Review of Jasper Reports powered by the Slant community.
Reports can be created with Jaspersoft Studio which is availabe in a Community and Professional edition.
SpecsUpdate
PlatformsWindows, Linux, Mac, Android
TechnologyJava
Ranked in these QuestionsQuestion Ranking
Pros
Pro Has many more output formats than Nextreports
Pro Easy to learn

Pro Eclipse-based report designer is fairly easy to use
Jasperstudio report designer is easy enough to grok. It is full of features for designing your reports in a wysiwyg manner.

Pro Can be run as a service (server version) that allows deep links to individual reports or embedded with your web app as a library
You may or may not want a server version with its own learning curve and API. With Jasper you have the option of server vs library. With either one you can whip up reports and make them available in PDF, XML, HTML, CSV, XLS, RTF or TXT format. It's not very difficult to do that with JasperReports. And there are many examples out there to learn from.
Cons
Con Geared towards Java programmers
Extremely slow to load
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