Caused by: java.lang.NoClassDefFoundError: com/vaadin/v7/ui/Upload$Receiver

[tstsogoo]

vaadin 8.4.3

[mstahv]

The module appears to be needing the v4 compatibility package at least with the UploadField component. So add this to your pom file and it should work:

<dependency>
  <groupId>com.vaadin</groupId>
  <artifactId>vaadin-compatibility-server</artifactId>
  <version>8.0.0</version>
</dependency>