charts Charts Sample Shows how the chart element could be used to render different types of charts. How to render different types of charts using the built-in chart element. 1.0.0 Sanda Zaharia shertage@users.sourceforge.net Charts in JasperReports

The JasperReports library does not produce charts and graphics itself. However, it can easily integrate charts, barcodes, and graphics produced by other more specialized Java libraries.
The great majority of available Java libraries that produce charts and graphics can output to image files or in-memory Java image objects. And such image objects can be integrated into a JasperReports document using a normal image element.
To simplify the integration of charts inside reports, JasperReports provides a specialized <chart> element.

Chart Properties

When including and configuring a chart component, three entities are involved:
  • The overall chart component
  • The chart dataset (which groups chart data–related settings)
  • The chart plot (which groups visual settings related to the way the chart items are rendered)
JasperReports currently supports the following types of charts: Pie, Pie 3D, Bar, Bar 3D, XY Bar, Stacked Bar, Stacked Bar 3D, Line, XY Line, Area, XY Area, Stacked Area, Scatter, Bubble, Time Series, High-Low-Open-Close, Candlestick, Multiple Axis, Meter, Thermometer and Gantt.
All chart types have a common set of properties. Charts are normal report elements, so they share some of their properties with all the other report elements. Charts are also box elements and can have hyperlinks associated with them.
Chart-specific settings that apply to all types of charts are grouped under a special JRXML tag called <chart>. It contains the following elements:
  • <reportElement />
  • <box />
  • <chartTitle />
  • <chartSubtitle />
  • <chartLegend />
  • <anchorNameExpression />
  • <hyperlinkReferenceExpression />
  • <hyperlinkAnchorExpression />
  • <hyperlinkPageExpression />
  • <hyperlinkTooltipExpression />
  • <hyperlinkParameter />
Attributes available for all chart types are:
  • isShowLegend - indicates whether the legend will be rendered visible
  • evaluationTime - indicates the moment when chart goes rendered. Default value is Now
  • evaluationGroup - used to specify the group at which to render the chart, when evaluationTime is Group
  • hyperlinkType - indicates the type of the hyperlink element.
  • hyperlinkTarget - indicates the target of the hyperlink.
  • bookmarkLevel - the level of the bookmark corresponding to the anchor.
  • customizerClass - the name of the chart customizer class.
  • renderType - represents the specified format used to render the chart.
  • theme - the name of the chart theme used to draw the chart.

Chart Rendering

In generated reports, the output produced by a chart element is an image element. Image elements are drawn using implementations of the JRRenderable interface. Charts have an attribute called renderType which specifies the renderer implementation that will be used to render the chart during export or report display. By default, JasperReports recognizes the following values for this attribute:
  • draw - the chart is drawn directly on the target graphic context using the JFreeChart API.
  • image - an image is first produced from the chart and this image in turn gets rendered onto the target graphic context.
  • svg - the chart is transformed into the Scalable Vector Graphics format and from that format is then rendered onto the target graphic context.

Chart Title, Subtitle and Legend

All charts can have one title and one subtitle. All chart types can display a legend that explains the values represented by the chart. By default all charts display the legend, but one can suppress this display by setting the isShowLegend flag to false.
Chart titles, subtitles and legends are optional and can be customized for color, font, and position. They can be placed at the top of the chart, at the bottom of the chart, or on the left or right side of the chart, depending on the value of the position attribute.

Chart Datasets

Charts rely on a data-oriented component called the chart dataset for mapping report data and retrieving chart data at runtime.
A chart dataset is an entity which can get initialized and incremented at specified moments during the report-filling process and iteration through the report data source. Like a report variable, at any moment a chart dataset holds a certain value, which is a complex data structure that gets incremented and will be used for rendering the chart at the appropriate moment.
Several types of chart datasets are available in JasperReports because each type of chart works with certain datasets: Pie, Category, XY, Time Series, Time Period, XYZ, High-Low, Value and Gantt.
The JasperReports object model uses the JRChartDataset interface to define chart datasets. There are implementations of this interface for each of the aforementioned dataset types. All chart datasets initialize and increment in the same way, and differ only in the type of data or data series they map. The increment or reset type and increment or reset groups can be specified by setting the dataset common attributes below:
  • resetType
  • resetGroup
  • incrementType
  • incrementGroup
Specific dataset types are:

