JDBC with SQL Express

The java code :
  Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
   String connectionUrl = "jdbc:sqlserver://localhost:1433;" +     "instance=SQLEXPRESS;databaseName=UPM;integratedSecurity=true;";  Connection con = DriverManager.getConnection(connectionUrl);
returns "connection refused" no matter what I do.
 
I've used the surface config tool to enable TCP, I've added sqlsrvr.exe to the firewall exceptions, I've tried a dozen or so variations on the connection string.
I can connect to the database using the Management Studio.
 
Any ideas what I'm missing ????
Thanks.