How to check if document is still open

Question

I have the following problem with Adobe Acrobat Standard 9:
I have a Java Applet that uses Adobe Acrobat to present documents to the user. The user is able to edit and save the document. When the user closes the document the document is stored in a database and therefore I somehow have to listen for when the document is closed to determine when to save the docuent in the database.
The "listener" is implemented in a thread that executes every 500 ms. I use a product called Java2COM (NevaObject Technology) to communicate with the Adobe Object-model in Windows. The code to determine if the document is still open has this implementation:
private boolean isValid() {
     synchronized (READ) {
          if (mDoc == 0) { //mDoc is the document registered in the COMIGlobalInterfaceTable
               return false;
     boolean valid = false;
     COMIDispatch document = new COMIDispatch();
     COMDispParams params = null;
     COMVariant ans = null;
     try {
          COMIGlobalInterfaceTable.GetInterface(mDoc, document);
          params = new COMDispParams();
          ans = new COMVariant();
          COMExcepInfo exc = new COMExcepInfo();
          document.Invoke("IsValid",
               COMIDispatch.LOCALE_SYSTEM_DEFAULT,
               COMIDispatch.DISPATCH_METHOD,
               params, ans, exc);
          valid = ans.asBoolean();
          } catch (COMException e) {
               valid = !COM.isComAppAvslutad(e.hresult().getValue());
          } finally {
               clear(params);
               clear(ans);
               release(document);
          return valid;
A big part of the problem is that I have not managed to reproduce the problem in test mode... the problem occurs (so far) only in production mode.
Most part of the code above is Java2COM-specific so my main question is this: Is using the method 'IsValid' in Acrobat's COM/OLE-api the correct way to check if a document is open/showed in Adobe Acrobat?

Answer 1

Yes, but my problem is that I don't know at what point the user closes the document. For example:
The user creates a new document (pdf) in my Java Applet.
The Java Applet launches Acrobat Standard which presents a document to the user.
The user edits the document, saves and then closes the document.
The document is now to be stored in a document database... and therefore I have to somehow "listen" for when the document has been closed, I can't store it in the database before it has been properly closed.
So what I do (or try to do) is ask Acrobat Standard if the document is still open in Acrobat Standard by calling its method IsValid in the COM-api. This is done in a thread that executes every 500 ms.
There may be better ways to achieve this so any suggestion is appreciated.