getting class not found exception for oracle jdbc driver in groovy script

I am using groovy scripting in soap ui 5.3.0 to connect oracle DB and  getting the below error while running the script?

java.lang.classNotFoundException:oracle.jdbc.driver.OracleDriver

import groovy.sql.*
com.eviware.soapui.support.GroovyUtils.registerJdbcDriver("net.sourceforge.jtds.jdbc.Driver")
def connstr = context.expand('${#Project#groovy_connstr}')
def dbuser = context.expand('${#Project#db_user}')
def dbpassword = context.expand('${#Project#db_password}')
def oracledriver = context.expand('${#Project#OracleDriver}')

def sql = Sql.newInstance(connstr, dbuser, dbpassword, oracledriver)
log.info "DB connection ready

I have placed ojdbc14 and ojdbc6-11.2.0.3 in soap ui/bin/ext folder. can anyone help me this?