Spring Boot – Could not open JPA EntityManager for transaction

If you are getting something like this

Request processing failed; nested exception is org.springframework.transaction.
CannotCreateTransactionException: Could not open JPA EntityManager for transaction; 
nested exception is org.hibernate.exception.JDBCConnectionException: 
Unable to acquire JDBC Connection] with root cause

java.net.ConnectException: Connection refused
	at java.base/sun.nio.ch.Net.pollConnect(Native Method) ~[na:na]
	at java.base/sun.nio.ch.Net.pollConnectNow(Net.java:589) ~[na:na]
	at java.base/sun.nio.ch.NioSocketImpl.timedFinishConnect(NioSocketImpl.java:542) ~[na:na]
	at java.base/sun.nio.ch.NioSocketImpl.connect(NioSocketImpl.java:597) ~[na:na]
	at java.base/java.net.SocksSocketImpl.connect(SocksSocketImpl.java:333) ~[na:na]
	at java.base/java.net.Socket.connect(Socket.java:648) ~[na:na]

before digging inside your Spring Boot configuration, make sure that Docker with your MySQL database is still running ;)