As we all know, string encoding is fun and pleasant.

If your MySQL database uses the UTF-8 charset, you’ll probably want JRuby to use UTF-8. To start JRuby (or anything else on the JVM) with UTF-8 as the default encoding:

export JAVA_TOOL_OPTIONS='-Dfile.encoding=UTF-8'

We can test this, in jirb:

>> "".encoding
=> #<Encoding:UTF-8>

Now we can configure JDBC to connect with the proper encoding:

sql_server = 'jdbc:mysql://my_host/my_database?useUnicode=yes&characterEncoding=UTF-8'
DB = Sequel.connect(sql_server, ...)