Question

问题

我首先要说的是，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）中创建一对多的双向关系，它不涉及主键（只有关系的“父”侧的唯一键））并没有连接表。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。是我要求的可能吗？

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)

爪哇

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;
    }

}

非常感谢任何帮助!!

Answer 1

首先，在双向关联中，始终存在一个定义映射的所有者方，以及一个由mappedBy属性的存在标记的反面。

在OneToMany协会中，所有者方总是多方（在你的情况下是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。

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;

}

the documentation中详细描述了关联。你应该阅读它。

Answer 2

正如this article中所述，每当您需要使用父级的非主键列映射@ManyToOne时，您必须使用referencedColumnName属性{ {1}}注释。

@JoinColumn

我将@ManyToOne(fetch = FetchType.LAZY) @JoinColumn( name = "RELEASES", referencedColumnName = "COLLECTIONGID" )用于FetchType.LAZY，因为默认使用的是EAGER提取，very bad for performance。

没有主键或连接表的Hibernate多对一关系

问题

数据库

爪哇

2 个答案: