The Definitive Guide to JasperReports - Part6

Couple of Weeks back i started reading The Definitive Guide to JasperReports By Teodor Danciu , Lucian Chirita.

Nice book written by Teodor Danciu , Lucian Chirita.

I wanted to share few qoutations i found from this book found from the next 3 chapters (11-13).

1) Subreports are an important feature of a report-generating tool. They enable you to create more complex reports and simplify the design work. Subreports are very useful when creating master-detail reports or when the structure of a single report is not sufficient to describe the complexity of the desired output document.

2) Subreport Overview

A subreport is in fact a normal report that has been incorporated into another report. You can overlap subreports or make a subreport that contains other subreports, up to any level of nesting. Subreports are compiled and filled just like normal reports. Any report template can be used as a subreport when incorporated into another report template, without anything inside it having to change.

3) A dataset is a concept that lies somewhere between a data source and a subreport. Datasets allow the engine to iterate through some virtual records, just as data sources do, but they also enable calculations and data grouping during this iteration using variables and groups. Because dataset declarations contain parameters, fields, variables, and groups, they closely resemble subreports, but they completely lack any visual content (i.e., they have no sections or layout information at the dataset level).

Datasets are useful for chart and crosstab generation when you need to iterate through data that is not the main report data source itself, in order to gather data for the chart or perform data bucketing for the crosstab. Before datasets, the use of subreports was the only way to iterate through virtual records that were nested collections of virtual records rather than part of the current report data source. However, subreports come with unwanted visual settings and tend to complicate layout and report template structure.

Main Dataset

The report data source, along with the parameters, fields, variables, and groups declared at the report level, represent the building blocks of the main dataset for the report. All report templates implicitly declare and use this main dataset.

The main dataset is responsible for iterating through the data source records, calculating variables, filtering out records, and estimating group breaks during the report-filling process.

4) JasperReports now has built-in support for charts using the new chart component, which greatly simplifies the way charts are included inside reports. Previously, users had to completely rely on scriptlets to gather the chart data and render the chart using an image element in the report template.

5) Chart Dataset Overview

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 that somewhat resembles a report variable because it gets 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, and High-Low.

The JasperReports object model uses the net.sf.jasperreports.engine.JRChartDataset interface to define chart datasets. There are implementations of this interface for each of the aforementioned dataset types.

6) 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.

7) Chart Types

JasperReports offers built-in support for several chart types. The JFreeChart library used to render the charts supports an even wider range of chart types, but the subset offered through the chart element available in JasperReports should be sufficient for the majority of reporting requirements.

About the Author

Teodor Danciu is the founder and architect of the JasperReports library, the most popular open source reporting tool, and is now working for JasperSoft. Before joining JasperSoft, Teodor worked for almost 8 years with several French IT companies as a software engineer and team leader on ERP and other medium-to-large database-related enterprise applications using mainly Java technologies and the J2EE platform. Teodor holds a B.S. in computer science from the Academy of Economic Studies in Bucharest.

Lucian Chirita joined Teodor Danciu at JasperSoft in the development of JasperReports library back in 2005, and he quickly became one of the main contributors to the project. Prior to joining JasperSoft, Lucian had 3 years of software engineering experience on several Java/J2EE products and applications. His contributions to JasperReports include support for crosstabs and integration with data query technologies such as Hibernate and OLAP. Lucian holds an M.S. in computer science from the University of Bucharest.