Pentaho ChartBeans
In this article, the Pentaho ChartBeans project is introduced. Pentaho ChartBeans is a wrapper around other chart engines (such as JFreeChart and Open Flash Chart). By wrapping these "chart engines," a single way of expressing charts has been created.
Prerequisites
Charting Terminology
To eliminate confusion in documentation, the Pentaho ChartBeans project has documented its preferred charting terminology. In addition to standardizing on terms for the purpose of the Pentaho ChartBeans project, this terminology page provides an excellent introduction to charting in general. Please review this page before proceeding.
ChartBeans
Pentaho ChartBeans requires three inputs: the data to be charted, the structure of the chart, and the styling of the chart.
Chart Data
The org.pentaho.chart.ChartData interface is the format for data that is passed to Pentaho ChartBeans. ChartData extends javax.swing.table.TableModel to add row, column, and cell metadata. For example, ChartData allows you to set row and column names. Row and column names are useful for giving meaningful names to series and categories. A single implementation, org.pentaho.chart.data.ChartTableModel, is provided.
Chart Document
The org.pentaho.chart.core.ChartDocument class is a Java representation of a Pentaho ChartBeans XML document. It is a tree of org.pentaho.chart.core.ChartElement instances. A chart document includes elements like title, series, and plot.
Chart CSS
Pentaho ChartBeans uses Cascading Style Sheets (CSS) to style charts. Pentaho ChartBeans is not limited to the W3C's style attributes (although it attempts to use them where appropriate, for familiarity). By using CSS, Pentaho ChartBeans allows you to completely separate chart structure and style. You can use external style sheets, inline selectors, as well as class and style attributes. Using an external style sheet would allow an organization to create a consistent look to all of its charts.
Example
Chart Data
private static ChartTableModel createChartTableModel() {
Object[][] dataArray = { { 5.55, 10.11, 20.22 }, { 30.33, 40.44, 50.55 }, { 31.33, 99.44, 150.55 },
{ 32.33, 1.44, 30.55 }, { 34.33, 88.44, 77.55 }, { 35.33, 22.44, 54.55 }, { 36.33, 33.44, 52.55 },
{ 37.33, 76.44, 54.55 }, { 38.33, 7.44, 59.55 }, { 39.33, 48.44, 56.55 }, { 40.33, 19.44, 57.55 },
{ 50.33, 104.44, 36.55 }, { 60.33, 23.44, 74.55 }, { 20.33, 90.44, 80.55 }, { 60.33, 18.44, 27.55 },
{ 10.33, 22.44, 97.55 }, { 20.33, 59.44, 55.55 }, { 90.33, 140.44, 22.55 }, { 100.33, 56.44, 76.55 },
{ 40.33, 50.44, 50.55 }, { 60.66, 70.77, 80.88 } };
ChartTableModel data = new ChartTableModel();
data.setData(dataArray);
// give names to the categories
data.setColumnName(0, "budget");
data.setColumnName(1, "sales");
data.setColumnName(2, "forecast");
// give names to the series
final String ROW_NAME_KEY = "row-name";
data.setRowMetadata(0, ROW_NAME_KEY, "1");
data.setRowMetadata(1, ROW_NAME_KEY, "2");
// ----- lines omitted -----
data.setRowMetadata(20, ROW_NAME_KEY, "21");
return data;
}
Chart Document
<chart xmlns="http://reporting.pentaho.org/namespaces/charting/1.0">
<!-- external style sheet -->
<stylesheet href="theme.css" />
<!-- chart title -->
<title>Bar Chart Using Pentaho ChartBeans</title>
<!-- styling on individual series using style and class attributes -->
<series style="-x-pentaho-chart-series-type: bar; -x-pentaho-chart-bar-style: bar;" class="series1" />
<series class="series2" />
<!-- lines omitted -->
<series class="series18" />
<!-- wrap colors because there are more series than colors in the theme -->
<series class="series1" />
<series class="series2" />
<series class="series3" />
<!-- styling on plot using style attribute -->
<plot style="-x-pentaho-chart-orientation: horizontal"/>
</chart>
Troubleshooting
What can go wrong? Cover common and known problems, then cover how you can discover the root of a problem (logging, debugging symbols, etc.)