使用@Inheritance JPA属性时插入顺序无效

Question

我已经在DB2 DB上调优了Eclipselink持久化提供程序。下面列出了3个简化定义的表格：

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;
    }
   ...
}

DerivedEntity：

@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不在插入到SECONDARY表之前插入新记录到DERIVED表？

附注:当没有使用SECONDARY表(仅限ROOT和DERIVED表)或没有使用继承(DERIVED表生成id)时，一切都正常工作。

Answer 1

对于继承，JPA假定相关表中的外键约束引用根表。

您可以更改约束以引用根表，或者，

使用DescriptorCustomizer进行设置，

descriptor.setHasMultipleTableConstraintDependecy(true);

或,

定制OneToOneMapping，使其外键引用辅助表(JPA注解总是使其引用根表)。

但是，请记录一个bug，因为JPA连接列应该允许您定义到辅助表的外键。

EclipseLink将插入延迟到辅助表的原因是允许按表对插入进行分组，从而允许批量写入并避免数据库死锁。