To clarify, there are two separate, distinct ways to access the DSAPI:
From your last comments, it looks like you are referencing the documentation for both, which would explain any confusion. If you are integrating with Voyence using Java, I would recommend using the RMI interface just to keep everything in the Java ecosystem.
Connecting to the DSAPI's RMI interface is simple. If you have connected to the VoyenceControl API using the J2EE interface before, you are 99% there! The method of connecting to the VoyenceControl API J2EE interface is identical to connecting to the DSAPI RMI interface with one small exception: when you make the context.lookup("...") call, use the DataApiService.JNDI_NAME field like this:
Context context = ... // See the DSAPI RMI samples for retrieving the context. There is a standard way. Also, this is the same context used for connecting to the VoyenceControl API (J2EE)
DataApiService dsapi = (DataApiService) context.lookup(DataApiService.JNDI_NAME);
... // make your calls to the DSAPI
If you haven't already seen the "Overview" javadoc page, take a look. It gives a full description of how to connect to the two different API interfaces.
Don't forget to look at the samples for some easy cut-and-paste boilerplate code to save you some time and trouble.
If you still have trouble, I'm here to help