没有主键或连接表的Hibernate多对一关系

问题

我想首先说我意识到数据库结构很糟糕，但我现在无法改变它。

话虽这么说，我需要在Hibernate（4.2.1）中创建一对多，双向关系，它不涉及主键（只有关系的“父”侧的唯一键）而且没有连接表。 表示此关系的外键是从“子”到“父”的后向指针（见下文）。 我搜索并尝试了各种不同的注释配置而没有运气。 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 ); 

参考：

 PART_RELEASE GLOBAL_PART ------------------- ------------ PART_RELEASE_ID (PK) GLOBAL_PART_ID (PK) COLLECTION_ID -------------> RELEASES (UK) 

Java的

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 releases; public Long getGlobalPartId() { return globalPartId; } public void setGlobalPartId(Long globalPartId) { this.globalPartId = globalPartId; } public Set getReleases() { return releases; } public void setReleases(Set 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！！

Answer 1

首先，在双向关联中，始终存在用于定义映射的所有者侧，以及由mappedBy属性的存在标记的反向侧。

在OneToMany关联中，所有者方总是多方（在您的情况下为PartRelease）。

此外，默认情况下，连接列引用它引用的实体的ID。 由于它不是您想要的，您必须指定引用的列名称。

当然，必须映射RELEASES列：

 public class GlobalPart extends ModelBase implements Serializable { @OneToMany(fetch = FetchType.EAGER, mappedBy = "globalPart") private Set partReleases; @Column(name = "RELEASES") private Long releasesNumber; } public class PartRelease extends ModelBase implements Serializable { @ManyToOne @JoinColumn(name = "COLLECTION_ID", referencedColumnName = "RELEASES") private GlobalPart globalPart; } 

文档中很好地描述了关联。 你应该读它。

Answer 2

如本文所述 ，无论何时需要使用父端的非主键列映射@ManyToOne ，都必须使用@JoinColumn批注的referencedColumnName属性。

 @ManyToOne(fetch = FetchType.LAZY) @JoinColumn( name = "RELEASES", referencedColumnName = "COLLECTIONGID" ) 

我为@ManyToOne使用了@ManyToOne因为默认情况下使用了EAGER提取，这对性能非常不利 。