I have two entities with One-to-one association between them. chatId from MetaDataEntity is the value of column id from ChatEntity.

But there is a problem when I try to create ChatEntity. In this case I get an exception that chatId for MetaDataEntity canon be nullable. How can I solve it? Is it possible to save these two entities during one request like chatRepository.save(chatEntity) to database?

@Entity
@Table(name = "chat")
data class ChatEntity(
    val name: String?,

    @OneToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "id", referencedColumnName = "chatId")
    val metaData: MetaDataEntity? = null
) {
    @Id
    @GeneratedValue
    var id: UUID? = null
}

@Entity
@Table(name = "meta_data")
data class MetaDataEntity(
    @Id
    val chatId: UUID,

    val lastBumpingActivityAt: Instant?,
)

CREATE TABLE _chat_meta_data
(
    chat_id                     uuid NOT NULL CONSTRAINT _chat_meta_data_pkey PRIMARY KEY,
    last_bumping_activity_at    timestamp
);

I have two entities with One-to-one association between them. chatId from MetaDataEntity is the value of column id from ChatEntity.

But there is a problem when I try to create ChatEntity. In this case I get an exception that chatId for MetaDataEntity canon be nullable. How can I solve it? Is it possible to save these two entities during one request like chatRepository.save(chatEntity) to database?

@Entity
@Table(name = "chat")
data class ChatEntity(
    val name: String?,

    @OneToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "id", referencedColumnName = "chatId")
    val metaData: MetaDataEntity? = null
) {
    @Id
    @GeneratedValue
    var id: UUID? = null
}

@Entity
@Table(name = "meta_data")
data class MetaDataEntity(
    @Id
    val chatId: UUID,

    val lastBumpingActivityAt: Instant?,
)

CREATE TABLE _chat_meta_data
(
    chat_id                     uuid NOT NULL CONSTRAINT _chat_meta_data_pkey PRIMARY KEY,
    last_bumping_activity_at    timestamp
);

• kotlin
• spring-data-jpa
• one-to-one

1 Answer 1

Use a shared primary key. In your MetaDataEntity, annotate the ChatEntity relationship with @MapsId so that it reuses ChatEntity’s generated ID. With cascading enabled, saving ChatEntity will persist both entities in one request.

Example:

@Entity
data class ChatEntity(
    val name: String?,
    @OneToOne(mappedBy = "chat", cascade = [CascadeType.ALL], orphanRemoval = true)
    var metaData: MetaDataEntity? = null
) {
    @Id @GeneratedValue
    var id: UUID? = null
}

@Entity
data class MetaDataEntity(
    @Id
    var chatId: UUID? = null,
    @OneToOne
    @MapsId
    @JoinColumn(name = "chat_id")
    var chat: ChatEntity,
    val lastBumpingActivityAt: Instant?
)

Now, saving ChatEntity (with metaData set) will automatically persist MetaDataEntity with the correct ID.