This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
OK, we are sure that your DB is accessible from the code.
You gave us the exception:
org.springframework.transaction.CannotCreateTransactionException : Could not open JPA EntityManager for transaction; nested exception is javax.persistence.PersistenceException: org.hibernate.exception.GenericJDBCException: Cannot open connection
Please paste the full stack trace despite the fact that it can be very long.