As previous user has answer, spring security support the getUserPrincipal and isUserInRole. Here is how spring security does it.
When you configure spring, it can load the following filters:
http://static.springframework.org/spring-security/site/reference/html/ns-config.html#filter-stack
As part of the standard filter configuration the SecurityContextHolderAwareRequestFilter filter is loaded.
Examining the filter @ https://fisheye.springsource.org/browse/spring-security/tags/spring-security-parent-2.0.4/core/src/main/java/org/springframework/security/wrapper/SecurityContextHolderAwareRequestFilter.java?r=2514
You can see it wraps and changes the HttpServletRequest object to the SecurityContextHolderAwareRequestWrapper class which extends HttpServletRequestWrapper which implements HttpServletRequest and feed it back to the standard Servlet Filter doFilter chain. Since spring security filter should be configured as the first filter, all subsequent classes will see the SecurityContextHolderAwareRequestWrapper instead. This includes JSP pages or Servlets behind this filter.
When you make a call to isUserInRole or getUserPrincipal from the JSP page, Servlet or any framework behind this filter, it is calling the HttpServletRequest implementation from Spring Security.