Infinite loop with spring-boot in a one to many relation

Question

In a rest application, I use spring boot with jpa.

I have a class Lodger

who have

@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "lodger")
private List<Reference> referenceList;

In my class Reference, i have

@ManyToOne
@JoinColumn(name = "lodgerId")
private Lodger lodger;

when i call this method

@RequestMapping(value = "/lodgers/{lodgerId}", method = RequestMethod.GET)
public Lodger getLogderById(@PathVariable("lodgerId") long lodgerId) {
    return lodgerService.getLodger(lodgerId);
}

I get this error

org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: Infinite recursion (StackOverflowError) (through reference chain: server.bean.Lodger["referenceList"]->org.hibernate.collection.internal.PersistentBag[0]->server.bean.Reference["lodger"]->server.bean.Lodger["referenceList"]->org.hibernate.collection.internal.PersistentBag[0]->server.bean.Reference["lodger"]->server.bean.Lodger["referenceList"]...

Answer 1

Solution:

Use

@JsonManagedReference annotation for the first objects instantiated

@JsonBackReference annotation for the second objects instantiated

First:

@JsonManagedReference
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "lodger")
    private List<Reference> referenceList;

Second:

@JsonBackReference
@ManyToOne
    @JoinColumn(name = "lodgerId")
    private Lodger lodger;

Answer 2

Do not return entity with circular dependencies via REST webservice - create new DTO class, map entities fetched from database and return it in webservice.

More info here: http://www.baeldung.com/entity-to-and-from-dto-for-a-java-spring-application

Of course if you want you may use another mapping library, my personal favourite is Orika (http://orika-mapper.github.io/orika-docs/intro.html)

Answer 3

If you primary keys in both tables are same name for example : id.

Add this

@Entity
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class,property = "id")
public class User {
    ...
}

And to Reference class.

@Entity
@JsonIdentityInfo(generator = ObjectIdGenerators.PropertyGenerator.class,property = "id")
public class Reference {
    ...
}

Answer 4

The only thing that you need is, in your class in which you have the annotation @ManyToOne, implement the next annotation with the attributes that you want to skip in the value section @JsonIgnoreProperties(value = {"yourAttribute", "handler", "hibernateLazyInitializer"}, allowSetters = true)

I put an example for your code ->

@ManyToOne(fetch = FetchType.LAZY)
@JsonIgnoreProperties(value = {"referenceList", "handler","hibernateLazyInitializer"}, allowSetters = true)
@JoinColumn(name = "lodgerId")
private Lodger lodger;

All the attributes that you put in the value section on the @JsonIgnoreProperties are ignored, with this you can resolve the infinite loop and use it for other developments with the same format in the future.