Configure wallet location in sqlnet.ora and listener.ora

I have a host containing multiple DBs and the connection to the DBs need to be SSL enabled. Since each DB has a unique wallet, I specify the wallet location in sqlnet.ora as: WALLET_LOCATION=(SOURCE=(METHOD=FILE)(METHOD_DATA=(DIRECTORY=wallet_folder/$ORACLE_UNQNAME))) This way the listener can use the correct wallet depending on the value of ORACLE_UNQNAME variable. But I have two issues with this method. 1. Since ORACLE_UNQNAME is a shell environment variable a client has no control over it. 2. Even when connecting from the same machine I have to bounce the listener after exporting ORACLE_UNQNAME value. What is the solution for such a scenario ?