问题
首先我想说的是,我意识到数据库结构很糟糕,但我现在无法更改它。
也就是说,我需要在 Hibernate (4.2.1) 中创建一个一对多的双向关系,它不涉及主键(关系的“父”端只有一个唯一键) 并且没有连接表。表示这种关系的外键是从“ child ”到“ parent ”的反向指针(见下文)。我搜索并尝试了各种不同的注释配置,但没有成功。我要求的是可能的吗?
数据库
GLOBAL_PART
CREATE TABLE "GLOBAL_PART" (
"GLOBAL_PART_ID" NUMBER NOT NULL,
"RELEASES" NUMBER,
CONSTRAINT "GLOBAL_PART_PK" PRIMARY KEY ("GLOBAL_PART_ID"),
CONSTRAINT "GLOBAL_PART_RELEASES_UK" UNIQUE ("RELEASES")
);
PART_RELEASE
CREATE TABLE "PART_RELEASE" (
"PART_RELEASE_ID" NUMBER NOT NULL,
"COLLECTION_ID" NUMBER,
CONSTRAINT "PART_RELEASE_PK" PRIMARY KEY ("PART_RELEASE_ID"),
CONSTRAINT "GLOBAL_PART_RELEASE_FK" FOREIGN KEY ("COLLECTION_ID")
REFERENCES "GLOBAL_PART" ("RELEASES") ON DELETE CASCADE ENABLE
);
引用:
PART_RELEASE GLOBAL_PART
------------------- ------------
PART_RELEASE_ID (PK) GLOBAL_PART_ID (PK)
COLLECTION_ID -------------> RELEASES (UK)
Java
GlobalPart.java
@Entity
@Table(name = "GLOBAL_PART")
@SequenceGenerator(name = "SEQUENCE_GENERATOR", sequenceName = "GLOBAL_PART_SEQ")
public class GlobalPart extends ModelBase implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Column(name = "GLOBAL_PART_ID", unique = true, nullable = false)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQUENCE_GENERATOR")
private Long globalPartId;
@OneToMany(fetch = FetchType.EAGER)
@JoinColumn(name = "COLLECTIONGID")
private Set<PartRelease> releases;
public Long getGlobalPartId() {
return globalPartId;
}
public void setGlobalPartId(Long globalPartId) {
this.globalPartId = globalPartId;
}
public Set<PartRelease> getReleases() {
return releases;
}
public void setReleases(Set<PartRelease> releases) {
this.releases = releases;
}
}
PartRelease.java
@Entity
@Table(name = "PART_RELEASE")
@SequenceGenerator(name = "SEQUENCE_GENERATOR", sequenceName = "PART_RELEASE_SEQ")
public class PartRelease extends ModelBase implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Column(name = "PART_RELEASE_ID", unique = true, nullable = false)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQUENCE_GENERATOR")
private String partReleaseId;
@ManyToOne
@JoinColumn(name = "RELEASES")
private GlobalPart globalPart;
public String getPartReleaseId() {
return partReleaseId;
}
public void setPartReleaseId(String partReleaseId) {
this.partReleaseId = partReleaseId;
}
public GlobalPart getGlobalPart() {
return globalPart;
}
public void setGlobalPart(GlobalPart globalPart) {
this.globalPart = globalPart;
}
}
任何帮助将不胜感激!!
最佳答案
首先,在双向关联中,总是有一个定义映射的所有者端,以及一个由 mappedBy
属性标记的反向端。
在 OneToMany 关联中,所有者方始终是多方(在您的情况下为 PartRelease)。
此外,默认情况下,连接列会引用它引用的实体的 ID。由于这不是您想要的,因此您必须指定引用的列名。
当然,必须映射 RELEASES 列:
public class GlobalPart extends ModelBase implements Serializable {
@OneToMany(fetch = FetchType.EAGER, mappedBy = "globalPart")
private Set<PartRelease> partReleases;
@Column(name = "RELEASES")
private Long releasesNumber;
}
public class PartRelease extends ModelBase implements Serializable {
@ManyToOne
@JoinColumn(name = "COLLECTION_ID", referencedColumnName = "RELEASES")
private GlobalPart globalPart;
}
关联在 the documentation 中有详细描述.你应该读一读。
关于java - 没有主键或连接表的 Hibernate 多对一关系,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16989733/