Hi,
Got this defenition from Wikipedia:-
A database trigger is procedural code that is automatically executed in response to certain events on a particular table in a database. Triggers can restrict access to specific data, perform logging, or audit data modifications.
It clearly states that triggers are setup on the database to perform certain steps when a particular event occurs on the database. A trigger can be executed on the database if a JDBC program performs any action that has been declared to 'trigger' it.
Does this answer your doubt?
Cheers,
Raj.