You were directed to this help topic because your server code needed a class or
resource that was not found on the web app classpath, but was found
on the system classpath. The system classpath is the classpath
you specify when launching the Java VM to run hosted mode. The web app
classpath is different — it consists of classes that live in your web
application's war directory. All server classes and dependencies should
to be placed in your war directory: libraries (jars) should be placed in
war/WEB-INF/lib/
war/WEB-INF/classes/
GWT hosted mode helpfully works around this problem by mapping these outside resources into your web app classpath. This warning reminds you that failing to address the issue can lead to problems when you actually deploy your web app to a real server.
com.google.gwt.user.client.rpc.RemoteService
gwt-servlet.jar
from the GWT install directory
into your web app's war/WEB-INF/lib/
gwt.nowarn.webapp.classpath
-Dgwt.nowarn.webapp.classpath