Roo+Hibernate+MySQL => Problem with UTF8 special chars

Scenario:
simple entity with a String field plus according Control.

If you enter e.g. german special chars like "München" or "Hänsel" into the form field (no matter whether this is a update or create) and save the data, the value get's stored as "M?chen" or "H?sel" into the MySQL-Database. I searched for this issue and found some tipps at the following blogs.

http://www.it-blogger.com/2005-08-13/mysql-hibernate-und-utf8/
http://twilia.blogspot.com/2007/09/hibernate-mit-mysql-und-utf8.html

I tested their suggestions by adding some parameters to the database.properties "database.url" entry. It currently looks the following:
database.url=jdbc\:mysql\://localhost\:3306/my_utf_test?autoReconnect\=true&useUnicode\=true&characterEncoding\=UTF-8

I even tried to enter the url into the persistence.xml (see below) but neither of these things worked.
<property name="hibernate.connection.url" value="jdbc:mysql://localhost/my_utf_test?useUnicode=true&characterEncoding=utf8&connectionCollation=utf8_general_ci&characterSetResults=utf8" />

This bug makes ROO+Hibernate actually unusable for german based applications for me at the moment.

Have you got any suggestions?

Greets,
Alex