Mongodb和Springboot返回FindByaAttribute的空列表

在我实现的findByville方法上，我得到了一个空的对象列表。 这是我的控制器：

@RestController
public class CatalogController {
    @Autowired
    CatalogService catServ;
 @RequestMapping(path="/findByVille",method= RequestMethod.GET)
    public  int findByVille(@RequestParam("ville") String ville){
     ArrayList<Catalog> CatList=new ArrayList<>();
     CatList=catServ.findByVille(ville);
     if(CatList==null){
        return -1;
     }
     return CatList.size();
 }
}

编辑：*** 我的存储库：

@Repository
public interface CatalogRepository extends MongoRepository<Catalog,String> {

    ArrayList<Catalog> findByVille(String ville);
    ArrayList<Catalog> findByCategories_Nom(String nom);

@存储库
公共接口CatalogRepository扩展了MongoRepository{
ArrayList findByVille（弦乐村）；
ArrayList findByCategories_Nom（字符串名称）；

这就是我运行项目时得到的结果：

---

你能显示你的存储库吗？啊，是的，我添加了它。

{"_id":{"$oid":"5fb45837bf4f57b4a1effa30"},
"nom":"ElectroPlanet Massira","address":"18,avnmassira",
"ville":"Marrakech",
"categories":[{"nom":"Smartphones",
"produits":[{"reference":"LG-8X-PRO","libelle":"LG Gran","marque":"LG","price":1652.59,"stock":15,"image":"image/lg_phone_in_apretty_case.jpeg",
"dimension":{"longueur":12.56,"largeur":7.6,"hauteur":1},
"caracteristiques":["red","153g","Metal"],
"reviews":[{"nom":"anonymous","stars":2,"commentaire":"loreom ipsilom jdbf"}]}]},{"nom":"ElectroBeauty","produits":[{"reference":"BR-XLS-63","libelle":"Epilateur","marque":"Braun","price":350,"stock":26,"image":"image/braun_epilateur_electro.jpeg","dimension":{"longueur":0,"largeur":null,"hauteur":5.32},"carateristiques":["Batteries","Antibumps","Garanti 2 ans"],"reviews":[{"nom":"Sarah","stars":4,"commentaire":"Parfaite!"}]}]}]}

@Repository
public interface CatalogRepository extends MongoRepository<Catalog,String> {

    ArrayList<Catalog> findByVille(String ville);
    ArrayList<Catalog> findByCategories_Nom(String nom);