休眠@OneToMany關系

Question

我在@OneToMany關系上遇到了一些麻煩。 第一實體代表某種商品。

@Entity(name = "ARTIQULE")
public final class ArtiquleEntity extends CustomEntity{

@Id
@Column(name = "ID")
public Long id;

@NotNull
@Column(name = "METRIC_ID")
public Long metricId;

@NotNull
@Column(name = "STATUS_ID")
public Long statusId;

@NotNull
@Column(name = "NAME")
public String name;

@NotNull
@Column(name = "SHORT_NAME")
public String shortName;

@NotNull
@ManyToOne
@JoinColumn(name = "GROUP_ID")
public ArtGroupEntity artGroup;
}

其次是貨物分組

@Entity(name = "AR_GROUP")
public final class ArtGroupEntity extends CustomEntity {

@Id
@Column(name = "ID")
public Long id;

@NotNull
@Column(name = "GROUP_ID")
public Long groupId;

@NotNull
@Column(name = "STATUS_ID")
public Long statusId;

@NotNull
@Column(name = "NAME")
public String name;

@NotNull
@Column(name = "L")
public Integer left;

@NotNull
@Column(name = "R")
public Integer right;

@NotNull
@OneToMany(mappedBy = "artGroup", fetch = FetchType.EAGER)
public List<ArtiquleEntity> artiquleEntities;
}

當我做出類似“從AR_GROUP列表中選擇列表”的選擇時。 休眠為每個組創建一個選擇，為什么不使用外部聯接？ 否則是不可能的。

Hibernate: select artgroupen0_.ID as ID1_0_, artgroupen0_.GROUP_ID as GROUP_ID2_0_, artgroupen0_.L as L3_0_, artgroupen0_.NAME as NAME4_0_, artgroupen0_.R as R5_0_, artgroupen0_.STATUS_ID as STATUS_I6_0_ from AR_GROUP artgroupen0_
Hibernate: select artiquleen0_.GROUP_ID as GROUP_ID2_1_0_, artiquleen0_.ID as ID1_1_0_, artiquleen0_.ID as ID1_1_1_, artiquleen0_.GROUP_ID as GROUP_ID2_1_1_, artiquleen0_.METRIC_ID as METRIC_I3_1_1_, artiquleen0_.NAME as NAME4_1_1_, artiquleen0_.SHORT_NAME as SHORT_NA5_1_1_, artiquleen0_.STATUS_ID as STATUS_I6_1_1_ from ARTIQULE artiquleen0_ where artiquleen0_.GROUP_ID=?
Hibernate: select artiquleen0_.GROUP_ID as GROUP_ID2_1_0_, artiquleen0_.ID as ID1_1_0_, artiquleen0_.ID as ID1_1_1_, artiquleen0_.GROUP_ID as GROUP_ID2_1_1_, artiquleen0_.METRIC_ID as METRIC_I3_1_1_, artiquleen0_.NAME as NAME4_1_1_, artiquleen0_.SHORT_NAME as SHORT_NA5_1_1_, artiquleen0_.STATUS_ID as STATUS_I6_1_1_ from ARTIQULE artiquleen0_ where artiquleen0_.GROUP_ID=?
Hibernate: select artiquleen0_.GROUP_ID as GROUP_ID2_1_0_, artiquleen0_.ID as ID1_1_0_, artiquleen0_.ID as ID1_1_1_, artiquleen0_.GROUP_ID as GROUP_ID2_1_1_, artiquleen0_.METRIC_ID as METRIC_I3_1_1_, artiquleen0_.NAME as NAME4_1_1_, artiquleen0_.SHORT_NAME as SHORT_NA5_1_1_, artiquleen0_.STATUS_ID as STATUS_I6_1_1_ from ARTIQULE artiquleen0_ where artiquleen0_.GROUP_ID=?

謝謝您的回復。

Answer 1

多個正在運行的查詢可能是由於n + 1問題。

使用JOIN FETCH在一個查詢中獲取父級和所有映射的子級實體。

看看這個類似的答案。

Answer 2

通過使用hql join fetch解決了問題，在我的選項中選擇如下所示

from AR_GROUP list left outer join fetch list.artiqules