java - Spring Data JPA Query By Example 与相关实体

Question

我似乎无法添加匹配相关实体的 QueryByExample 探针。

@Entity
@Data
public class ArtistEntity implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    private String description;
    @ManyToMany(fetch = FetchType.EAGER)
    private Set<GenreEntity> genreList = new HashSet<>();
    @Version
    private Long version;
}

---

@Entity
@Data
public class GenreEntity implements Serializable {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    @Version
    private Long version;
}

---

@Repository
public interface ArtistRepository extends JpaRepository<ArtistEntity, Long> {
}

当我尝试下面的查询时，根据 Hibernate 的日志，我的探测器没有针对流派运行任何条件

GenreEntity genreEntity = new GenreEntity();
genreEntity.setName("Heavy Metal");

ArtistEntity artistEntity = new ArtistEntity();

Set<GenreEntity> genreEntitySet = new HashSet<>();
genreEntitySet.add(genreEntity);

artistEntity.setGenreList(genreEntitySet);

Example<ArtistEntity> example = Example.of(artistEntity);
Pageable pagination = PageRequest.of(0, 10);
artistRepository.findAll(example, pagination);

---

我还尝试查看有关 QBE 的 Spring Data JPA 文档，但我没有找到任何具体提及此限制的内容，这让我假设这是一种意外行为。

Answer 1

目前，您不能使用 Query By Example 执行此操作.

spring 文档声明这仅适用于 SingularAttribute。

Currently, only SingularAttribute properties can be used for property matching. https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#query-by-example.running

您想按 Set<GenreEntity> (genreList) 属性进行搜索，这是一个 PluralAttribute .无法通过该字段进行搜索。

构建查询时将忽略它，如下所示:https://github.com/spring-projects/spring-data-jpa/blob/master/src/main/java/org/springframework/data/jpa/convert/QueryByExamplePredicateBuilder.java#L127

您可以使用Specification .

Advanced Spring Data JPA - Specifications and Querydsl. https://spring.io/blog/2011/04/26/advanced-spring-data-jpa-specifications-and-querydsl/

为此，您需要从接口(interface) JpaSpecificationExecutor 进行扩展:

public interface ArtistRepository extends JpaRepository<ArtistEntity>, JpaSpecificationExecutor<ArtistEntity> {
}

• 你还需要实现你的自定义 Specification<T> .
• 然后你可以使用findAll(Specification<T> spec, Pageable pageable) .