Servlet Mappings, GWT Modules, and web.xml

GWT modules may declare one or more <servlet> tags. These define Java Servlets that implement the server-side component of a GWT-enabled web application.

In modern GWT applications, these are only used for testing, and it is discouraged to use them in application code.

During hosted mode startup, the set of expected servlets (from GWT module <servlet> tags) is validated against the set of actual servlets (from the WEB-INF/web.xml) and a warning is issued for each expected servlet which does not match an actual servlet.