What is the best approach to develop a reporting module for a Web based (Saas) application?

You should build them from scratch to be in control on the code so that when you need to grow or expand it will be easy for you to do it. It is cheaper to use a plug in but then you lose the scalability. I have developed all the reports for my three SaaS applications and they are working very well.

Hi,You may want to check Helical Insight. It is an open source developer friendly BI framework. Creation and consumption everything is web based. Built on backend java and frontend HTML + Javascript. It can be used to create reports, dashboards, infographs, mashups, balanced scorecards etc. It directly comes with support of D3 and C3 charts, but it also allows you to add any sort of javascripting chart which you like.For reports and dashboards creation, it allows three methods(1) Instant BI : With an integrated machine learning and NLP, it allows you to just type your question along with filters and get instant business answers. This could be in terms of reports, dashboards, geographical dashboard etc.(2) Self service BI : For slightly advanced user it provides option to drag and drop, add filters and create reports and dashboards on the fly without any technical knowledge. It has placed holders to add javascript, HTML, CSS, AJAX etc for further customization.(3) EFW : For advanced users like developers it also allows the option to use any editor and create analysis.You can check out onhttp://www.helicalinsight.com/