GWT Warning “Non-canonical source package”

The Problem

Sometimes you might want to include classes from a package in your gwt module, which are not in a sub-package of the package in which you have defined the Gwt module (MyModule.gwt.xml).

For instance, you might have the following directory structure:

/client/ClientService.java

/browser/BrowserEntryPoint.java

/browser/MyModule.gwt.xml

The first natural option would be to define a source dependency in the Gwt module (gwt.xml) as follows:

However, when compiling the module, a “Non-canonical source package” warning is issued. Furthermore, the class in the client package will not be recognized by the Gwt compiler.

The Solution

One clean (but not necessary straightforward) solution is to define a new Gwt module in the client package, and link this in your original module. The directory structure would change to:

/client/ClientService.java

/client/ClientModule.gwt.xml

/browser/BrowserEntryPoint.java

/browser/MyModule.gwt.xml

The following dependency would have to be added to MyModule.gwt.xml:

Resources

GWT Google Group – Source-Source

2 thoughts on “GWT Warning “Non-canonical source package””

and how does the ClientModule.gwt.xml looks like?

Max Rohde says:

May 23, 2013 at 9:02 am

ClientModule.gwt.xml can just be a default module definition such as:

<module rename-to="ClientModule">
<inherits name="com.google.gwt.user.User" />
<entry-point class="client.DummyEntryPoint" />
</module>

(please note you might need to add inherits as well)

Hope this helps.

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