java JPA多链接错误实体
假设我们有4个实体：电影、工作室、站点和标签。电影、工作室和站点可以有0个或多个标记（一个标记的每个标记都有0到多个）。一部电影有0或1个站点（一个站点有0到多部电影）。一部电影有0个或多个工作室（一个工作室有0到多个电影）。我通过如下介绍TagCollection和StudioCollection实现了这些关系。TagCollection具有带电影的一对一映射，以及带Tag的多对多映射（与StudioCollection相同）。我这样做是因为：
- 我希望所有标记/工作室都转到同一个表，而不管它们附加到哪个实体
- 链接表将有一个唯一的id返回到所属实体，这意味着当我查询关系时，我永远不必指定标记是用于电影、网站还是工作室：该id是唯一的，仅存在于一个实体
此计划失败，因为当我使用一些标记保存电影并检索它时，这些标记链接到工作室或任何其他实体，但其原始所有者除外。测试如下（后面是代码）。知道我做错了什么吗？我怀疑我的链接表中的ID是错误的，但我无法证明这一点，也看不出为什么会发生这种情况（这不是因为打字错误或做作不当）。完整的代码将在here发布，以防需要更多的代码，但下面是我的实现和失败测试的一部分。谢谢你的时间
@Test
public void addedMoviesWithAttributesArePersisted() {
final MovieBuilder mb = new MovieBuilder();
mb.title("Title");
// Add a site to the movie
final Site site = new Site("Site TEst");
mb.site(site);
//Add 2 studios to the movie
final Studio studio1 = new Studio("Studio 1");
final Studio studio2 = new Studio("Studio 2");
final StudioCollection studioCollection = new StudioCollection();
studioCollection.add(Sets.newSet(studio1, studio2));
mb.studioCollections(studioCollection);
// Add 2 tags to the movie
final Tag tag1 = new Tag("Tag 1");
final Tag tag2 = new Tag("Tag 2");
final TagCollection tagCollection = new TagCollection();
tagCollection.add(Sets.newSet(tag1, tag2));
mb.tagCollection(tagCollection);
final Movie movie = mb.build();
this.underTest.persist(movie);
final Set<Movie> foundMovies = this.underTest.findByTitle("Title");
assertFalse(foundMovies.isEmpty());
assertEquals(1, foundMovies.size());
assertTrue(foundMovies.contains(movie));
final Movie foundMovie = foundMovies.iterator().next();
// This fails
assertFalse(foundMovie.getTagCollection().isEmpty());
// Querying for all entities gives this results
this.underTest.getAll();
// TagCollection: id=[1] Values=[[]]
// TagCollection: id=[2] Values=[[Tag [id=1, tagName=Tag 1], Tag [id=2, tagName=Tag 2]]]
// TagCollection: id=[3] Values=[[]]
// TagCollection: id=[4] Values=[[]]
// Site: id=[1] + Name=Site TEst] + tag=[TagCollection: id=[1] Values=[[]]]
// Studio id=[1] + Name=Studio 2] + tag=[TagCollection: id=[1] Values=[[]]]
// Studio id=[2] + Name=Studio 1] + tag=[TagCollection: id=[2] Values=[[Tag [id=1, tagName=Tag 1], Tag [id=2, tagName=Tag 2]]]]
// Movie: id=[1] + Title=Title] + tag=[TagCollection: id=[1] Values=[[]]]
}
以下是我现在的情况： 标记类
@Entity
@Table(name = "TAG")
public final class Tag {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@NotNull
@NotEmpty
@Size(min = 1)
@Column(unique = true, nullable = false)
private String tagName;
// Getter & Setter and constructors
}
标签收集：
@Entity
@Table(name = "TAG_COLLECTION")
public class TagCollection {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private long id;
@ManyToMany(fetch = FetchType.EAGER, cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH })
@JoinTable(name = "tag_link", joinColumns = @JoinColumn(name = "tagCollection_id"), inverseJoinColumns = @JoinColumn(name = "tag_id"))
private final Set<Tag> tags = new HashSet<>();
// Getter & Setter and constructors
}
地点：
@Entity
@Table(name = "SITE")
public class Site implements MovieEntity {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@NotNull
@NotEmpty
@Size(min = 1)
@Column(unique = true, nullable = false)
private String name;
@OneToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH })
@JoinColumn(name = "id")
private final TagCollection tags = new TagCollection();
// Getter & Setter and constructors
}
演播室：
@Entity
@Table(name = "STUDIO")
public class Studio implements MovieEntity, Representable, Taggable {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@NotNull
@NotEmpty
@Size(min = 1)
@Column(unique = true, nullable = false)
private String name;
@OneToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH })
@JoinColumn(name = "id")
private final TagCollection tags = new TagCollection();
// Getter & Setter and constructors
}
工作室收藏：
@Entity
@Table(name = "STUDIO_COLLECTION")
public class StudioCollection {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private long id;
@ManyToMany(fetch = FetchType.EAGER, cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH })
@JoinTable(name = "studio_link", joinColumns = @JoinColumn(name = "studioCollection_id"), inverseJoinColumns = @JoinColumn(name = "studio_id"))
private final Set<Studio> studios = new HashSet<>();
// Getter & Setter and constructors
}
电影：
@Entity
@Table(name = "MOVIE")
public class Movie {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@Column(unique = false, nullable = false)
private String title;
@OneToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH })
@JoinColumn(name = "id")
private final TagCollection tagCollection = new TagCollection();
@OneToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH })
@JoinColumn(name = "id")
private final StudioCollection studioCollection = new StudioCollection();
@ManyToOne(cascade = { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH })
@JoinColumn(name = "site_id")
private Site site;
// Getter & Setter and constructors
}
# 1 楼答案
这似乎是您所描述的：
但你的实体似乎与你的概念模型不匹配。您可以对上述ER图进行如下建模：
并像这样使用它：