 handler specific object containing
 the desired context. A <code>null</code> value is returned if
 the corresponding handler has been registered, and the value
 of the corresponding context is null.</dd>
<dt><span class="throwsLabel">Throws:</span></dt>
<dd><code><a href="http://docs.oracle.com/javase/8/docs/api/java/lang/IllegalArgumentException.html?is-external=true" title="class or interface in java.lang">IllegalArgumentException</a></code> - if a <code>PolicyContextHandler</code> has not been registere