Jag löste problemet enligt beskrivningen här:http://blog.netgloo.com/2015/07/09/spring-boot-communications-link-failure-with-mysql-and-hibernate/
, lägga till dessa konfigurationer i application.properties
fil:
spring.datasource.tomcat.testWhileIdle = true
spring.datasource.tomcat.timeBetweenEvictionRunsMillis = 60000
spring.datasource.tomcat.validationQuery = SELECT 1