i want to know why my controller give nested response

Question

In Spirngboot, I have use JpaRepository when i get any of the record from one table its associated with another table record, in this case i got recursive data. example i have two tables(jobs and company), jobs have company field at entity, company have jobs field Set at company entity.

this is sample of my response

Here my Jobs entity

@Entity
public class Jobs {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @Column(unique = true)
    private String title;
    
    @ManyToOne( fetch = FetchType.LAZY)
    @JoinColumn(name = "company")
    private Company company;
..,

Company entity

@Entity
public class Company {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    
    @Column(nullable = false, unique = true)
    private String name;
    
    @Column(length = 1500)
    private String about; 

    @Column( length = 600)
    private String companyLogoLink;
    
    @OneToMany(mappedBy = "company", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private Set<Jobs> jobs;
..,

I have already tried out Lazy loader at annotation

I expect when i save any new jobs record. its return job and associated company record not jobs record which is associated with company. like

job{
   id:
   title:
   company: { 
       id:
       company_name:
       jobs: {
              avoid here repeated;
             }

Answer 1

When you fetch lazily, data is retrieved from the db on demand, when the getter is invoked.

Jackson uses getters/setters by default for serialization/deserialization. When it invokes the getter, jpa retrieves the data, then it invokes the getter on the new data when serializing it, jpa retrieves more data, and so on. I am surprised you are not getting stackoverflow error here, json format cannot represent the circular references between objects, which are absolutely legal in java.

Solutions:

1. Use the good practices - for de/serialization use DTOs (data transfer objects), not entities (which is the bad practice).
2. @JsonIgnore on the properties you don't need.
3. @JsonIdentityInfo and other jackson annotations, which can deal with circular references.