I did find a solution that gets me farther. The dbschema has a number of jars that it needs to access the Cassandra database. If I include all these files, then I can access the database. One simple solution was to add all the jars (I put them into a directory 'cassandra' where the other jars were) into the CLASSPATH in the logstash.bat file:
for %%i in ("%LS_HOME%\logstash-core\lib\jars\cassandra*.jar") do (
call :concat "%%i"
)
I can now access Cassandra.