Exporters are used to export the contents of a report. They are the output format processors used by the library implementation. Each supported output format needs a Exporter implementation in order to be available to the library.
A exporter implementations are loaded at plugin initialization and invoked at RENDER_RESPONSE phase to transform a pre-filled report instance into a human readable report. Many output formats are currently supported by the actual version of JasperReports JSF-Plugin, but you can provide your owns providing an implementation of the Exporter interface.
All of the Exporters provided by the plugin are "exporter-bridges", in other worlds, they have been implementing extending the ExporterBase class and instantiating a net.sf.jasperreports.engine.JRExporter to perform the actual rendering.
Once you have implemented your own Exporter you need to configure it as a service that can be loaded from the classpath. The way this is done is using the file META-INF/services/net.sf.jasperreports.jsf.engine.Exporter which must be also in the classpath.
The information of that file is similar than the specified at Service Provider but not exactly, there is a bit difference that must be considered. That difference consists in each line of the file must be a pair where the first part is the supported format and the last one is the Exporter implementation class name. When no export format is specified, the provided Exporter will be considered the default one. Here is a code snippet which is exactly the one provided by default in this plugin:
:net.sf.jasperreports.jsf.engine.export.PdfExporter docx:net.sf.jasperreports.jsf.engine.export.DocxExporter pdf:net.sf.jasperreports.jsf.engine.export.PdfExporter csv:net.sf.jasperreports.jsf.engine.export.CsvExporter html:net.sf.jasperreports.jsf.engine.export.HtmlExporter jexcel:net.sf.jasperreports.jsf.engine.export.JExcelApiExporter rtf:net.sf.jasperreports.jsf.engine.export.RtfExporter text:net.sf.jasperreports.jsf.engine.export.TextExporter xls:net.sf.jasperreports.jsf.engine.export.XlsExporter xml:net.sf.jasperreports.jsf.engine.export.XmlExporter
You can also replace one of the provided Exporter's by one written by yourself. However, this is not recommended so do it by your own risk.