Find if an SQLException was thrown because of a duplicate

You could "train" the program on startup (or config) by inserting a known duplicate key, and recording the thrown error code.

With basic JDBC, there really isn't a way to do what you are saying in a cross-database manner. As you mentioned getErrorCode could be used, but required vendor-specific error codes.

The only three ways I see to get around this is:

1. Use some sort of framework that does all of the translating from error code to meaningful exceptions (Hibernate would probably do this, someone else mentioned that Spring does)
2. Check for the duplicate manually (with a select) prior to doing your insert. (This wouldn't be 100%, as its technically possible that someone could have done an insert after your query).
3. After you get any sql exception on the insert, try to query for that id. If you can actually find the match - you can be fairly sure that the error you received was due to a duplicate primary key. (Although its possible that there was multiple problems, and that wasn't actually the one that was thrown).

My recommendation would be to write your code to avoid the problem as much as possible, and then (if absolutely necessary), use #3.

This is exactly what SQLException.getSQLState() is for. Acoording to Google, "23000" indicates a unique constraint violation in at least MySQL, PostgreSQL, and Oracle.