Vaadin “A connector with id xy is already registered”

Question

Somewhere in my Vaadin application, I\'m getting this exception as soon as I connect using a second browser

Caused by: java.lang.RuntimeException: A connector

Answer 1

By running your application in debug mode (add ?debug at the end of URL in browser) you will be able to browse to the component, e.g:

-UIConnector(0)
--VerticalLayoutConnector(1)
---...
---LabelConnector(22)

where 22 is id from your stack trace. Find this component in your code and make sure that it is not static (yes, I saw such examples).