Servlet Async support

[gaozq]

When I use this plugin in Tomcat 7,async processing not supported.

I'm using "DeferredResult" class in my project,and exception
java.lang.IllegalStateException: Async support must be enabled on a servlet and for all filters involved in async request processing. This is done in Java code using the Servlet API or by adding "<async-supported>true</async-supported>" to servlet and filter declarations in web.xml.
occured