1.3. Connecting Data

There are three ways how you can pass data to a chart: through the DataProvider interface, using the datasource mechanism, or the simplified data binding API, which allows adding the data directly using the addData() method and convenient MapDataItem constructors for those charts that are not bound to a datasource.

  • The DataProvider interface has a standard implementation: ListDataProvider class. It contains a list of DataItem instances from which the data for the chart will be taken. There are several standard implementations of DataItem interface:

    • EntityDataItem takes an instance of any entity.

    • MapDataItem is a set of key-value pairs.

    • SimpleDataItem takes an instance of any public class.

An instance of DataProvider is passed to the setDataProvider() method of chart configuration. This approach to providing chart data is the most universal, but it requires creating instances of DataProvider and DataItem in a screen controller.

  • A CollectionDatasource type datasource can be assigned to a Chart component by invoking the setDatasource() method. This approach requires an entity that will represent chart data. It may be convenient when such entity already exists in the application data model and also when chart data should be displayed as a table.

Example of Working with Charts illustrates all three approaches to providing chart data.

Entity properties or the values contained in an instance of DataProvider which are used for display purposes are defined in the chart attributes. The set of chart attributes may differ for different chart types. For example, for the chart:pieChart component, you should define the valueField and titleField attributes. The following types are allowed for attribute values: Integer, Long, Double, String, Boolean, Date.

Dynamic addition of data to an existing chart is supported for both the datasource and the data provider mechanisms.