@WebMethod(operationName = "ReadCategory")
    public ArrayList<Category> ReadCategory(@WebParam(name = "cat_id") String cat_id) {
            Category cat  = new Category();
            ArrayList<Category> cats = new ArrayList<Category>();
            ArrayList<QueryCriteria> qc = new ArrayList<QueryCriteria>();
            if(!cat_id.equals("-1")){
                qc.add(new QueryCriteria("cat_id", cat_id, Operand.EQUALS));
            }
            ArrayList<String> fields = new ArrayList<String>();
            ArrayList<QueryOrder> order = new ArrayList<QueryOrder>();
        try {
           cats = cat.Read(qc, fields, order);
        } catch (SQLException ex) {
            Logger.getLogger(JAX_WS.class.getName()).log(Level.SEVERE, null, ex);
        }
            if(cats.isEmpty()){
                return null;
            }
        return cats;
    }