PieChart

public class PieChartObject {
    private String category;
    private Integer value;

    public String getCategory() {
        return this.category;
    }

    public void setCategory(final String category) {
        this.category = category;
    }

    public Integer getValue() {
        return this.value;
    }

    public void setValue(final Integer value) {
        this.value = value;
    }
}

// Create model
final ChartModel model = ChartModel.New()
    .addColumn(Column.New(Type.STRING))
    .addColumn(Column.New(Type.NUMBER));

// Add items to model
model.addRow("Katze", 50);
model.addRow("Hund", 25);
model.addRow("Schlange", 25);

// Set data
this.pieChart.setModel(model);

final ChartModel model = ChartModel.New()
    .addColumn(Column.New(Type.STRING))
    .addColumn(Column.New(Type.NUMBER));

new ProductDAO().getProductsByCategoryForChart().forEach(p -> {
    model.addRow(p.getCategory().getCategoryname(), (int)p.getAmount());
});

chart.setModel(model);