Servlet 3.1 was in Public Review in Janurary 2013. And it is in Proposed Final Draft now. Most of the new features are related to security.
In this following, I will highlight features since Servlet 3.1 Public Review:
add new API javax.servlet.http.Part#getSubmittedFileName
add new API javax.servlet.ServletContext#getVirtualServerNameThis API allows a JASPIC module to be registered in a Servlet...