Hello,

currently the autoGeneratedKeys() is supported in the most JDBC drivers like 

DB2: https://media.datadirect.com/download/docs/jdbc/alljdbc/help.html#page/jdbcconnect%2Fauto-generated-keys-support.html%23 
Oracle: https://media.datadirect.com/download/docs/jdbc/alljdbc/help.html#page/jdbcconnect%2FAuto-Generated_Keys_Support_4.html%23 
MySQL: https://media.datadirect.com/download/docs/jdbc/alljdbc/help.html#page/jdbcconnect%2FAuto-Generated_Keys_Support_3.html%23 
Sybase: https://media.datadirect.com/download/docs/jdbc/alljdbc/help.html#page/jdbcconnect%2FAuto-Generated_Keys_Support_6.html%23 
Informix: https://media.datadirect.com/download/docs/jdbc/alljdbc/help.html#page/jdbcconnect%2FAuto-Generated_Keys_Support_2.html%23 

Referring the User's Guide (jdbcug.pdf) downloaded from https://www.progress.com/jdbc/postgresql#documentation 
The flag 'Statement.RETURN_GENERATED_KEYS' indicating that any auto generated columns should be returned is defined into JDBC specification since version 3 and any JDBC API Compliance driver must support it

For PostgreSQL this is not implemented and we highly rely on driver to return values of auto-generated keys

Please refer to Case - 00474919 submitted to the Support

Best regards,

Nina