Adding java custom classes to Ignition 8.1

Using Eclipse, I wrote a simple class for update database, and exported the jar file, put file into lib/core/common folder.
I programmed a button script in the designer, and then can successfully call the class method, but it fail when execute “Class.forName(“com.mysql.jdbc.Driver”);” It seems that Driver cannot be found, but I have set CLASSPATH.
Where am I doing wrong?

JDBC drivers aren’t on the classpath in the Designer and Client.

That does it !!
Thanks for the help!