web/src/main/java/org/springframework/security/web/servletapi/SecurityContextHolderAwareRequestWrapper.java
@Override
	public Principal getUserPrincipal() {
		Authentication auth = getAuthentication();

		if ((auth == null) || (auth.getPrincipal() == null)) {
			return null;
		}

		return auth;
	}
@Override
	public Principal getUserPrincipal() {
		Authentication auth = getAuthentication();

		if ((auth == null) || (auth.getPrincipal() == null)) {
			return null;
		}

		return auth;
	}
Returns the <code>Authentication</code> (which is a subclass of
<code>Principal</code>), or <code>null</code> if unavailable.

@return the <code>Authentication</code>, or <code>null</code>