> For the complete documentation index, see [llms.txt](https://ondrej-kvasnovsky-2.gitbook.io/vaadin-on-grails-3/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ondrej-kvasnovsky-2.gitbook.io/vaadin-on-grails-3/chapter1/plugin_configuration/ui-class.md).

# UI class

Sample UI class `src/groovy/app/MyUI.groovy` which contains code that just shows a label in the web browser.

We can immediatelly start coding Vaadin application using that file, or maybe rather do a refactoring. For example, rename the file to `AppUI.groovy` and move it to different package (folder) `src/groovy/com/company/app`. Then you need to change `mapping` property inside `VaadinConfig.groovy`.