JPA未获取数据引发stackoverflow错误

Question

I have a very large json to store and I divided that into following five entities and trying to store to h2 database using spring-data-jpa,inserting is working fine into database, but while fetching A object with A primary key Id, I am getting stackoverflow error, because there is circular dependency.

could someone help me to figure out what is the issue.

Top class

@Entity
@Table(name = "a")
@Data
public class A{

@Id
@Column(name = "a_id")
private String id;

@Column
private String name;

@Column
private String name2;

@Column
private String name3;

@Column
private String name4;

@Column
private String name5;

@OneToMany(cascade = CascadeType.ALL,mappedBy = "a",fetch = 
FetchType.EAGER)
@JsonManagedReference
private List<B> b;
}

Second class

@Entity
@Table(name = "b")
@Data
public class B{

@Id
@Column(name = "bname")
private String bname;

@Column
private String bVersion;

@OneToMany(cascade = CascadeType.ALL,mappedBy = "b")
@JsonManagedReference
private List<C> cs;


@ManyToOne
@JoinColumn(name = "a_id")
@JsonBackReference
private A a;
}

Third class

@Entity
@Data
public class C{

@Id
@Column(name = "cname")
private String cName;


@Column
private String cVersion;

@OneToMany(cascade = CascadeType.ALL,mappedBy = "c")
@JsonManagedReference
private List<D> ds;

@ManyToOne
@JoinColumn(name = "bname")
@JsonBackReference
private B b;
}

Fourth class

@Entity
@Data
public class D{

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name="d_id")
private long id;

@Column
private String dName;

@Column
private String dName2;


@ElementCollection
@Column
private List<String> dNames;


@OneToMany(cascade = CascadeType.ALL,mappedBy = "d")
@JsonManagedReference
private List<E> e;

@ManyToOne
@JoinColumn(name = "cname")
@JsonBackReference
private C c;

}

Fifth class

@Entity
@Data
public class E{

@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "e_id")
private long id;

@Column
private String ename;

@Column
private String eName2;


@ManyToOne
@JoinColumn(name = "e_id")
@JsonBackReference
private E e;
}

Answer 1

I also faced the same problem and spent the whole day. Finally, I found its problem with the toString method generated by Lombok using @Data annotation.

Solution:

Override, toString method and write your own implementation. If you do not want to use toString then use @Getter and @Setter instead of @Data .

Why

Note: This occurs with bi-directional relationship. Lets say I have two entity and having bi-directional relationship.

@data
Entity1{
  @oneToMany
  public List<Entity2> entity2s;

  //Added by lombok while using @Data
  @Generated
    public String toString() {
        return "entity2s=" + this.getEntity2s() + ")";
    }
}

@data
Entity2{
  @ManytoOne
  public Entity1 entity1;


  //Added by lombok while using @Data
  @Generated
  public String toString() {
    return "entity1=" + this.getEntity1() + ")";
  }

}

In above example, toString()(called by JPA) of Entity1 calles toString() of Entity2 and toString() of Entity2 calls toString() of Entity1. And that is how circular reference is building.

Note: The same goes to hashCode method.

Here is a some reference links,

https://github.com/rzwitserloot/lombok/issues/1007

https://interviewbubble.com/stackoverflow-tostring-method-when-using-lombok/