Profium, Asemantics and HP Laboratories initiate SPARQL4J open source effort "Profium, Asemantics and HP Laboratories have initiated an open source effort to provide Java programmers with a JDBC driver to access SPARQL-enabled metadata repositories."
SPARQL4J SF project.
A standard driver would be a great thing. Modelling RDF queries in SPARQL doesn't seem accurate using JDBC.
A JDBC driver seems doesn't really seem like the appropriate interface to support - there's a lot of data types in a JDBC driver that just aren't supported in SPARQL and probably won't be. RDF just has a different way of handling datatypes. Also, you have to use things java.sql.ResultSet, java.sql.Connection, java.sql.SQLException etc. Does it make sense to send a SPARQL query and receive an SQLException? Even other APIs built on SQL databases like Hibernate's Query Language and JDO's Query Language (or Using JDO 2.0: JDOQL) use their own APIs. XML databases have XMLDB.
Maybe having a look at some of the JDBC 4.0 which has things like XML datatype support but it's still "working with relational SQL data stores from the Java platform".