How to import files while loading a groovy class?

I am loading a class and doing some sql select statements, it seems that import groovy.sql.Sql needs to be imported. How can I load some library while loading a class?

My code (works fine if I remove Sql operations)

def fClass = new GroovyClassLoader().parseClass( new File( 'plugin/Pi.groovy' ) )
 result=fClass.newInstance().buildTags( params, i9piparams, "userRoleCount")
 

pi.groovy

public class Pi{
     def result
 
     private def getDbUrl(dbdriver,dbhost,dbport,dbname)
     {
         return "$dbdriver:@$dbhost:$dbport:$dbname"
     }
 
     public def buildTags(Map<String,String> params,Map<String,String> i9piparams,def i9piType)
     {
 
         println params
         println i9piparams
 
         /*some Sql operation*/
         Driver="oracle.jdbc.driver.OracleDriver"
             dbdriver="jdbc:oracle:thin"
         def url=getDbUrl(dbdriver,params.tns,i9piparams.dbport,i9piparams.dbname)           
 
             def sql = Sql.newInstance(url,params.u,params.x,Driver)
 
             sql.eachRow("select name, value from v\$parameter where name = 'open_cursors'"){ row ->
                 result.name=row.name
                 result.value=row.value
             }
 
     }
 }
 

Output

[pd:admin, u:zx5531d, tns:foner, dh:abds, dn:D35531, dp:11531, un:admin, x:cx15531]
 [:, dbname:orcl, dbport:1521, dbtype:oracle]
 Exception in thread "main" groovy.lang.GroovyRuntimeException: Could not find matching constructor for: groovy.sql.Sql(org.codehaus.groovy.runtime.GStringImpl, groovy.util.slurpersupport.Attributes, java.lang.String, java.lang.String)
 .
 .
 .
 

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