CAS 5.1 Database Authentication Issue

[Berry]

It's the first time I use CAS, and I aim for Database/LDAP Authentication.
I managed to make the static mode CAS server with https works. (gradle overlay template)
Then I tried to add the database authentication support, by adding

compile "org.apereo.cas:cas-server-support-jdbc:${project.'cas.version'}"
to the script file, and add the database connect information to the property file.
Accordding to the document, net.sourceforge.jtds.jdbc.Driver is available after the rebuild, but it turns out to be "ClassNotFound Exception".
So I just import the dependency manually:
compile group: 'net.sourceforge.jtds', name: 'jtds', version: '1.3.1'
I got a exception: "'principal' cannot be null".
I need a more detailed document to complete the configuration, or at least a typical property file.
In the "Database Authentication" section, all lines are with a leading #, I'm really confused and don't know what each key-value pair means.