Hibernate

Question

我有以下 class 具有 @OneToMany 关系，但它只是 returns 两行之一：

@Entity
@javax.persistence.Table(name = "as_itm_ext")
public class ItemExtensionEntity implements java.io.Serializable {

    @OneToMany(fetch = FetchType.EAGER, cascade = { CascadeType.ALL })
    @JoinColumns({ @JoinColumn(name = "id_itm", referencedColumnName = "id_itm", insertable = false, updatable = false) })
    public Set<ItemAttributeEntity> getItemAttributeEntities() {
        return this.itemAttributeEntities;
    }

    public void setItemAttributeEntities(Set<ItemAttributeEntity> itemAttributeEntities) {
        this.itemAttributeEntities = itemAttributeEntities;
    }
}

以及要检索的class：

@Entity
@javax.persistence.Table(name = "as_itm_att")
public class ItemAttributeEntity implements java.io.Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * AttributeKey,The key of the attribute.
     */
    private ItemAttributeEntityId id;

    /**
     * AttributeValue,The value of the attribute.
     */
    private String attributeValue;

    public ItemAttributeEntity() {
    }

    public ItemAttributeEntity(ItemAttributeEntityId id, String attributeValue) {
        this.id = id;
        this.attributeValue = attributeValue;
    }

    /**
     * AttributeKey,The key of the attribute.
     */
    @EmbeddedId
    @AttributeOverrides({
            @AttributeOverride(name = "itemId", column = @Column(name = "id_itm", nullable = false, length = 32)),
            @AttributeOverride(name = "attributeKey", column = @Column(name = "att_key", nullable = false, length = 32)) })
    public ItemAttributeEntityId getId() {
        return this.id;
    }

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

    /**
     * AttributeValue,The value of the attribute.
     */
    @Column(name = "att_value", nullable = false, length = 32)
    public String getAttributeValue() {
        return this.attributeValue;
    }

    public void setAttributeValue(String attributeValue) {
        this.attributeValue = attributeValue;
    }

}

我已经尝试将 Set 更改为 List 但没有成功（在阅读了一些关于它们之间的差异之后，更改它没有任何意义）。

我不知道发生了什么，也不确定它是否总是这样。

谢谢！

更新：尝试实施equals，没有任何反应。

Answer 1

据我了解，您需要在 ItemAttributeEntity class 中添加 ItemExtensionEntity 的引用（如@ManyToOne）和在实体的 @OneToMany 注释中添加 mappedby 属性 ItemExtensionEntity

参考：Can someone please explain mappedBy in hibernate?

@Entity
@javax.persistence.Table(name = "as_itm_ext")
public class ItemExtensionEntity implements java.io.Serializable {

    @OneToMany(mappedBy="parentEntity" ,fetch = FetchType.EAGER, cascade = { CascadeType.ALL })
    //@JoinColumns({ @JoinColumn(name = "id_itm", referencedColumnName = "id_itm", insertable = false, updatable = false) })
    public Set<ItemAttributeEntity> getItemAttributeEntities() {
        return this.itemAttributeEntities;
    }

    public void setItemAttributeEntities(Set<ItemAttributeEntity> itemAttributeEntities) {
        this.itemAttributeEntities = itemAttributeEntities;
    }
}


@Entity
@javax.persistence.Table(name = "as_itm_att")
public class ItemAttributeEntity implements java.io.Serializable {

    private static final long serialVersionUID = 1L;

    /**
     * AttributeKey,The key of the attribute.
     */
    private ItemAttributeEntityId id;

    /**
     * AttributeValue,The value of the attribute.
     */
    private String attributeValue;

    @ManyToOne
    @JoinColumn(name="<columnname>", nullable=false)
    private ItemExtensionEntity parentEntity;

    //add getter and setters

    public ItemAttributeEntity() {
    }

    public ItemAttributeEntity(ItemAttributeEntityId id, String attributeValue) {
        this.id = id;
        this.attributeValue = attributeValue;
    }

    /**
     * AttributeKey,The key of the attribute.
     */
    @EmbeddedId
    @AttributeOverrides({
            @AttributeOverride(name = "itemId", column = @Column(name = "id_itm", nullable = false, length = 32)),
            @AttributeOverride(name = "attributeKey", column = @Column(name = "att_key", nullable = false, length = 32)) })
    public ItemAttributeEntityId getId() {
        return this.id;
    }

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

    /**
     * AttributeValue,The value of the attribute.
     */
    @Column(name = "att_value", nullable = false, length = 32)
    public String getAttributeValue() {
        return this.attributeValue;
    }

    public void setAttributeValue(String attributeValue) {
        this.attributeValue = attributeValue;
    }

}

Answer 2

尝试在 itemAttributeEntities.

上使用 fetch = FetchType.LAZY

Hibernate - OneToMany 只检索一行

Hibernate - OneToMany retrieving only one row

java

postgresql

one-to-many