在春天将列表转换为JSON格式

Question

如何通过在spring MVC项目中使用条件投影来获取json数据。 我的标准查询如下。

public List<Item> getProduct() {
    Criteria crit = session.createCriteria(Item.class);
    ProjectionList projList = Projections.projectionList();
    projList.add(Projections.property("item_code"));
    projList.add(Projections.property("item_name"));
    crit.setProjection(projList);
    List<Item> results = crit.list();
}

我的控制器类跟随

@RequestMapping(method = RequestMethod.GET, produces = "application/json")
    public @ResponseBody List<Item> ProductList() {
        List<Item> productList = poService.getProduct();
         Gson gson = new GsonBuilder().serializeNulls().create();
         System.out.println("json = " + gson.toJson(productList));
        return productList;
    }

输出为

[[3,"CELLO PINPOINT"],[5,"JOHNSON BUDS 30"],[7,"SMALL WONDER FEEDING BOTTLE 125 ML"],[45,"YERA GLASS TUMBLER T70 6PC"],[1623,"PEPSI 500 ML"],[1816,"FOOD CHOPPER"],[1819,"SCREW SET"],[5653,"AMUL KOOL200ML"]]

面对问题，因为没有以json格式输出。