Question

I am new to Play framework and yml notation, and know just the basics for Hibernate. I am trying to set up some test data by using a .yml file. I try to define several Question objects and an ActiveCompetition object that refer to the same Competition object. My .yml file looks like this (I have removed what I think is not relevant):

ActiveCompetition(1): &myactivecompetition
    activeCompetition: &mycompetition
        name: Name of the competition

Question(11):
    title: Title 1
    competition: *mycompetition

Question(12):
    title: Title 2
    competition: *mycompetition

Question(13):
    title: Title 3
    competition: *mycompetition

I works, but it seems that Hibernate saves *mycompetition 4 times.

In the java beans the attributes for javax.persistence are set as follows:

@Entity
@Transactional
public class ActiveCompetition extends Model {

   @Required
   @OneToOne(cascade= CascadeType.ALL)
   private Competition activeCompetition;
}

@Entity
@Transactional
public class Question extends Model {

    ...

    @Required
    @OneToOne(cascade= CascadeType.ALL)
    private Competition competition;
}

How do I make Hibernate understand that *mycompetition should be stored only once in the database? Should I write the database id on the .yml file? If so, how do I do this? I have tried already to add for example ‘id: 99’ under activeCompetition but it doesn’t help.

Answer 1

There are two possible issues:

First one is that you are declaring the relatiosn OneToOne, but then in your YAML file you create a ManyToOne relation. OneToOne means that each ActiveCompetition has, at most, one question, and each Question relates to, at most, one ActiveCompetition.

What you you want is a ManyToOne relation where an ActiveCompetition has many Question. You should update your Java code.

Second one is that you are defining your ActiveCompetition as:

ActiveCompetition(1)

In YAML, AFAIK, you reference other entities in the file by the reference provided with the entity (or that’s how I did it). In the declaration above the reference is the number 1 between ().

So you should change your file to:

Question(13):
    title: Title 3
    competition: 1