2

我在 DB2 DB 上调整了 Eclipselink 持久性提供程序。下面列出了简化定义的 3 个表格：

CREATE TABLE root
(
    id       CHAR(32) NOT NULL PRIMARY KEY,
    rec_type VARCHAR(20)
);

CREATE TABLE derived
(
    id CHAR(32) NOT NULL PRIMARY KEY,
    ...
);
ALTER TABLE derived ADD CONSTRAINT fk_derived_to_root FOREIGN KEY (id) REFERENCES root(id);

CREATE TABLE secondary
(
    derived_id NOT NULL PRIMARY KEY,
    ...
);
ALTER TABLE secondary ADD CONSTRAINT fk_secondary_to_derived FOREIGN KEY (derived_id) REFERENCES derived(id);

下面列出了这些实体的 Java 实体类，RootEntity：

@javax.persistence.Table(name = "ROOT")
@Entity
@DiscriminatorColumn(name = "REC_TYPE")
@Inheritance(strategy = InheritanceType.JOINED)
public class RootEntity {
    private String id;

    @javax.persistence.Column(name = "ID")
    @Id
    @GeneratedValue(generator = "system-uuid")
    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    private String principalType;
    @Column(name = "PRINCIPAL_TYPE")
    public String getPrincipalType() {
        return principalType;
    }

    public void setPrincipalType(String principalType) {
        this.principalType = principalType;
    }
   ...
}

派生实体：

@javax.persistence.Table(name = "DERIVED")
@Entity
@DescriminatorValue("DERIVED")
public class DerivedEntity extends RootEntity {
    private SecondaryEntity secondaryEntity;

    @OneToOne(mappedBy = "derived_id")
    public SecondaryEntity getSecondaryEntity() {
        return secondaryEntity;
    }

    public void setSecondaryEntity(SecondaryEntity secondaryEntity) {
        this.secondaryEntity = secondaryEntity;
    }
 ...
}

我在测试日志中没有看到派生表插入：

--INSERT INTO ROOT (ID, REC_TYPE) VALUES (?, ?)
    bind => [241153d01c204ed79109ce658c066f4c, Derived]
--INSERT INTO SECONDARY (DERIVED_ID, ...) VALUES (?, ...)
    bind => [241153d01c204ed79109ce658c066f4c, ...]
Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.3.2.v20111125-r10461): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.ibm.db2.jcc.am.fo: DB2 SQL Error: SQLCODE=-530, SQLSTATE=23503, SQLERRMC=SCHEM.SECONDARY.FK_SECONDARY_TO_DERIVED, DRIVER=3.57.82

所以问题是：为什么 Eclipselink 在插入DERIVED表之前不向表中插入新记录SECONDARY？

SECONDARYPS 当没有表（ROOT仅DERIVED表）或不使用继承（DERIVED表生成 id）时，一切正常。

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1 回答 1

2

对于继承，JPA 假定相关表中的外键约束是指根表。

您可以更改约束以引用根表，或者，

使用 DescriptorCustomizer 设置，

descriptor.setHasMultipleTableConstraintDependecy(true);

或者，

定制器 OneToOneMapping 使其外键引用辅助表（JPA 注释始终使其引用根表）。

请记录一个错误，因为 JPA 连接列应该允许您定义辅助表的外键。

EclipseLink 确实推迟插入到辅助表的原因是允许插入按表分组以允许批量写入并避免数据库死锁。

于 2012-06-26T12:36:14.423 回答