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JFreeReport is a successful embedded reporting engine. By providing a high degree of flexibility and minimal requirements for the execution environment, JFreeReport can be integrated into most programms programs with little effort.
The original design of the library itself was driven by the need to easily print Swing-TableModels. During the last four years, the original design of JFreeReport got transformed into a complete report generator system. It is important to note, that the original design did not include or anticipate the features implemented today.
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- Strict separation of data processing ("the reporting") and layouting ("content creation")
- Preserve the unmatched flexiblity flexibility of the report processing. JFreeReport allows to reconfigure the report definition while the report is being processed. (As far as I know, no other reporting engine allows that.) With this feature, one is able to create even irregular structures, as long as the rules for that can be implemented as Java-Function.
- Maintain JFreeReport's great extensibility at all levels of the library's architecture (OutputFormats, Functions, Report types, data sources, GUI, etc)
- create an simple, well structured codebase, which can be understood by everyone.
- Keep the system dependencies and requirements minimal, maximize the scalability.
Naturally, deep changes to the engine influence all other programmsprograms, which use JFreeReport. It is unavoidable that the changed API will be incompatible to any previously released version. As even minor API changes will break programms programs anyway, our development will follow that path with full-force, happily refactoring or removing all ugly code. Once the JFreeReport 0.9 release is feature complete, the API will be driven to stability. At that point, only show-stoppers, complex features or bug-fixes will cause non-backward-compatible changes. Once JFreeReport reaches 1.0, the API will be frozen for long-term maintainancemaintenance. At that point, JFreeReport's code will maintain backward compatibility at all costs.
Reports which use the API to create the report definition from scratch, will not be compatible with the new release. There will be no easy upgrade-path for these reports, as most classes referenced by that legacy code will be gone and the reporting logic will be changed radically. Applications, which use the XML definitions will enjoy an easier upgrade-path. A compatibility layer will be provided, which takes care of most of the gory details of transforming old report definitions into the new format. Of course, report definitions kept in the old format will not be able to use exciting new features.
The compatibilty compatibility layer consists of an XML-parser for the old report definitions and several LayoutController implementations to emulate the old behaviour of the engine. This allows to execute the old reports without explicitly porting them to the new system. For user defined functions, custom mapping rules have to be defined and/or implemented by the user.
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A strict separation of all subsystems and all the state machines involved ensures, that the reporting engine has a simple and small core.
The layouting and content generation subsystem has been fully decoupled from the JFreeReport core. The report engine generates the input events for the 'input-feed's of LibLayout. Neither does JFreeReport know the internals of Liblayout nor is LibLayout a JFreeReport specific extension. The layouting engine has been explicitly designed as an independent library. That separation reduces the tight coupeling coupling between both libraries and increases the flexibility of the entire system.
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