(Do not display relationship values) - spring-boot

Question

I have two entity with name of the article and article Category.
and they have one-to-many relationships.
I use #JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class,property = "id")
but I cant see data of article category(category_id) in spring data rest.
ArticleCategory.class
#Entity
#Table(name = "article_category")
#Getter
#Setter
public class ArticleCategory implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "category_name")
private String categoryName;
#OneToMany(cascade = CascadeType.ALL, mappedBy = "articleCategory", fetch = FetchType.LAZY)
private Set<Article> articles = new HashSet<>();
}
Article.class
#Entity
#Table(name = "article")
#Getter
#Setter
#JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class Article implements Serializable {
public Article() {
}
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "category_id", nullable = false)
private ArticleCategory articleCategory;
#Column(name = "title")
private String title;
#Column(name = "image_url")
private String image_url;
#Column(name = "short_description")
private String short_description;
#Column(name = "text")
private String text;
#Column(name = "keywords", nullable = true)
private String keywords;
#Column(name = "visit", nullable = false)
private int visit;
#Column(name = "code", nullable = false)
private UUID code;
#Column(name = "date_created")
#CreationTimestamp
private Date dateCreated;
#Column(name = "date_updated", nullable = false)
#UpdateTimestamp
private Date dateUpdated;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "user_id")
private User user;
public Article(String title, String image_url, String short_description, String text, String keywords, int visit, UUID code) {
this.title = title;
this.image_url = image_url;
this.short_description = short_description;
this.text = text;
this.keywords = keywords;
this.visit = visit;
this.code = code;
}
}
Article Repository
#CrossOrigin("http://localhost:4200")
#RepositoryRestResource(collectionResourceRel = "article", path = "article")
public interface ArticleRepository extends JpaRepository<Article,Long> {
Article findByCode(UUID uuid);
}
And this is output of spring data rest
enter image description here

Answer 1

That is exactly because you used #JsonManagedReference and #JsonBackReference. Keep in mind the following when using them:
#JsonManagedReference is the forward part of the relationship and is the one that gets serialized normally.
#JsonBackReference is the back part of the relationship and it will be omitted from serialization.
The serialized Article object does not contain a reference to the ArticleCategory object.
If you want to have any ArticleCategory data when serializing Article you can either use #JsonIdentityInfo so that one of the properties is serialized (in this case I've chosen id for both):
#Entity
#Table(name = "article")
#Getter
#Setter
#JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class Article implements Serializable{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "category_id", nullable = false)
private ArticleCategory articleCategory;
}
#Entity
#Table(name = "article_category")
#Getter
#Setter
#JsonIdentityInfo(
generator = ObjectIdGenerators.PropertyGenerator.class,
property = "id")
public class ArticleCategory implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "category_name")
private String categoryName;
#OneToMany(cascade = CascadeType.ALL,mappedBy = "articleCategory" ,fetch = FetchType.LAZY)
private Set<Article> articles=new HashSet<>();
}
If you are only interested in categoryId another possibility would be to use #JsonIgnore on private Set<Article> articles property so that it is not serialized:
#Entity
#Table(name = "article_category")
#Getter
#Setter
public class ArticleCategory implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "category_name")
private String categoryName;
#JsonIgnore
#OneToMany(cascade = CascadeType.ALL,mappedBy = "articleCategory" ,fetch = FetchType.LAZY)
private Set<Article> articles=new HashSet<>();
}
If none of those suits your needs you might need to implement your own custom serializer. You can read more about all those options at https://www.baeldung.com/jackson-bidirectional-relationships-and-infinite-recursion.

Answer 2

I solved the problem using the controller
And that's why #JsonManageRefrence and #JsonBackRefrence do not work
I replaced the lazy load with the eager load in both entity
#ManyToOne(fetch = FetchType.Eager)
#JoinColumn(name = "user_id")
#JsonManageRefrence
private User user;
#OneToMany(cascade = CascadeType.ALL, mappedBy = "articleCategory",
fetch = FetchType.Eager)
#JsonBackRefrence
private Set<Article> articles = new HashSet<>();
and then add a controller
package com.example.demo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.List;
#RestController
#RequestMapping("/getAllArticle")
public class MyController {
private ArticleRepository articleRepository;
// you must do constructor injection
#GetMapping("/getAllArticle")
public List<Article> allArticle()
{
return articleRepository.findAll();
}
}