Serialize Point.y when null

Objective: generate a graph with one line series where
* point markers are not shown by default (only on hover)
* there are points with no data
* isolated points have their marker displayed, otherwise they would not be 
visible

Highcharts' wise, this means:
* specifying on the series or chart `marker: { enabled: false, states: { hover: 
{ enabled: true } } }`
* setting null y on points with no data
* setting `marker: { enabled: true }` on isolated point

See this fiddle: http://jsfiddle.net/J99MA/
This other fiddle is with using complete points instead of defining categories 
on xAxis: http://jsfiddle.net/J99MA/1/
When `y: null` is omitted, Highcharts will then not be able to draw the series 
as a line or spline series, and will draw it as a scatter plot (i.e. with no 
point connection).

With wicked-charts' implementation, setting null y on points with no data can 
be done with using `CoordinateSeries` or even `SimpleSeries`. However as we 
need to be able to set the `marker` attribute on points, we need to use 
`PointSeries` (unless I missed something).

However, with PointSeries, we can't specify `y: null` as Point has no specific 
Serializer and thus uses the default of suppressing null when serializing.

To circumvent the problem I overloaded the Point class in my project to add 
`@JsonInclude(value = JsonInclude.Include.ALWAYS)` on the `y` attribute, but 
that doesn't feel right.

Note: this is with wicked-charts 1.5.0 for wicket 1.5 
(wicked-charts-wicket15:1.5.0).

Original issue reported on code.google.com by sebastie...@gmail.com on 9 Apr 2014 at 8:24

kurtomerfaruk / wicked-charts

Serialize Point.y when null #66