Retrieve channel information in PI71 from web servlet

We have a servlet which works fine in 7.0 now i want to deploy it on 7.1 .

This servlet reads some parameters from a Channel and writes a report.

CPAFactory cpaFactory = CPAFactory.getInstance();

CPALookupManager lookup =cpaFactory.getLookupManager();

LinkedList list = lookup.getChannelsByAdapterType("RFC","http://sap.com/xi/XI/System");

in 7.1 the method lookup.getChannelsByAdapterType("RFC","http://sap.com/xi/XI/System"); allways retruns a empty list.

Do i have to add some spezial references in application-j2ee-engine or how to get the list of channels via web servlet?

plz help.

thx