public Dataset getDataset() throws DatasetProduceException {
Assert.check(producer != null, "you need to specifiy a producer for the data of the chart.");
if (data == null) {
data = (Dataset) producer.produceDataset(datasetProductionParams);
DatasetProductionTimeStore dataCache = DatasetProductionTimeStore.getInstance();
dataCache.addEntry(producer.getProducerId(), datasetProductionParams, new Date(datasetProduceTime));
}
Assert.check(data != null, "your producer of type " + producer.getClass().getName() + " produced a null dataset.");
return data;
}