@SuppressWarnings("unchecked")
    public static <T> T insertOrUpdate(Dao dao, T obj) {
	    if (obj == null)
	        return null;
	    Entity<T> en = (Entity<T>) dao.getEntity(obj.getClass());
	    if (en.getPkType() == PkType.UNKNOWN)
	        throw new IllegalArgumentException("no support , without pks");
	    boolean doInsert = false;
	    switch (en.getPkType()) {
        case ID:
            Number n = (Number) en.getIdField().getValue(obj);
            if (n == null || n.intValue() == 0)
                doInsert = true;
            break;
        case NAME:
            if (null == en.getNameField().getValue(obj))
                doInsert = false;
            break;
        case COMPOSITE:
            doInsert = true;
            for(MappingField mf :en.getCompositePKFields()) {
                Object v = mf.getValue(obj);
                if (v != null) {
                    if (v instanceof Number && ((Number)v).intValue() != 0) {
                        continue;
                    }
                    doInsert = true;
                }
            }
        case UNKNOWN:
            throw Lang.impossible();
        }
	    if (doInsert) {
	        return dao.insert(obj);
	    } else{
	        dao.update(obj);
	        return obj;
	    }
	}