rincipal for a 
  remote method invocation on the service endpoint instance.</div>
<dl>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>A <code>java.security.Principal</code> for the 
           authenticated principal associated with the current
           invocation on the servlet endpoint instance;
           Returns <code>null</code> if there no authenticated
           user associated with a method invocation.</dd>
<dt><span class="seeLabel">See Also:</span></dt>
<dd><a href="https://docs.oracle