Parent @OneToMany 映射 JPA 中的 ID 为空

Question

我在 Parent Child 关系中使用 javax.persistence.OneToMany 关系。 parent Id 为空，我已经通读了 Whosebug 中所有相关的 post，但没有得到任何线索我错过了什么。 根据提供的序列，所有相应的 PK 都在 Parent 和 Child table 中填充，但 FK 在 Child 中设置为空table

Parent Class:

@Entity
@Table(name = "DIVERSITY_TEMPLATE")
public class DiversityTemplate implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "DIVERSITY_TEMPLATE_ID", sequenceName = "DIVERSITY_TEMPLATE_ID", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "DIVERSITY_TEMPLATE_ID")
    @Column(name = "DIVERSITY_TEMPLATE_ID")
    private Integer diversityTemplateId;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "diversityTemplate", fetch = FetchType.LAZY)
    private List<DiversityTemplateAttribute> attributes = new ArrayList<>();

Child Class:

@Entity
@Table(name = "DIVERSITY_TEMPLATE_ATTRIBUTE")
@TypeName("DiversityTemplateAttribute")
public class DiversityTemplateAttribute implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "DIVERSITY_TEMPLATE_ATTR_ID", sequenceName = "DIVERSITY_TEMPLATE_ATTR_ID", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "DIVERSITY_TEMPLATE_ATTR_ID")
    @Column(name = "DIVERSITY_TEMPLATE_ATTR_ID")
    private Integer diversityTemplateAttributeId;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "DIVERSITY_TEMPLATE_ID", nullable=false, referencedColumnName = "DIVERSITY_TEMPLATE_ID")
    private DiversityTemplate diversityTemplate;

服务Class:

 diversityTemplateRepository.save(diversityTemplate);

样本json

{
  "diversityTemplateId": 0,
  "attributes": [{
    "diversityTemplateId": 0,
    "diversityTemplateAttributeId": 0,
  }, {
    "diversityTemplateId": 0,
    "diversityTemplateAttributeId": 0,
  }]
}

求推荐。

Answer 1

通常空 FK 列来自仅设置关系的一侧。

我想你有以下

DiversityTemplate diversityTemplate = ...
diversityTemplate.getAttributes().add(...)
...
diversityTemplateRepository.save(diversityTemplate);

这是错误的，因为 DiversityTemplateAttribute 不知道 parent，只有 parent 知道他的 children。

解决这个很容易，你必须在 child 中设置 parent 引用。

diversityTemplateAttribute.setDiversityTemplate(diversityTemplate);

或者您可以将此逻辑放入 DiversityTemplate 中的方法中，该方法会自动将属性添加到列表中 + 设置反向引用。

Answer 2

我知道为时已晚，但你也可以...

Parent Class:

@Entity
@Table(name = "DIVERSITY_TEMPLATE")
public class DiversityTemplate implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "DIVERSITY_TEMPLATE_ID", sequenceName = "DIVERSITY_TEMPLATE_ID", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "DIVERSITY_TEMPLATE_ID")
    @Column(name = "DIVERSITY_TEMPLATE_ID")
    private Integer diversityTemplateId;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "DIVERSITY_TEMPLATE_ID")
    private List<DiversityTemplateAttribute> attributes = new ArrayList<>();

Child Class:

@Entity
@Table(name = "DIVERSITY_TEMPLATE_ATTRIBUTE")
@TypeName("DiversityTemplateAttribute")
public class DiversityTemplateAttribute implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "DIVERSITY_TEMPLATE_ATTR_ID", sequenceName = "DIVERSITY_TEMPLATE_ATTR_ID", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "DIVERSITY_TEMPLATE_ATTR_ID")
    @Column(name = "DIVERSITY_TEMPLATE_ATTR_ID")
    private Integer diversityTemplateAttributeId;

    @ManyToOne(fetch = FetchType.LAZY)
    private DiversityTemplate diversityTemplate;

服务Class:

diversityTemplateRepository.save(diversityTemplate);

This way you DON'T NEED TO DO PARENT ENTRY IN EACH CHILD. it will do by itself. you just need to save parent that's it.

快速完成我所做的步骤。

Removed mappedBy from Parent.

Added @JoinCollumn foreign key in Parent

Removed @JoinCollumn from Child.

希望对您有所帮助。

Answer 3

@JsonManagedReference 
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "DIVERSITY_TEMPLATE_ID")
    private List<DiversityTemplateAttribute> attributes = new ArrayList<>();
.
.
.
.
@JsonBackRefrence
 @ManyToOne(fetch = FetchType.LAZY)
    private DiversityTemplate diversityTemplate;

这些 JsonManagedReference 和 JsonBackReference 由 jackson 库提供，让 JPA 知道它 class 它应该序列化以及它不应该序列化......这样我们就可以避免无限递归......更多关于这个在 here!

Parent @OneToMany 映射 JPA 中的 ID 为空

Parent Id null in @OneToMany mapping JPA

java

hibernate

jpa

persistence

one-to-many

我知道为时已晚，但你也可以...