Dynamic Graphs(Ajax) in JSP

I have a requirement to display bar graphs, pie charts(3D) and histograms in a JSP page.
I am looking for Java APIs or Javascript based frameworks to generate graphs. The graph will have to be dynamically regenerated (Ajax) on the basis of user selection.
Eg: User has multiple accounts at a water company and a graph representing the consumption of a particular account has to be displayed. If the user selects a different account from the drop down, the graph should dynamically change(without reloading the complete page) and represent the consumption of currently selected account.

After going through the forums, I have realized that Cewolf as a popular Java API to display graphs. There are other frameworks like YUI which can also be used.
Can you please suggest what would be the best option for this requirement.

Thanks,
Amandeep

I've done recently graphics in JSP using ExtJS, but i'm using now JFree Chart and Ireport Graphics for generat them, i think that you should see this site :

Sencha Ext JS 4 Preview — Drawing & Charts

For Dinamic graphics, i used FusionCharts, a time ago:

FusionCharts v3

I hope I have helped