In the class JDBCAccessLogValve is an example for an table to hold access log values. In this table is a column ts which is defined as not null. This will only work on MySQL, because this value is never written by the Valve and other databases will complain about a column which is not filled with a value.
Javadoc corrected in SVN. The change will be in 5.5.21 onwards. Thanks for the report.