我有一个一对一的关系 Media
实体和 MediaAnalysis
实体所在Media
实体是一个抽象基类:
新闻报道实体
@Entity
@DiscriminatorValue("N")
public class NewsReport extends Media {
@Column(name = "BODY", nullable = false)
private String body;
NewsReport(){}
public NewsReport(String title, String link, String author, String body) {
super(title, link, author);
this.body= body;
}
public String getBody() {
return body;
}
}
媒体实体
@Entity
@Inheritance(
strategy = InheritanceType.SINGLE_TABLE
)
@DiscriminatorColumn(name = "TYPE", length = 1, discriminatorType = DiscriminatorType.STRING)
public abstract class Media {
@Id
@GeneratedValue(strategy= GenerationType.AUTO)
private Long id;
@Column(name = "TITLE", nullable = false)
private String title;
@Column(name = "LINK", length = 500, nullable = false)
private String link;
@Column(name = "AUTHOR", length = 45, nullable = false)
private String author;
@OneToOne(mappedBy = "media")
private MediaAnalysis analysis;
Media(){}
public Media(String title, String link, String author) {
this.title = title;
this.link = link;
this.author = author;
}
// getters
public Optional<MediaAnalysis> getAnalysis() {
return Optional.ofNullable(analysis);
}
}
媒体分析
@Entity
public class MediaAnalysis {
@Id
@GeneratedValue(strategy= GenerationType.AUTO)
private Long id;
@Column(name = "SUCCESS", nullable = false)
private Boolean success;
@OneToOne
@JoinColumn(
name = "MED_ID",
nullable = false,
foreignKey = @ForeignKey(name="MEA_MED_FK")
)
private Media media;
@Column(name = "CONTENT", nullable = false)
private String content;
MediaAnalysis() { }
public MediaAnalysis(Media media, Boolean success, String content) {
this.media = media;
this.success = success;
this.content = content;
}
// getters
public Media getMedia() {
return media;
}
public String getContent() {
return content;
}
}
现在当我想使用我的
AnalysisRepository.getByMedia(..a NewsReport...)
public interface AnalysisRepository extends JpaRepository<MediaAnalysis,Long> {
@Query("SELECT a FROM MediaAnalysis a LEFT JOIN FETCH a.media WHERE a.media = ?1")
Optional<MediaAnalysis> getByMedia(Media media);
}
查找
MediaAnalysis
来自 NewsReport
例如,我希望 hibernate 运行单个 SELECT
查询,例如:SELECT m.* from mediaanalysis m where m.med_id = ?
但是,当我启用查询日志记录时,我看到 2:
DEBUG o.h.SQL:92 - select mediaanaly0_.id as id1_0_0_, media1_.id as id2_1_1_, mediaanaly0_.med_id as med_id3_0_0_, mediaanaly0_.success as success2_0_0_, media1_.author as author3_1_1_, media1_.link as link4_1_1_, media1_.title as title5_1_1_, media1_.body as body6_1_1_, media1_.type as type1_1_1_ from mea_media_analysis mediaanaly0_ left outer join med_media media1_ on mediaanaly0_.med_id=media1_.id where mediaanaly0_.med_id=?
TRACE o.h.t.d.s.BasicBinder:65 - binding parameter [1] as [BIGINT] - [1]
DEBUG o.h.SQL:92 - select mediaanaly0_.id as id1_0_1_, mediaanaly0_.med_id as med_id3_0_1_, mediaanaly0_.success as success2_0_1_, media1_.id as id2_1_0_, media1_.author as author3_1_0_, media1_.link as link4_1_0_, media1_.title as title5_1_0_, media1_.body as body6_1_0_, media1_.type as type1_1_0_ from mea_media_analysis mediaanaly0_ inner join med_media media1_ on mediaanaly0_.med_id=media1_.id where mediaanaly0_.med_id=?
TRACE o.h.t.d.s.BasicBinder:65 - binding parameter [1] as [BIGINT] - [1]
看来要先选
MediaAnalysis
正如预期的那样,但是还有一个似乎没有必要的其他查询。我能分辨出这两个查询之间的唯一区别是连接类型。我认为问题与 Media
有关遗产。为什么会这样? + 我该怎么做才能确保这是一个查询?
进一步说明,如果我删除
@Query
从我的存储库中实际上有 三 查询!。DEBUG o.h.SQL:92 - select mediaanaly0_.id as id1_0_, mediaanaly0_.med_id as med_id3_0_, mediaanaly0_.success as success2_0_ from mea_media_analysis mediaanaly0_ left outer join med_media media1_ on mediaanaly0_.med_id=media1_.id where media1_.id=?
TRACE o.h.t.d.s.BasicBinder:65 - binding parameter [1] as [BIGINT] - [1]
DEBUG o.h.SQL:92 - select media0_.id as id2_1_0_, media0_.author as author3_1_0_, media0_.link as link4_1_0_, media0_.title as title5_1_0_, media0_.body as body6_1_0_, media0_.type as type1_1_0_, mediaanaly1_.id as id1_0_1_, mediaanaly1_.med_id as med_id3_0_1_, mediaanaly1_.success as success2_0_1_ from med_media media0_ left outer join mea_media_analysis mediaanaly1_ on media0_.id=mediaanaly1_.med_id where media0_.id=?
TRACE o.h.t.d.s.BasicBinder:65 - binding parameter [1] as [BIGINT] - [1]
DEBUG o.h.SQL:92 - select mediaanaly0_.id as id1_0_1_, mediaanaly0_.med_id as med_id3_0_1_, mediaanaly0_.success as success2_0_1_, media1_.id as id2_1_0_, media1_.author as author3_1_0_, media1_.link as link4_1_0_, media1_.title as title5_1_0_, media1_.body as body6_1_0_, media1_.type as type1_1_0_ from mea_media_analysis mediaanaly0_ inner join med_media media1_ on mediaanaly0_.med_id=media1_.id where mediaanaly0_.med_id=?
TRACE o.h.t.d.s.BasicBinder:65 - binding parameter [1] as [BIGINT] - [1]
最佳答案
我没有使用 JpaRepository 的经验,只是(很多)使用 Hibernate(主要是 CriteriaBuilder),但有一些想法:
@OneToOne
仅在两个实体之一中(根据您的示例应该是 MediaAnalysis)MediaAnalysis
作为 1:n 关系(好像每个媒体可能有多个 MediaAnalysis
,这很可能在我的理解中,只是可能不在您的域中)。 看看是否有任何对生成的查询有帮助。
关于spring - JPA 一对一映射与继承 : 2 Queries for what should be one,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/48169664/