[login to view URL] is a well known Java library for pivot table that is used in Website and Analytics web applications.
[login to view URL] like is here [login to view URL]
[login to view URL] does not support multi-aggregation out of the box and it also does not support sub-total out of the box. Since this is open source the community of [login to view URL] is huge.
There are developers who has developed multi-aggregate feature separately as a plugin and sub-total feature separately as a plugin. Below are links for it
Multi-aggregate plugin : [login to view URL]
Sub-total plugin : [login to view URL]
Objective of Project : Integrate Sub-total plugin inside Multi-aggregate plugin. The Multi-aggregate plugin should be the base of the project
Note : This should not be other way round like integrating Multi-aggregate plugin inside Sub-total plugin