Variant arguments & com function calls

I would like to thank everyone for responding to my questions. I will comment 
on a couple of the responses at a time below. 
 
> 
>public static final int DISP_E_PARAMNOTFOUND = 0x80020004; 
> 
> 
>For now you can use this to create a variant for optional arguments
>(code 
>below not tried by me...): 
> 
>Variant missing = new Variant(); 
>v.vt = VarType.VT_ERROR; 
>v.scode = 0x80020004; 
> 
 
I will try this code as soon as I get a chance tomorrow and will inform the 
list of the results.
 
> 
>If that works for you, then we should probably add 
> 
>public class Variant { 
>... 
>public static final Variant MISSING = new Variant(); 
>static { 
> MISSING.vt = VarType.VT_ERROR; 
> MISSING.scode = COMException.DISP_E_PARAMNOTFOUND; 
>} 
> 
>So that you can use Variant.MISSING for optional VARIANT args. 
> 

I also wanted to suggest some improvements to the Variant class. In general, 
now when I have to use a Variant, first I have to create a new instance with 
"new", and then assign the appropriate value using the appropriate setter 
method. I was wondering, if in general, a few 'convenience' constructors could 
be added in which the constructor arguments would be assigned into the 
appropriate value of the Variant instance e.g. new Variant(int intValue) 
assigns the boolValue to the bool value in the class. Certainly, it wouldn't 
make any to creae a constructor for each possible field in invariant, but it 
would be nice if there is one for some. 
 
>It should generally not be necessary to generate instances of 
>org.jawin.Variant. Most (if not all) marshalling will be handled 
>correctly by the automatic marshalling and the dispatch coercion 
>mechanism. Eg. java.lang.Integer -> VT_UI4. 

I can certainly confirm that the automatic marshalling and dispatch coercion 
works well when working directly with DispatchPtr-s and such ( I use it mostly 
from Jython and it works exceptionally well) . However, when I generated the 
Java classes using the com browser ( I generated them with the release version, 
I am not sure if the cvs version would generate differently), the Java method 
calls are generated, with Variant arguments, so if I use the generated Java 
hierarchy ( I generated class hierarchies for Excel and Word . I noticed that 
there were a few Win32 structures & others in cvs - should generated code for 
MS Office to CVS ? In general, the generation worked pretty smoothly with the 
release version however, I had to fix a few methods and arguments that didn't 
compile. I understand that in the general case, the code generation should work 
flawlessly; however, for newcomers to the project it will certainly add value 
to have a generated and working interface to MS Office). 
 
> 
>We don't have that pt. You can try with "null", which get marshalled 
>into VT_NULL, but I assume we need to marshal into VT_EMPTY to get
>this 
>to work? But at least it sounds like it is something we have to
>support. 

Using null (that gets marshalled to VT_NULL) definitely doesn't work as a 
substitute for the optional argument ( I get some kind of com exception). 
 
> 
>Hope this helps you a little bit. And as a sidenote, as I don't know 
>exactly what you are trying to do with Excel, but have you checked
>the 
>POI project http://jakarta.apache.org/poi/, for writing/reading
>Excel 
>files?. 

I had looked at POI in the past, and it certainly does look convenient for 
Excel and Word. However, I am quite impressed with Jawin at this point and 
would like to use the opportunity as a springboard for learning more on 
invoking other (non-Com based) native win32 functionality from Java. I read 
over the extended how-tos and it is starting to make a lot more sense ( I was 
even thinking of going over a Win32 programming book that I have and 
implementing the examples in Java / Jawin). 
 
 

 
Regards,

Alex Kotchnev
Developer / Systems Analyst
Diversified Information Technologies

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