onSuccess() return value other than void?

[day_trader]

At present, an AsyncCallback contains a 'public void onSuccess()'
method. This is posing significant problems for me at the moment.

I have a method myMethod() being called which has a return value type
of ArrayList<String>. MyMethod contains this AsynCallback which is
used to query a database on the server side of the code. I need to,
either somehow make the method WAIT for the AsyncCallback's
onSuccess() method to return which is the thing that is giving me the
ArrayList<String> to return to the code which called myMethod, or
change the return type of the AsyncCallback to ArrayList<String> and
let this be the 'return' of myMethod.

Is this possible? Am I very confused? Could someone please advise?

[andreas]

Welcome to the async world! ;-)

I had the same problem. Since the code of an async callback is not
executed in the order of the statements in your myMethod() you can not
directly return the results from onSuccess() in myMethod(). And
myMethod() is not able to "wait" for onSuccess().

You could for example do the things you want to do with
ArrayList<String> in onSuccess() instead of where you call myMethod()
of if you want to keep the processing logic for ArrayList<String>
where myMethod() is called use a method to pass ArrayList<String> from
onSuccess().

You can think of it as separating the logic in two methods:
1) first one does initial stuff and then requests something via RPC
(in your example via myMethod() but with return type void)
2) second one is called by onSuccess() passing the results of the RPC
and continues with the requested data where first method "ends"

Hope it helps,

Andreas

[Sean]

Yeah, it takes a while to start thinking Asynchronously. But Andreas
has the right of it. You no longer think of it as call myMethod() to
return the ArrayList<String>; you have to think of it is:

1) What do I want my user to do to request the data. (Or my program,
like on start up you want the data).
Here is where you will call your service with the callback
object.

then

2) When I get this data, what do I want to do with it?
That is what you put in your onSuccess method.

Once you get the mentality down, it's extremely powerful and your web
pages will show it.

[day_trader]

Thanks for the replies thus far.

That all makes sense. I did have strong doubts about the likelihood of
what I wanted but as I am not an expert in the field I thought it was
better to make sure.

Actually, my problems would be solved quite quickly if I got around my
initial problem that led to this posting. Basically, there is a class
in my client side, under myApp.client.models.SomeModel that I need to
pass to the server. The problem is that the server cannot see this
class as I get an error when I try to compile it. My question is: How
do I check if the class is on my SERVER classpath?

Thanks :)

[Sunny]

Hi day_trader

As far as i can think is that you are trying to pass an object with
the data of the class..

now to make your class go to the server side all you need to do is to
move it to a package that is in the package that is *not* mentioned in
your <your_gwt_xml>.gwt.xml file as the classes in these
packages,which are mentioned in the gwt.xml file, get "ajaxified" and
sent on to the client.

Hope this helps.

Sunny.

[day_trader]

This is where I am rather confused. As when i move it to
a package which isn't named in the .gwt.xml file I receive
an error of "cannot be resolved to a type". Which is fair enough,
as I assumed everything in the .gwt.xml was putting the classes
in 'view' of everything in the application? Or perhaps I'm very
muddled up!

Sorry for the continued annoyance! I very much apologise.

Malcolm

[andreas]

You do not have to move something out of 'client' packages to have it
on your server. This is definitely wrong!

You do have to move classes you want to have on the client or both
client and server into the client packages (or declare those packages
in your *.gwt.xml files).

Since you want your class to be passed from the client to the server
this class definitely needs to be in your 'client' package. I don't
know why you get an error on compiling, maybe you can give more
informations on this one. GWT compiles all Java files (also those in
'client') to .class files in your war/WEB-INF/src/ folder so all
classes will be accessible on the server.

Andreas

[andreas]

Sorry, it's war/WEB-INF/classes/.

[day_trader]

It could possibly be because I am using Enunciate to develop my
application with. Here is my complete error:

[INFO]
------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO]
------------------------------------------------------------------------
[INFO] Problem assembling the enunciate app.

Embedded error: Class not found: TreeModel

I've just tried putting TreeModel into my gwt.xml file : <inherits
name='com.myApp.client.models.TreeModel'/> however this doesn't appear
to work either. I have posted this to the Enunciate Mailing List as
well, so hopefully one of those guys can enlighten me if it's a
probably with Enunciate and not GWT/GXT.

Malcolm

[day_trader]

Oops. That was supposed to say:

a 'PROBLEM' with...

[andreas]

The inherits tag is for inheriting GWT modules not for inheriting Java
files or similar (afaik).

You add packages to the GWT translatable sources via source tag:

<source path='client' />

This should be enough assuming your GWT module is in 'com.myApp'.

Andreas

[day_trader]

Does not appear to be working even with the <source path=''/>,
assuming I'm giving the correct path. Is the path of the form of a
directory or package?

[andreas]

http://lmgtfy.com/?q=gwt+module+xml+source

http://www.gwtapps.com/doc/html/com.google.gwt.doc.DeveloperGuide.Fundamentals.Modules.ModuleXml.html
http://www.gwtapps.com/doc/html/com.google.gwt.doc.DeveloperGuide.Fundamentals.Modules.html

It's a subpackage of the package your module is located in (your
*.gwt.xml).

Andreas

[day_trader]

I managed to find that after my last post. Whilst they were good links
it still does not seem to work. Something fundamental is wrong but I
can't work out what. I appreciate the help thus far but it appears I'm
in some eternal loop!