Pie Dataset

A pie dataset is characterized by the following expressions:
  • <keyExpression /> - represent the categories that will make up the slices in the pie chart. This expression can return any java.lang.Comparable object.
  • <valueExpression /> - produces the values that correspond to each category/key in the dataset. Values are always java.lang.Number objects.
  • <labelExpression /> - if this expression is missing, the chart will display default labels for each slice in the pie chart. Use this expression, which returns java.lang.String values, to customize the item labels for the pie chart.
  • <sectionHyperlink /> - sets hyperlinks associated with pie sections

Category Dataset

A category dataset is characterized by the <categorySeries /> element, which contains:
  • <seriesExpression /> - indicates the name of the series. This expression can return any java.lang.Comparable object.
  • <categoryExpression /> - returns the name of the category for each value inside the series specified by the series expression. Categories are java.lang.Comparable objects.
  • <valueExpression /> - produces the values that correspond to each category in the dataset. Values are always java.lang.Number objects.
  • <labelExpression /> - if this expression is missing, the chart will display default labels for each item in the chart. Use this expression, which returns java.lang.String values, to customize the item labels for the chart.
  • <itemHyperlink /> - sets hyperlinks associated with chart items

XY Dataset

An XY dataset is characterized by the <xySeries /> element, which contains:
  • <seriesExpression /> - indicates the name of the series. This expression can return any java.lang.Comparable object.
  • <xValueExpression /> - returns the java.lang.Number value representing the X value from the (x, y) pair that will be added to the current data series.
  • <yValueExpression /> - returns the java.lang.Number value representing the Y value from the (x, y) pair that will be added to the current data series.
  • <labelExpression /> - if this expression is missing, the chart will display default labels for each item in the chart. Use this expression, which returns java.lang.String values, to customize the item labels for the chart.
  • <itemHyperlink /> - sets hyperlinks associated with chart items

XYZ Dataset

An XYZ dataset is characterized by the <xyzSeries /> element, which contains:
  • <seriesExpression /> - indicates the name of the series. This expression can return any java.lang.Comparable object.
  • <xValueExpression /> - returns the java.lang.Number value representing the X value from the (x, y, z) item that will be added to the current data series.
  • <yValueExpression /> - returns the java.lang.Number value representing the Y value from the (x, y, z) item that will be added to the current data series.
  • <zValueExpression /> - returns the java.lang.Number value representing the Z value from the (x, y, z) item that will be added to the current data series.
  • <labelExpression /> - if this expression is missing, the chart will display default labels for each item in the chart. Use this expression, which returns java.lang.String values, to customize the item labels for the chart.
  • <itemHyperlink /> - sets hyperlinks associated with chart items

Time Series Dataset

A time series dataset is characterized by the timePeriod attribute, and the <timeSeries /> element.
The timePeriod attribute specifies the type of the data series inside the dataset. Time series can contain numeric values associated with days, months, years, or other predefined time periods. Possible values are:
  • Year
  • Quarter
  • Month
  • Week
  • Day - this is the default value
  • Hour
  • Minute
  • Second
  • Millisecond
The <timeSeries /> element contains:
  • <seriesExpression /> - indicates the name of the series. This expression can return any java.lang.Comparable object.
  • <timePeriodExpression /> - returns a java.util.Date value from which the engine will extract the corresponding time period depending on the value set for the timePeriod attribute mentioned above.
  • <valueExpression /> - returns the java.lang.Number value to associate with the corresponding time period value when incrementing the current series of the dataset.
  • <labelExpression /> - if this expression is missing, the chart will display default labels for each item in the chart. Use this expression, which returns java.lang.String values, to customize the item labels for the chart.
  • <itemHyperlink /> - sets hyperlinks associated with chart items

Time Period Dataset

An time period dataset is characterized by the <timePeriodSeries /> element which contains:
  • <seriesExpression /> - indicates the name of the series. This expression can return any java.lang.Comparable object.
  • <startDateExpression /> - specifies the beginning of the date interval with which the numeric value will be associated when it is added to the time period series.
  • <endDateExpression /> - specifies the end of the date interval with which the numeric value will be associated when it is added to the time period series.
  • <valueExpression /> - returns the java.lang.Number value to associate with the current date interval specified by the start date and end date expressions.
  • <labelExpression /> - if this expression is missing, the chart will display default labels for each item in the chart. Use this expression, which returns java.lang.String values, to customize the item labels for the chart.
  • <itemHyperlink /> - sets hyperlinks associated with chart items

