ObjectFactory.fetchObject(Class<T> comInterface) throws exception instead of returning null

[cbbravo]

From my understanding, this method should only return a Proxy if an instance of the requested application is already running.
But instead, it throws an exception. This is not the expected behaviour of a get/fetch method.
Throwing an exception here would point to some internal problems, which do not appear in either cases.

It also makes checking for a running app more complicated than necessary.

My solution: simply replace the call

COMUtils.checkRC(hr);
with the check
if(COMUtils.FAILED(hr)) return null;

	/**
	 * Gets and existing COM object (GetActiveObject) for the given progId and
	 * returns a ProxyObject for the given interface.
	 */
	public <T> T fetchObject(Class<T> comInterface) {
                assert COMUtils.comIsInitialized() : "COM not initialized";
            
                ComObject comObectAnnotation = comInterface.getAnnotation(ComObject.class);
                if (null == comObectAnnotation) {
                        throw new COMException(
                                        "createObject: Interface must define a value for either clsId or progId via the ComInterface annotation");
                }
                final GUID guid = this.discoverClsId(comObectAnnotation);

                final PointerByReference ptrDisp = new PointerByReference();
                WinNT.HRESULT hr = OleAuto.INSTANCE.GetActiveObject(guid, null, ptrDisp);

                // COMUtils.checkRC(hr);
		if(COMUtils.FAILED(hr)) return null;

                Dispatch d = new Dispatch(ptrDisp.getValue());
                T t = this.createProxy(comInterface, d);
                //GetActiveObject returns a pointer to COM object with a +1 reference count, so we must drop one
                //Note: the createProxy adds one
                d.Release();

                return t;
	}

In addition, you should also add a method fetchOrCreateObject(), like this.

	public <T> T fetchOrCreateObject(final Class<T> comInterface) {
		T ret = fetchObject(comInterface);
		if(ret != null) return ret;
		
		return createObject(comInterface);
	}

[matthiasblaesing]

Please have a look at PR #903 I'm reluctant to disable the error handling path in this case. You'd need to analyze the hresult of the call to decide whether or not a "real" error is present. The behavior is in line with the C# bindings (see the example section here: http://157.56.25.106/en-us/library/system.runtime.interopservices.marshal.getactiveobject(VS.90).aspx).

The described behavior can be accomplished by handling the COMException and checking the HRESULT. See the commit message for the first commit in the PR:
2581ef6

[matthiasblaesing]

I consider this fixed by PR #903.