SummaryType.render should return an Object

[rzschech]

The SummaryType method:

public abstract double render(Object v, ModelData m, String field, Map<String, Object> data)

should return an Object.

This allows for non-double based summaries like BigDecimal, max and min String or Date etc.


Also the implementations of SUM, AVG and COUNT should check for null values when going:

((Number) m.get(field)).doubleValue()

I would suggest use the same rules as SQL for nulls in SUM, AVG and COUNT.