Connect Grails to Autonomous ORACLE database

Question

I want to connect my grails server to an autonomous ORACLE database but when using the following configuration as dataSource:

dataSource {
            dbCreate = "none"
            driverClassName = "oracle.jdbc.OracleDriver"
            url = "jdbc:oracle:thin:@//tns_name?TNS_ADMIN=/home/wallet"
            username = "username"
            password = "password"
            schema = ""
            dialect = "com.flosslab.egrocery.dialect.Oracle10gDialectExtended"
            properties {
                ....
            }
        }

I keep receiving this error.

java.sql.SQLRecoverableException: IO Error: Unknown host specified

It works on sqplus when I put the wallet folder under $ORACLE_HOME/network/admin and then type sqlplus username/password@tns_name

Maybe I am missing something in the dataSource configuration ?