code: @Override
      public final void initialize(final Subject _subject,
                                   final CallbackHandler _callbackHandler,
                                   final Map < String, ? > _sharedState,
                                   final Map < String, ? > _options)
      {
          XMLUserLoginModule.LOG.debug("Init");
          this.subject = _subject;
          this.callbackHandler = _callbackHandler;
          readPersons((String) _options.get("xmlFileName"));
      }
docs: Initialize this LoginModule.
  
  <p> This method is called by the <code>LoginContext</code>
  after this <code>LoginModule</code> has been instantiated.
  The purpose of this method is to initialize this
  <code>LoginModule</code> with the relevant information.
  If this <code>LoginModule</code> does not understand
  any of the data stored in <code>sharedState</code> or
  <code>options</code> parameters, they can be ignored.
  
  <p>
  
  @param _subject      the <code>Subject</code> to be authenticated. <p>
  @param _callbackHandler a <code>CallbackHandler</code> for communicating
  with the end user (prompting for usernames and
  passwords, for example). <p>
  @param _sharedState state shared with other configured LoginModules. <p>
  @param _options options specified in the login
  <code>Configuration</code> for this particular
  <code>LoginModule</code>.