To get an instance of the ReportEngine, you can use the method getInstance() or getInstance(boolean setDebugLevel) in the jet.server.api.engine.ReportEngineFactory.
For example,
bean = ReportEngineFactory.getInstance();
or,
bean = ReportEngineFactory.getInstance(true);
Reference: See JReport Javadoc in <install_root>\help\api
for usage of the ReportEngine methods.