Cewolf has a caching mechanism built in which prevents that charts have to be generated over and over again. So if you use the same parameters for the same datasetproducer to generate the chart cewolf uses a cached instance.
To avoid this you have to implement the DatasetProducer interface accordingly. Please refer to it's javadoc under http://cewolf.sourceforge.net/apidoc/de/laures/cewolf/DatasetProducer.html.
Regards,
Guido Laures
Project Lead Cewolf