//hsqldb.properties must be in WEB_INF/classes dir for this style loading
getClass().classLoader.getResource('hsqldb.properties').withReader {
    System.properties.load it
}
arg = 'dsn user pass drv'.split().collect {
    System.properties."hsqldb.$it"
}
db = Sql.newInstance(*arg)

groovlet_hsqldb_properties

Example of using .properties file for get database connection parameters into script

Load HSQLDB connection parameters from .properties file in groovlet

Groovy