Could not open Hibernate Session for transaction
This problem happens when the connection to the database is disconnected or was not created at all by the application, but pool assumes connection is established.
Remedy for this could be checking credential to the database [username, password, host, port] and also checking the connection object before proceeding to database tasks like reading or updating.
Adding Unicode character to mysql from Java-hibernate
Invocation of init method failed – hibernate exception of caching