Java Portlet spefication168 (v1.0) has very basic portlet porgramming model and had lot of limitations for portlet development. Java Portlet spefication286 (v2.0) was developed to overcome the shortcomings on v1.0 specs(JSR 168) such as:
1. Inter portlet communicaiton (IPC) - IPC through events and public render parameters
2. Support for WSRP 2.0
3. Public render paremeters - Allows portlets to share parameters with other portlets.
4. Portlet filters and listeners.
5. Resource serving - Provide ability for portlets to server a resource
6. AJAX support