在Spring JPA中调用saveAll后，相关实体为空

Question

我有这些实体

标准化ChannelStock。Java语言

@Entity
@Table(name = "stocks")
public class NormalizedChannelStock {

    @EmbeddedId
    private NormalizedChannelStockId id;

    @Column(name = "qty")
    private int qty;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "channel_id", insertable = false, updatable = false)
    private Channel channel;

    @Column(name = "created_at", updatable = false)
    private Timestamp createdAt;

    @Column(name = "updated_at", updatable = false)
    private Timestamp updatedAt;

    public NormalizedChannelStockId getId() {
        return id;
    }

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

    public int getQty() {
        return qty;
    }

    public void setQty(int qty) {
        this.qty = qty;
    }

    public Channel getChannel() {
        return channel;
    }

    public void setChannel(Channel channel) {
        this.channel = channel;
    }

    public Timestamp getCreatedAt() {
        return createdAt;
    }

    public Timestamp getUpdatedAt() {
        return updatedAt;
    }
}

NormalizedChannelStockId。Java语言

@Embeddable
public class NormalizedChannelStockId implements Serializable {

    @Column(name = "channel_id")
    private Integer channelId;

    @Column(name = "sku")
    private String sku;

    public NormalizedChannelStockId() {
    }

    public NormalizedChannelStockId(Integer channelId, String sku) {
        this.channelId = channelId;
        this.sku = sku;
    }

    public Integer getChannelId() {
        return channelId;
    }

    public void setChannelId(Integer channelId) {
        this.channelId = channelId;
    }

    public String getSku() {
        return sku;
    }

    public void setSku(String sku) {
        this.sku = sku;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        NormalizedChannelStockId that = (NormalizedChannelStockId) o;
        return channelId.equals(that.channelId) &&
                sku.equals(that.sku);
    }

    @Override
    public int hashCode() {
        return Objects.hash(channelId, sku);
    }
}

Channel.java

@Entity
@Table(name = "channels")
public class Channel {

    @Id
    @Column(name = "channel_id")
    private int channelId;

    @Column(name = "channel_name")
    private String channelName;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "store_id", insertable = false, updatable = false)
    private Store store;

    public int getChannelId() {
        return channelId;
    }

    public void setChannelId(int channelId) {
        this.channelId = channelId;
    }

    public String getChannelName() {
        return channelName;
    }

    public void setChannelName(String channelName) {
        this.channelName = channelName;
    }

    public Store getStore() {
        return store;
    }

    public void setStore(Store store) {
        this.store = store;
    }
}

我面临的问题是

List<NormalizedChannelStock> entitiesToSave = ...
List<NormalizedChannelStock> savedEntities = normalizedChannelStockService.saveAll(entitiesToSave);

如图所示，savedentialities中返回的实体将其通道内部对象设置为null，以及其created\u at和updated\u at

这是正常的行为吗？当我在存储库上运行findAllById时，实体中的Channel被正确地延迟加载，因此我相信实体在代码中被正确映射。问题是在我保存它们之后。JPA保存后没有重新加载实体吗？

Answer 1

正如您在注释中所述，在保存之前没有设置这些值。

JPA不会为您加载它们。JPA在保存时几乎不加载任何内容，除非id是由数据库生成的。

同一问题/限制/误解的一种更常见的情况是双向关系：JPA几乎忽略了非所有权方，开发人员必须确保双方始终保持同步。

您必须自己刷新实体。请注意，仅在同一事务中加载它不会有任何效果，因为它将来自一级缓存，并且将是完全相同的实例。