High Low Dataset

An high low dataset is characterized by the following expressions:
  • <seriesExpression /> - currently only one series is supported inside a High-Low or Candlestick chart. However, this single series must be identified by a java.lang.Comparable value returned by this expression, and it must also be used as the series name in the chart’s legend.
  • <dateExpression /> - returns the date to which the current (high, low, open, close, volume) item refers.
  • <highExpression /> - returns a java.lang.Number value, which will be part of the data item added to the series when the dataset gets incremented.
  • <lowExpression /> - returns a java.lang.Number value, which will be part of the data item added to the series when the dataset gets incremented.
  • <openExpression /> - returns a java.lang.Number value, which will be part of the data item added to the series when the dataset gets incremented.
  • <closeExpression /> - returns a java.lang.Number value, which will be part of the data item added to the series when the dataset gets incremented.
  • <volumeExpression /> - a numeric expression that returns the volume value to use for the current data item. It is used only for Candlestick charts.
  • <itemHyperlink /> - sets hyperlinks associated with chart items

Value Dataset

This is a special chart dataset implementation that contains a single value and is used for rendering Meter and Thermometer charts. The value is collected using the <valueExpression /> expression.

Common Settings for Chart Plots

The chart plot is the area of the chart on which the axes and items are rendered. Plots differ based on the type of chart. Some plots specialize in drawing pies; others specialize in drawing bar items or lines.
Each type of plot comes with its own set of properties or attributes for customizing the chart’s appearance and behavior.
There is, however, a subset of plot properties common to all plot types. They are grouped under the <plot /> element in JRXML and can be part of any chart/plot definition in the report template. Common plot attributes are:
  • backcolor - specifies the background color for the plot.
  • orientation - specifies whether plot items will be rendered horizontally or vertically. Possible values are Horizontal and Vertical. The default is Vertical.
  • backgroundAlpha - specifies the background transparency for the plot.
  • foregroundAlpha - specifies the foreground transparency for the plot.
A plot contains also a <seriesColor /> element which customize colors for series, and their position within in the color sequence.

Specific Settings for Chart Plots

  • piePlot - it has no specific settings
  • pie3DPlot - contains the depthFactor attribute, a numeric value ranging from 0 to 1 that represents the depth of the pie as a percentage of the height of the plot area.
  • barPlot - one can show or hide tick labels, tick marks or item labels, and provides settings for both axis.
  • bar3DPlot - provides the same settings as the barPlot, and generates a 3D effect using the xOffset and yOffset attributes.
  • linePlot - one can show or hide lines connecting item points, can show or hide shapes associated with item points, and provides settings for both axis.
  • scatterPlot - like the linePlot, it can show or hide lines connecting item points, can show or hide shapes associated with item points, and provides settings for both axis.
  • areaPlot - provides settings for both axis.
  • bubblePlot - one can set the bubble dimensions by setting the scaleType attribute, and provides settings for both axis.
  • timeSeriesPlot - one can show or hide lines connecting item points, can show or hide shapes associated with item points, and provides settings for both axis.
  • highLowPlot - one can show or hide open ticks, can show or hide close ticks, and provides settings for both axis.
  • candlestickPlot - one can show or hide the volume, and provides settings for both axis.
  • meterPlot - contains specific settings for the dial shape, scale angle, measurement units, tick interval, dial color, needle color, tick color, value display font, color and format pattern, data range and meter intervals.
  • thermometerPlot - contains specific settings for the value location, mercury color, show/hide value lines, value display font, color and format pattern, data range, low range, medium range and high range.
  • multiAxisPlot - contains specific settings for axis included in the plot

