---
title: Troubleshooting
order: 6
layout: page
---

[[addons.troubleshooting]]
= Troubleshooting

If you experience problems with using add-ons, you can try the following:

* Check the [filename]#.gwt.xml# descriptor file under the the project root
package. For example, if the project root package is
[filename]#com.example.myproject#, the widget set definition file is typically
at [filename]#com/example/project/AppWidgetset.gwt.xml#. The location is not
fixed and it can be elsewhere, as long as references to it match. See
<<../clientside/clientside-module#clientside.module,"Client-Side
Module Descriptor">> for details on the contents of the client-side module
descriptor, which is used to define a widget set.

* Check the [filename]#WEB-INF/web.xml# deployment descriptor and see that the
servlet for your UI has a widget set parameter, such as the following:


+
----
<init-param>
  <description>UI widgetset</description>
  <param-name>widgetset</param-name>
  <param-value>com.example.project.AppWidgetSet</param-value>
</init-param>
----
+
Check that the widget set class corresponds with the [filename]#.gwt.xml# file
in the source tree.

* See the [filename]#VAADIN/widgetsets# directory and check that the widget set
appears there. You can remove it and recompile the widget set to see that the
compilation works properly.

* Use the [guilabel]#Net# tab in Firebug to check that the widget set (and theme)
is loaded properly.

* Use the ?debug parameter for the application to open the debug window and check
if there is any version conflict between the widget set and the Vaadin library,
or the themes. See
<<../advanced/advanced-debug#advanced.debug,"Debug Mode
and Window">> for details.

* Refresh and recompile the project. In Eclipse, select the project and press F5,
stop the server, clean the server temporary directories, and restart it.

* Check the Error Log view in Eclipse (or in the IDE you use).