A Filler is a intermediate point in the report rendering process. Its work consist on take the values established in the report and source components converted to its appropriate types (sources and reports) and generate a net.sf.jasperreports.engine.JasperPrint object which represents the final report filled with data. Such an object can be used in further requests to generate human readable output in any format supported by the plugin.
The default filler implementation is responsible of processing report parameters, subreports (and their parameters) and implicit objects. Users can extend this functionality providing Filler implementations that will be loaded following the Service Provider specification.
A user provided Filler must extends the class FillerWrapper so the user provided implementation can delegate its work to the default implementation when required.