Prevent recursive association in ManyToOne hibernate

Question

It was a while since a worked with ORM on Java and currently looking for an option prevent recursive references in OneToMany-like relationships. Here is trivial sample.

@Entity
public class InnerEntity extends BaseEntity {

    private String name;

    @ManyToOne(fetch = FetchType.LAZY)
    private OuterEntity host;

    public InnerEntity() {
    }

    public InnerEntity(String name, OuterEntity host) {
        this.name = name;
        this.host = host;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public OuterEntity getHost() {
        return host;
    }

    public void setHost(OuterEntity host) {
        this.host = host;
    }

}

@Entity
public class OuterEntity extends BaseEntity {

    private String name;

    @OneToMany(mappedBy = "host")
    private List<InnerEntity> dataset;

    public OuterEntity() {
    }

    public OuterEntity(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public List<InnerEntity> getDataset() {
        return dataset;
    }

    public void setDataset(List<InnerEntity> dataset) {
        this.dataset = dataset;
    }
}

public interface OuterTestRepository extends CrudRepository<OuterEntity, Long> {

    @Query("SELECT outerEntity FROM OuterEntity outerEntity LEFT JOIN outerEntity.dataset")
    Collection<OuterEntity> getAll();
}

@GetMapping("/test")
public ResponseEntity<?> validate() {
    return new ResponseEntity<>(repository.getAll(), HttpStatus.OK);
}

In the result of query OuterEntity host again contains reference on InnerEntity which initiate reference.

What is the common approach to prevent it?

Well, I return this result as is and web page shows me endless json. I didn't check the memory foot print. If this expected behaviour how to obtain result in traditional form? — Gleichmut, Mar 09 '20 at 11:39
Have a look at https://stackoverflow.com/questions/16577907/hibernate-onetomany-relationship-causes-infinite-loop-or-empty-entries-in-json. This might help and prevent infinite loop caused while generating json. — Madhusudana Reddy Sunnapu, Mar 09 '20 at 11:47
Nope, it's different things. Anyway, thank you for contribution! — Gleichmut, Mar 09 '20 at 11:54
The most common approach is not to create recursive relationships, as they're usually not necessary and they often just make things more complicated. — Kayaman, Mar 09 '20 at 11:56
If you use jackson for serialization consider using `@JsonManagedReference`, `@JsonBackReference` https://www.baeldung.com/jackson-bidirectional-relationships-and-infinite-recursion — Nonika, Mar 09 '20 at 11:59
Gleichmut you shouldn't return Entity to frontend. Map it first to Dto — Michal Cholewiński, Mar 09 '20 at 12:04

score 2 · Accepted Answer · answered Mar 09 '20 at 12:06

If you are using jackson you can use jacksons bidirectional mapping:

in OuterEntity:

@JsonManagedReference
@OneToMany(mappedBy = "host")
private List<InnerEntity> dataset = new ArrayList<>();

in InnerEntity:

@JsonBackReference
@ManyToOne(fetch = FetchType.LAZY)
private OuterEntity host;

Prevent recursive association in ManyToOne hibernate

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