OBIEE XMLViewSerive.executeXMLQuery does not accept filters in ReportParams.filterExpressions

OBIEE version:

11.1.1.5.0

Symptom:

I need to evoke XMLViewService.executeXMLQuery() with different saved filters. I tried to set the filter in ReportParams.filterExpressions. The server returned the query result without any complaints. But the results were always the same as the result without any filters.

Work-around:

Set filters directly in ReportRef.