public Map act(Redirector redirector,
    SourceResolver resolver,
    Map objectModel,
    String source,
    Parameters par) throws Exception 
{
        if (this.getLogger().isDebugEnabled() == true) {
            this.getLogger().debug("BEGIN act resolver="+resolver+
                                   ", objectModel="+objectModel+
                                   ", source="+source+
                                   ", par="+par);
        }
        final String handlerName = par.getParameter("handler", null);
        if ( handlerName == null )
            throw new ProcessingException("sunRise LoginAction requires at least the handler parameter.");
        final Request request = ObjectModelHelper.getRequest( objectModel );
        // build authentication parameters
        SourceParameters authenticationParameters = new SourceParameters();
        String[] enum = par.getNames();
        if (enum != null) {
            for(int i = 0; i <  enum.length; i++) {
                final String key = enum[i];
                if ( key.startsWith("parameter_") ) {
                    String value = par.getParameter(key);
                    if ( value.startsWith("request:") ) {
                        value = request.getParameter( value.substring("request:".length()) );
                        if (value == null) value = "";
                    }
                    authenticationParameters.setParameter( key.substring("parameter_".length()),
                                                           value);
                }
            }
        }
        Map map = null;
        // authenticate
        SunRise sunRise = null;
        try {
            sunRise = (SunRise) this.manager.lookup(SunRise.ROLE);
            Object o;
            o = sunRise.authenticate( handlerName,
                                      authenticationParameters);
            if ( null == o) {
                // success
                map = sunRise.createMap();
            } else {
                request.setAttribute(Constants.REQUEST_ATTRIBUTE_FAILED_LOGIN + handlerName, o);
            }
        } finally {
            this.manager.release(sunRise);
        }
        if (this.getLogger().isDebugEnabled() == true) {
            this.getLogger().debug("END act map="+map);
        }
        return map;
}