javax.servlet-api version 3.0.1 has annotation folder which contains different annotation classes where servlet-api version 2.5 or below (i.e version 2.4) does not contain annotation.
Annotation represents the metadata. If you use annotation, deployment descriptor i.e. web.xml is not required. For example if you use annotation like @WebServlet("/hello")
in your servlet file then you don’t need to mention servlet mapping in web.xml file.
Some of useful Annotations are:
@HandlesTypes
@HttpConstraint
@HttpMethodConstraint
@MultipartConfig
@ServletSecurity
@WebFilter
@WebInitParam
@WebListener
@WebServlet