Chart Types

  • pieChart - a combination of a Pie dataset and a Pie plot.
  • pie3DChart - groups a Pie dataset and a Pie 3D plot.
  • barChart - a basic combination of a Category dataset and a Bar plot.
  • bar3DChart - wraps a Category dataset and a Bar 3D plot.
  • xyBarChart - supports Time Period datasets, Time Series datasets, and XY datasets, and uses a Bar plot to render the axis and the items.
  • stackedBarChart - uses data from a Category dataset and renders its content using a Bar plot.
  • stackedBar3DChart - uses data from a Category dataset and renders its content using a Bar 3D plot.
  • lineChart - groups a Category dataset and a Line plot.
  • xyLineChart - groups an XY dataset and a Line plot.
  • areaChart - items from a Category dataset are rendered using an Area plot.
  • stackedAreaChart - items from a Category dataset are rendered using an Area plot.
  • xyAreaChart - uses data from an XY dataset and renders it through an Area plot.
  • scatterChart - wraps an XY dataset with a Scatter plot.
  • bubbleChart - combines an XYZ dataset with a Bubble plot.
  • timeSeriesChart - groups a Time Series dataset and a Time Series plot.
  • highLowChart - a combination of a High-Low dataset and a High-Low plot.
  • candlestickChart - uses data from a High-Low dataset but with a special Candlestick plot.
  • meterChart - displays a single value from a Value dataset on a dial, using rendering options from a Meter plot.
  • thermometerChart - displays the single value in a Value dataset using rendering options from a Thermometer plot.
  • multiAxisChart - contains multiple range axes, all sharing a common domain axis.
Running the Sample

Running the sample requires the Apache Ant library. Make sure that ant is already installed on your system (version 1.5 or later).
In a command prompt/terminal window set the current folder to demo/hsqldb within the JasperReports source project and run the > ant runServer command. It will start the HSQLDB server shipped with the JasperReports distribution package. Let this terminal running the HSQLDB server.
Open a new command prompt/terminal window and set the current folder to demo/samples/charts within the JasperReports source project and run the > ant test view command.
It will generate all supported document types containing the sample report in the demo/samples/charts/build/reports directory.
Then the report will open in the JasperReports internal viewer. How to make various changes to a generated chart using the JFreeChart API, which is used by JasperReports to draw the charts created with the built-in chart element. 1.1.1 Sanda Zaharia shertage@users.sourceforge.net Chart Customizers and Chart Themes

Although the JFreeChart library is a fairly complete charting package that offers great flexibility and a comprehensive range of settings to fully customize the appearance and the content of the charts it renders, the built-in chart component offered by JasperReports exposes only a subset of the library’s original charting functionality. This ensures that JasperReports charts are easily embeddable into reports and that the basic set of properties exposed through JRXML and the object model is enough for the majority of use cases.
In time, other JFreeChart settings will be exposed through the built-in chart component, but certainly JasperReports will never be able to expose all the JFreeChart settings through JRXML tags or the API.
To provide full control over chart customization even when using the built-in chart component, JasperReports can make use of either a chart theme implementation, or of a chart customizer implementation associated with the chart element, or both.
Chart themes are a more recent addition to the library and in a way they deprecate the chart customizers because they bring enhanced capabilities in controlling chart output.
A chart customizer is an implementation of the JRChartCustomizer interface that is associated with the chart element using the customizerClass attribute. The easiest way to implement this interface is by extending the JRAbstractChartCustomizer having access to parameters, fields, and variables, for more flexible chart customization based on report data.
However, it is recommended to implement and work with chart themes instead of chart customizers, because chart themes give more control over chart output, including the creation of the JFreeChart object itself. Chart customizer only allow modifying the JFreeChart object that is created externally and passed in to them. Also, chart themes affect a whole range of chart types across multiple reports and are not necessarily tied to a specific chart element within a report. They can even apply globally to all charts within a given JasperReports deployment, applying a new look and feel to all charts created within that environment.

A Simple Chart Customizer Class Example

When one implements the JRChartCustomizer interface, the only method which has to be implemented is:

public void customize(JFreeChart chart, JRChart jasperChart);

The Charts sample contains a very simple customizer class, which sets specific colors for series in a Bar chart.
First, let's take a look at the BarChartCustomizer class in the src directory:
The customize() method gets applied after the JFreeChart object is already created. Then, the only thing one have to do is to take this JFreeChart object and modify its characteristics according to some more specific needs.
In the example above, two older series colors were replaced with new ones in the bar renderer, and so, the color scheme was altered for the Bar chart.
Now, one have to tell to the JasperReports engine that a given chart should be customized using this customizer class. In the reports/BarChartReport.jrxml file this class is set as chart customizer:

<barChart>
  <chart evaluationTime="Group" evaluationGroup="ChartGroup" customizerClass="BarChartCustomizer">
   ...
  </chart>
  ...
</barChart>

Note: When running the Charts sample, one can see that the Bar chart generated reports are the only with their items colored in green and orange. All the other generated reports are sharing another color scheme.