/*
 * Setting TNS_ADMIN to point to the locatioon of the tnsnames.ora file and/or the
 * property files (e.g., ojdbc.properties, new with DB18c)
 * by default $ORACLE_HOME/network/admin but you must explicly set its value
 *
 *
 *
 * option 1 -- non-intrusive
 */
  java -Doracle.net.tns_admin=<location of tnsnames.ora>
/*
 * option 2 -- intrusive
 */

System.setProperty("oracle.net.tns_admin", <location of tnsnames.ora>);
/*
 * option 3 -- intrusive, in JDBC URL (requires DB18c or later)
 */
jdbc:oracle:thin:@<alias>?TNS_ADMIN=<location of tnsnames.ora>