Jeevan, you are probably using an incompatible versions. There was a backwards incompatible change, so that you can’t currently use latest Spring Boot with latest Vaadin 10. Go with Spring Boot 2.0.2 for a while or use a snapshot version of Vaadin 10 (10.0-SNAPSHOT + vaadin snapshot repository). The compatibility fix for latest Vaadin should arrive soon.
cheers,
matti