为什么实体无法映射列表?

问题描述

我有一个mysql表"countries"，如下

i have a mysql table "countries" as follow

| id | name | name2 | code | area | currency | language | population |
----------------------------------------------------------------------
| .. | ..   |   ... |   ...|  ....|  ...     |   ...    |   ...      |

此实体"customCountry":

this entity "customCountry":

@Entity
@Table(name="countries")
public class customCountry {
    @Id
    @Column(name = "id",table ="countries")
     private Long id;

    @Column(name = "code",table ="countries")
     private Long code;

    @Column(name = "language",table ="countries")
     private String language;

   //constructors + getters/setters
}

我有这个存储库:

@Repository
public interface customCountryRepository extends JpaRepository<customCountry,Long>{


    List<customCountry> findAll();
}

和此服务类:

@Service
@ComponentScan(basePackages="repository")
public class countriesService {

    @Autowired
    customCountryRepository customcountry_repo;

    public List<customCountry> loadcustomcountries()
    {
        List<customCountry> validcustomcountries = customcountry_repo.findAll();
        System.out.println("size: "+validcustomcountries.size());
        return validcustomcountries;
    }
}

问题是，当我在控制器中调用此服务方法时，我发现size = 0，但是我不明白为什么，但是我认为我很好地管理了属性和列之间的映射.谢谢

the problem is that when i called this service method in my controller , i find out that the size = 0 , but i don't see why , i think that i well managed the mapping between attributes and columns though .thank you

推荐答案

您可以从存储库类中删除 List<customCountry> findAll(); .

You can remove List<customCountry> findAll(); from repository class.

由于您已经扩展了 JpaRepository<customCountry,Long> ，因此具有此方法.

As you had already extended JpaRepository<customCountry,Long>, it's have this method.

当您在存储库中提供该方法而不是其实现时.这引起了一个问题.

As you are providing that method in repository but not implementation of it.That is causing an issue.

只需尝试将其删除.

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