iReport Ultimate Guide

iReport Ultimate Guide
During compilation of the JRXML file (using some JasperReports classes), the XML is parsed and loaded in a JasperDesign
object, which is a rich data structure that allows you to represent the exact XML contents in memory. Without going into
details, regardless of which language is used for expressions inside the JRXML, JasperReports creates a special Java class that
represents the whole report. The report is then compiled, instanced and serialized in a JASPER file, ready for loading at any
time.
JasperReports’s speedy operation is due to all of a report’s formulas being compiled into Java-native bytecode and the report
structure being verified during compilation instead of run time. The JASPER file does not contain extraneous resources, such
as images used in the report, resource bundles to run the report in different languages, or extra scriptlets and external style
definitions. All these resources must be provided by the host application and located at run time .
3.3 Data Sources and Print Formats
Without a means of supplying content from a dynamic data source, even the most sophisticated and appealing report would be
useless. JasperReports allows you to specify fill data for the output report in two ways: parameters and data sources. Either
kinds of data are presented by means of a generic interface named JRDataSource, as shown in Figure 3-1.
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Code Example 3-1 A simple JRMXL file example, continued