When a user logs in to the (linux/unix) system as a user and runs a 4GL or ESQL/C program, the program can connect to a DB as the system account user without entering a password. e.g. If I login as rob and run a program it can connect to a DB without providing a password, providing rob has connect permission.
I would like to do a similar thing with a local java program that uses JDBC to talk to the DB server. Is this possible?
Yes, this is fully supported in the JDBC driver for Informix. You can connect without a password as the user who started the Java process that is on the same machine as the Informix server.
As Luis notes in his comment, you forego the username and password fields in your JDBC URL for this to work.