Java Development Tools

I'm testing JDeveloper 10.1.2 business components with mysql or postgresql because my company needs to connect also to these non-oracle DBs. ADF suits our developement needs, in speed and functionalities; anyway to make it our main developement system we need it to be compatible.

I made three tests and they were all disappointing.
At first, I installed MySQL 4.0 on my windows machine. I used the stable Connector/J 3.1
and then MySQL Connector/J 3.0, but in both cases JDeveloper had a strange behaviour: I can make the connection, I can navigate correctly through all tables in the connection-navigator, I see all the column names etc... Anyway, as I try to build a "new Entity Object" from a table, there are no available table properties, like if the table had no columns.
In this forum I only found documentation about rowid problems with mysql, but nothing about Entity Object wizard issues.

Then I switched to PostgreSQL. I installed it locally, so I had to choose the 8.01 since I'm on a windows machine. JDBC driver: postgresql-8.0-310 jdbc3
The developement test phase went ok, it is possible to use this DB just as if it was a Oracle, all the business components wizards works perfectly.
The problem is at runtime, unfortunately. I built a simple datapage on the struts-config diagram and I dragged on it a "read-only table" from the data control palette.
As I run the application, the embedded OC4J immediately returns this error:

oracle.jbo.JboException: JBO-29000: JBO-29000: JBO-29000: JBO-26061: Errore durante lapertura della connessione JDBC.
at oracle.jbo.JboException.<init>(JboException.java:343)
(...)
(in english: Error during JDBC connection)

There are no other available JDBC drivers for JVM 1.4x so I see no solution...
I also tried to connect to an older PostgresSQL with its (older) JDBC but I get same the result.

Anyone can help? Is it a JDev 10.1.2 issue?