protected static AuthProvider instantiateProvider( String propertyName )
    {
        final String className = JiveGlobals.getProperty( propertyName );
        if ( className == null )
        {
            throw new IllegalStateException( "A class name must be specified via openfire.xml or the system properties." );
        }

        try
        {
            final Class c = ClassUtils.forName( className );
            return (AuthProvider) c.newInstance();
        }
        catch ( Exception e )
        {
            throw new IllegalStateException( "Unable to create new instance of AuthProvider: " + className, e );
        }
    }
Serves the regular, non-administrative users.
xmppserver/src/main/java/org/jivesoftware/openfire/auth/AuthorizationBasedAuthProviderMapper.java