Java Spring boot JPA circular referencing-CodePudding

using MySQL, Java, Spring Boot and JPA

I have two objects, user and module.

A user can have many modules and a module can have many users.

A module is structured the following way:

@Entity
@Table(name = "module")
public class Module {
    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    @ManyToMany
    @JoinTable(name="module_users",
       joinColumns = @JoinColumn(name="module_id"),
       inverseJoinColumns =  @JoinColumn(name = "user_id")
    )
    private Set<User> users = new HashSet<>();

A user is structured the following way:

@Entity
@Table(name = "user")
public class User implements Serializable {
    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY) 
    public Long id;
    public String name;
    private String email;
    @JsonIgnore
    @ManyToMany(mappedBy = "users")
    public Set<Module> modules = new HashSet<>();

Having @JsonIgnore annotation does "work" when calling modules, but I also need to call a user and its modules ideally. Any suggestions to support both of these without crashing from circular referencing?

CodePudding user response：

you can use DTO in this case check here

CodePudding user response：

Use these two annotations @JsonManagedReference and @JsonBackReference

Ref: http://www.baeldung.com/jackson-bidirectional-relationships-and-infinite-recursion

@Entity
@Table(name = "module")
public class Module {
    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;
    @ManyToMany
    @JoinTable(name="module_users",
       joinColumns = @JoinColumn(name="module_id"),
       inverseJoinColumns =  @JoinColumn(name = "user_id")
    )
    @JsonBackReference
    private Set<User> users = new HashSet<>();

A user is structured the following way:

@Entity
@Table(name = "user")
public class User implements Serializable {
    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY) 
    public Long id;
    public String name;
    private String email;
    @JsonManagedReference
    @ManyToMany(mappedBy = "users")
    public Set<Module> modules = new HashSet<>();