Two way relationship with JsonBackReference & JsonManagedReference

问题

ANSWER

I'll solve my problem regarding to this blog Jackson – Bidirectional Relationships

Thanks you.

UPDATE 2

The problem is about JsonBackReference and JsonManagedReference annotations. With my two way relationship, I have to explicitly select one way for serialization with JsonBackReference and JsonManagedReference. But here, I am in case to use the opposit way "Parent->Child" for a specific requierement (using the way "Child->Parent" by default) When I inversed those two annotations, my JSON is what I'm looking for, for the special requierment. Any idea on how to use JACKSON in a two way relationship ?

Thank you.

UPDATE 1

Here is a code simple using EntityGraph (thanks to @NeilStockton suggestion), but still don't serialize the lazy attribute in JSON :-(

Parent

@Entity
public class Parent {
    @Id
    @GeneratedValue
    private Long id;

    @column
    private String parentAttribute;

    @OneToOne(mappedBy = "parent", optional = false)
    @JsonBackReference
    private Child child;

Child

@Entity
public class Child {
    @Id
    @GeneratedValue
    private Long id;

    @column
    private String childAttribute;

    @OneToOne(optional = false, cascade = CascadeType.ALL)
    @JsonManagedReference
    private Parent parent;

Parent Repository

public interface ParentRepository extends CrudRepository<Parent> {

    @EntityGraph(attributePaths = { "child" })
    //a hack to use findAll with default lazy/eager mapping
    Collection<Parent> findByIdNotNull(); 
}

Generated query :

Hibernate: 
    select
        parent0_.id as id1_33_0_,
        child1_.id as id1_32_1_,
        parent0_.parent_attribute as parent_attribute2_33_0_,
        child1_.child_attribute as child_attribute2_32_1_,
    from
        test.parent parent0_ 
    left outer join
        test.child child1_ 
            on parent0_.id=child1_.parent_id 
    where
        parent0_.id is not null

JSON (no child):

   [ {
    "id": 1
    "parentAttribute": "I am the parent"
    } ]

Any idea on how to force Jackson Hibernate4Module to serialize if present ? Thank you.

I have a Spring Boot 1.3.1 back-office using JPA/hibernate for mapping entities. The front-end is an Angular2 application. The communication is a REST/JSON. My question is about forcing EAGER loading in some queries when I have a Lazy relationship. The solution using JOIN FETCH helped me in DAO layer (Repositories). The entity is now completely loaded in a single query as I want in controllers layer. But the serialized JSON still incomplete due to Hibernate4Module.

Bellow Hibernate4Module features can't help :-(

FORCE_LAZY_LOADING
USE_TRANSIENT_ANNOTATION
SERIALIZE_IDENTIFIER_FOR_LAZY_NOT_LOADED_OBJECTS
REQUIRE_EXPLICIT_LAZY_LOADING_MARKER
REPLACE_PERSISTENT_COLLECTIONS

Any idea is welcome. Thanks.

回答1:

Finally, I solved my problem by using Custom Projection with a constructor in the select part of the query. In the new projection class, there is no "JsonIgnore" or any JPA annotation that make field not serialized by Jackson. I added more data in that projection for reach use. Hope it'll help.

来源：https://stackoverflow.com/questions/40268465/two-way-relationship-with-jsonbackreference-jsonmanagedreference

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java

spring-boot

jackson