MySQL with JPA: Illegal mix of collations (utf8mb4_general_ci,IMPLICIT) and (utf8_general_ci,COERCIBLE)

Question

I need to be able to store characters like \\xF0\\x9F\\x94\\xA5 in my database, which, according to this post need UTF8mb4 encoding.

So I

Answer 1

You do not need any change in the Java side, as utf8mb4 is just UTF-8 in Java.

Instead, as you can see here:

show variables WHERE variable_name like "col%";
+----------------------+------------------+
| Variable_name        | Value            |
+----------------------+------------------+
| collation_connection | utf8_general_ci  |
| collation_database   | utf32_general_ci |
| collation_server     | utf8_general_ci  |
+----------------------+------------------+

your connection setting is still utf8_general_ci; to set it at the connection level, one option is to execute the (mysql specific) query:

SET NAMES='utf8mb4'

before any attempt to use the utf8mb4 collation; or, generally for the mysql server, in /etc/my.cnf:

[mysql]
default-character-set = utf8mb4

[mysqld]
character-set-server = utf8mb4
collation-server = utf8mb4_unicode_ci

Another option without changing the connection string, is using a jdbc driver version >= 5.1.13: http://www.opensubscriber.com/message/java@lists.mysql.com/14151747.html