Iam trying to retreive the changesets associated with a workitem.This is my code.

public class get_changesets {

    private List<IChangeSet> getChangeSets(IWorkItem wi)
            throws TeamRepositoryException {
       
        IRepositoryItemService repositoryItemService = getService(IRepositoryItemService.class);

        ILinkService linkService = getService(ILinkService.class);
        ILinkServiceLibrary linkLibrary = (ILinkServiceLibrary) linkService
                .getServiceLibrary(ILinkService.class);
        IItemReference workItemRef = IReferenceFactory.INSTANCE
                .createReferenceToItem(wi);
        ILinkQueryPage linkPage = linkLibrary.findLinks(
                WorkItemLinkTypes.CHANGE_SET, workItemRef);

        List<IChangeSet> changeSets = new ArrayList<IChangeSet>();

        for (ILink link : linkPage.getAllLinksFromHereOn()) {
            // Change set links should be item references
            IChangeSetHandle changeSetHandle = (IChangeSetHandle) link
                    .getSourceRef().resolve();
            IChangeSet changeSet = (IChangeSet) repositoryItemService
                    .fetchItem(changeSetHandle, IRepositoryItemService.COMPLETE);
            changeSets.add(changeSet);
        }
        return changeSets;
    }
}

what are the server side classes for "IRepositoryItemService", "ILinkServiceLibrary" , " getService()" method?
How do I access the server side API's of RTC server?