Generic elements are built-in placeholders to be declared in a report template at report design time, in order to reserve space for special content available only at export time, generated in a specific manner by different exporters. At report filling time generic elements are processed into generic print elements that reserve room for their future content and evaluate report element expressions. Expression results will be stored as parameter values in the generic print element.
The necessity of generic elements comes from the fact that some output formats do provide dedicated support for embedding various objects that are not available in the JasperReports built-in elements gallery. Such an example is the case of embedding Flash movies in reports when they are exported to HTML format. JasperReports deals naturally with displaying text, shapes and images, but there is no built-in element for displaying Flash movies. When exporting to HTML, the empty space reserved by the generic element can be filled with specific Flash movie content generated by the HTML export handler registered for Flash movies type.