ation
 <code><a href="../../../../../reference/javax/security/auth/callback/Callback.html">Callback</a></code>s. A single method <code><a href="../../../../../reference/javax/security/auth/callback/CallbackHandler.html#handle(javax.security.auth.callback.Callback[])">handle(Callback[])</a></code> must be
 provided that checks the type of the incoming <code>Callback</code>s and reacts
 accordingly. <code>CallbackHandler</code>s can be installed per application. It is
 also possible to configure a system-defa