Is it possible to add GWT as a component in an already existing webpage?
Perhaps this is what you are looking for ?
Running a GWT application (including Applets) inside an IFRAME from an ASP.NET 3.5 app?
I think the answer on that question is relevant.
Yes, GWT can be added to any existing webpage. GWT's RootPanel will be the div you place on that webpage.
Hope this helps.
You need to understand the constraints of browser technology. Perhaps, you already do.
Setting up a communication channel
Componentization would require ability to communicate.
Let us say, you need to write your combo app using both jquery and GWT. Your jquery side should be able to dedicate a HTML element into which it could write. Like a simple DIV, ensuring that the element has an ID. You could have several elements for such a purpose.
On the GWT side, your GWT code would be able to grab these elements thro getElementById. Voila! There are your communication channels.
GWT is a dominating possessive creature, for one reason - it refuses to create widgets thro which you could name with an ID (except for ensuredebugId). For that reason, it does not fare very well running as a component.
More likely, your GWT app is the master and your non-GWT apps are the component.
All you need to do is to create a div in your existing web-page and give it an Id.
Then use the following to insert your component into that div.
RootPanel.get("PUT THE DIV ID HERE").setWidget(superCoolGwtComponent);