUCT structure that contains details about the message.

* @return If nCode is less than zero, the hook procedure must return the value returned by CallNextHookEx.

*/

WinDef.LRESULT callback(int nCode, WinDef.WPARAM wParam, CWPSSTRUCT hookProcStruct);

}

public static final class MyHookProc implements WinHookProc

{

public IShutdownListener listener;

public WinUser.HHOOK hhook;

@Override

public LRESULT callback(int nCode, WPARAM wParam, CWPSSTRUCT hookProcStruct) {

if (nCode >= 0) {

System.out.println(hookProcStruct.message);

// tell the OS it's OK to shut down

if (hookProcStruct.message.longValue() == WM_QUERYENDSESSION) {

System.out.println("WM_QUERYENDSESSION");

return new LRESULT(1);

}

// process the actual shutting down message

if (hookProcStruct.message.longValue() == WM_ENDSESSION) {

System.out.println("WM_ENDSESSION");

listener.onShutdown();

return new LRESULT(0); // return success

}

}

// pass the callback on to the next hook in the chain

return User32.INSTANCE.CallNextHookEx(hhook, nCode, wParam, hookProcStruct.getPointer());

}

}

public static void register(JFrame frame, final IShutdownListener listener) {

Native.setCallbackExceptionHandler(new Callback.UncaughtExceptionHandler() {

@Override

public void uncaughtException(Callback arg0, Throwable arg1) {

arg1.printStackTrace();

}

});

// get the window handle for the main window/frame

final HWND hwnd = new HWND();

hwnd.setPointer(Native.getComponentPointer(frame));

// clear the error value

Native.setLastError(0);

// retrieve the threadID associated with the main window/frame

int windowThreadID = User32.INSTANCE.GetWindowThreadProcessId(hwnd, null);

if (windowThreadID == 0) {

int x = Native.getLastError();

throw new IllegalStateException(

"error calling GetWindowThreadProcessId when installing machine-shutdown handler " + x);

}

// clear the error value

Native.setLastError(0);

final MyHookProc proc = new MyHookProc();

proc.listener = listener;

proc.hhook = User32.INSTANCE.SetWindowsHookEx(12/* WH_CALLWNDPROCRET */, new MyHookProc(),

null, windowThreadID/* dwThreadID */);

// null indicates failure

if (proc.hhook == null) {

int x = Native.getLastError();

throw new IllegalStateException(

"error calling SetWindowsHookEx when installing machine-shutdown handler " + x);

}

System.out.println("Installed shutdown-detect hook procedure");

}

public static void main(String[] args) {

final JFrame frame = new JFrame("Shutdown Test");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.setVisible(true);

register(frame, new IShutdownListener() {

@Override

public void onShutdown() {

try {

PrintStream out = new PrintStream(new File("C:/SCC_Runtime/shutdownTest.txt"));

System.out.println("shutting down");

out.println("shutting down");

out.close();

}

catch (IOException ex) {}

System.exit(1);

}

});

}

}

[Timothy Wall]

The VM may be getting a message before your application code does. Just an idea.

[Noel Grandin]

On Wednesday, June 13, 2012 1:20:57 PM UTC+2, Timothy Wall wrote:

The VM may be getting a message before your application code does.  Just an idea.

Thanks. Some digging around in the bowels of the AWT C++ code indicates that this is probably the case.

Oh well. 

[Noel Grandin]

On Wednesday, June 13, 2012 1:20:57 PM UTC+2, Timothy Wall wrote:

The VM may be getting a message before your application code does.  Just an idea.

Mr Wall, you, sir, are a genius!!

Thanks to that hint, I figured out that I need to modify this line of code

               proc.hhook = User32.INSTANCE.SetWindowsHookEx(12/* WH_CALLWNDPROCRET */, proc, 

                                null, windowThreadID/* dwThreadID */); 

to this

proc.hhook = User32.INSTANCE.SetWindowsHookEx(4/* WH_CALLWNDPROC */, proc,

null, windowThreadID/* dwThreadID */);

Note the critical first parameter. By installing the hook BEFORE the normal windows procedure, I can see the relevant events.

[Muhammed Yuce]

Your CWPSSTRUCT class is wrong. This class should be:

   public static class CWPSSTRUCT extends Structure {

        public WinDef.LPARAM lParam;
        public WinDef.WPARAM wParam;
        public int message;
        public WinDef.HWND hwnd;

        @Override
        protected List<?> getFieldOrder() {
            return Arrays.asList("lParam", "wParam", "message", "hwnd");
        }
    }

[Timothy Wall]

Pull requests with associated tests (where possible) are welcome.

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[Muhammed Yuce]

Noel Grandin, When I run your codes, JVM crashes. Do you know the reason?