@Override
    protected Object getActualFieldValue(String field) {
        if (inv == null) {
            throw new IllegalStateException();
        }
        return inv.getParameter(field);
    }
@ Override protected Object getActualFieldValue ( String field ) { if ( inv == null ) { throw new IllegalStateException ( ) ; } return inv . getParameter ( field ) ; }
@throws IllegalStateException 在反序列化后调用