When working with Spring boot 2.1.x this warning message appears when starting up the application.
As indicated here, maybe this problem didn't show up in earlier versions because the related property was set to true by default and now it is false:
https://github.com/spring-projects/spring-boot/issues/12007
In consequence, solving this is as simple as adding the following property to the spring application.property file.
spring.jpa.properties.hibernate.jdbc.lob.non_contextual_creation = true