Have you tried SQL Server Management Studio Express?
You can access SQL Server Compact 3.5 databases stored on a smart device or on the desktop computer by using SQL Server Management Studio in SQL Server or SQL Server Management Studio Express (SSMSE). http://technet.microsoft.com/en-us/library/ms172037.aspx
As for the JDBC Driver, you could take a look at this one, provided by Microsoft. I don't know if it works with the Compact Edition or if you already tried it, but I thought it was worth mentioning.