Spring-Data-Jpa 存储库 - 实体列名称上的下划线

Question

I am using spring-data-jpa on a spring webmvc project. I am facing an issue using query creation on a Repository of one of my Entities. Below you can see my Entity, my Repository and the Exception.

My Entity:

@Entity
@Table(schema = "mainschema")
@XmlRootElement
public class Municipalperson implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(nullable = false)
    private Integer id;

    @Basic(optional = false)
    @Column(name = "municipal_id", nullable = false)
    private Integer municipal_id;

    @Basic(optional = false)
    @Column(nullable = false, length = 60)
    private String firstname;

    public Municipalperson(Integer id, Integer municipal_id, String firstname) {
        this.id = id;
        this.municipal_id = municipal_id;
        this.firstname = firstname;
    }


    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getMunicipal_id() {
        return municipal_id;
    }

    public void setMunicipal_id(Integer municipal_id) {
        this.municipal_id = municipal_id;
    }

    public String getFirstname() {
        return firstname;
    }

    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }
}

my Repository:

@Repository
public interface MunicipalpersonRepository extends JpaRepository<Municipalperson, Integer> {

    List<Municipalperson> findByMunicipal_idOrderByLastnameDesc(int municipal_id);
}

and the exception,

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'municipalpersonRepository': Invocation of init method failed; nested exception is org.springframework.data.mapping.PropertyReferenceException: No property municipal found for type Municipalperson!  

I tried to set municipal_id as int, then as Integer and the same for the parameter municipal_id on my Repository, but none worked. Also, I renamed the Repository to findByMunicipalidOrderByLastnameDesc and findByMunicipalIdOrderByLastnameDesc but it didn't work either.

Finally I renamed the municipal_id to municipalId (underscore removed) and also renamed getters/setters and the Repository ( findByMunicipalIdOrderByLastnameDesc ) and the issue was resolved .

My question is why this is happening?

Answer 1

I solved this error by renaming field to the name without underscore.

@Column(name = "municipal_id", nullable = false)
private Integer municipalId; // <-- field was renamed

Answer 2

The underscore _ is a reserved character in Spring Data query derivation (see the reference docs for details) to potentially allow manual property path description. So there are two options you have:

1. Stick to the Java naming conventions of using camel-case for member variable names and everything will work as expected.
2. Escape the _ by using an additional underscore, ie rename your query method to findByMunicipal__idOrderByLastnameDesc(…) .

I'd recommend the former as you're not going to alienate fellow Java developers :).

Answer 3

请将以下属性添加到application.properties文件中：

spring.jpa.hibernate.naming-strategy=org.hibernate.cfg.ImprovedNamingStrategy

Answer 4

I know the question was answered a long time ago, but it can help others in the future.

According to the Docs , underscore is a special character used by spring to separate properties names. If you really want to stick with snake case notation, you can set nativeQuery to true and solve this problem:

@Query(value = "SELECT * FROM municipalperson WHERE municipal_id=?1 ORDER BY last_name DESC", nativeQuery = true)
List<Municipalperson> findByMunicipal_idOrderByLastnameDesc(int municipal_id);

Answer 5

One other approach that worked for me is to use @JsonProperty to differentiate between field name used in REST request/response and that used for database. For example:

@JsonProperty("municipalId")
private Integer municipal_id;