JDBC url for MySQL configuration to use utf8 character encoding

You may have to do with the following:

Changes in MySQL Connector/J 5.1.13 (2010-06-24)

• Connector/J did not support utf8mb4 for servers 5.5.2 and newer.

  Connector/J now auto-detects servers configured with character_set_server=utf8mb4 or treats the Java encoding utf-8 passed using characterEncoding=... as utf8mb4 in the SET NAMES= calls it makes when establishing the connection. (Bug #54175)