Triple nested JPA Entity to JSON - Spring Boot Project-CodePudding

So, I have 3 @Entity classes

class Campaign
{
  @Id
  private long campaignId;
  //Other fields

  @OneToMany(mappedBy = "campaign",cascade=CascadeType.ALL)
    private Set<Question> questions;
}

class Question
{
  @Id
  private long questionId;

  //Other fields
  @OneToMany(mappedBy = "question",cascade=CascadeType.ALL)
    private Set<Choices> choices;

  @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="CAMPAIGN_ID")
    private Campaign campaign;
}

class Choices
{
  @Id
  private long choiceId;

  //Other fields
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="QUESTION_ID")
    private Question question;
}

When I create and send a JSON

{
    "campaignName" : "Dummy Quiz Campaign",
    "campaignDescription" : "This is a dummy quiz campaign for testing",
    "noOfQuestions":2,
    "noOfChoices":3,
    "lastUpdatedTime":"2012-04-23T18:25:43.511Z",
    "createdTime":"2012-04-23T18:25:43.511Z",
    "questions":[
        {
            "question":"Question 1",
            "choices":[
                {"choice":"Choice 1"},
                {"choice":"Choice 2"},
                {"choice":"Choice 3"}
                ],
            "correctAnswer":"Choice 2"
        },
        {
            "question":"Question 2",
            "choices":[
                {"choice":"Choice 4"},
                {"choice":"Choice 5"},
                {"choice":"Choice 6"}
                ],
            "correctAnswer":"Choice 2"
        }
    ]
}

It is being created and mapped accurately. It is also being deleted accurately.

But when I am trying to getAllCampaigns()

@GetMapping("/api/campaign/all")
    public List<Campaign> getAllCampaigns() throws Exception 
    {
        return campaignService.getAllCampaigns();
    }

It is showing a jackson.bind error, when I tried to write the JSON to a file, it ended up having an infinitely nested JSON.

What I can do to retrieve the Campaigns and there mapped entities like in the format I have send it.

As for the tables, 3 Tables Campaign Table Question Table with Campaign_Id Choices Table with Question_Id

Thanks in advance.

CodePudding user response：

The reason you are getting the infinite recursion is because, the question is mapped in the campaign class and the campaign is mapped in the question class. This bi-directional relation causes the infinite recursion. This can be solved by using @JsonManagedReference, and @JsonBackReference annotations on the mappings. You can use the @JsonManagedRefernce annotation on the one to many relation and @JsonBackReference annotation on the Many to one relation. This should solve the recursion problem. You can get more info from here . Let me know if this helps.

CodePudding user response：

Here you need to add @JsonIgnore Anotation like this:

class Question{
@Id
private long questionId;

//Other fields
@OneToMany(mappedBy = "question",cascade=CascadeType.ALL)
private Set<Choices> choices;

@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(name="CAMPAIGN_ID")
@JsonIgnore
private Campaign campaign;
}