moving classes in shared folder into external library

Hi,

I am currently moving code out of my projects into reusable libraries.

There is one library for general Java/sever-side code, and there is a
library for gwt stuff.

The library for gwt stuff is a simple eclipse project with the following
gwt.xml-file:

<module>
<inherits name='com.google.gwt.user.User'/>
<inherits name="com.google.gwt.logging.Logging"/>
<set-property name="gwt.logging.popupHandler" value="DISABLED" />
<source path='mylib'/>
<stylesheet src="mylib.css"/>
</module>

At the moment, this library only contains classes, which were in the
project's "client" folder.
But I also want to move classes from the "shared" folder into this library.

- Where do I have to move the shared classes within my library and how
do these folders have to be declared in the gwt.xml file?
- How does it work, using a shared folder for both client and server
side code?
Does the same code be compiled twice, once by a traditional java
compiler and once by the GWT compiler?
What's the mechanism behind this "shared" folder concept?

Thanks
Magnus