SpringBoot - 关系的实体传播

Question

I have two entities: WorkoutTemplate and ConcreteExercise.

In WorkoutTemplate I have this relationship with ConcreteExercises

@OneToMany(cascade = CascadeType.ALL, mappedBy = "belongingWorkout", fetch = FetchType.LAZY)
private List<ConcreteExercise> concreteExercises;

And in ConcreteExercise I have this relationship with WorkoutTemplate

@ManyToOne
private WorkoutTemplate belongingWorkout;

I would like to insert a WorkoutTemplate into my database... I make the request to the controller sending a Json like this:

{ "workoutName" : "My Workout",
concreteExercises: [
   {
"name" : "Squat"
   } 
 ]
}

The DAO insert into my DB the WorkoutTemplate And insert also in the table of the ConcreteExercise the name. But not the reference to the WorkoutTemplate... Practically, the table ConcreteExercise is made of:

id, name, belongin_workout_id

With the request above, we populate the id (auto-increment) and the name, but not the foreign key to the WorkoutTemplate.

How can I solve this? I would like to automatically insert the foreign key without sending it in the request or doing it manually into the service

Answer 1

Hi there it's because you are not using @JoinColumn which marks a column for as a join column for an entity association or an element collection.

On your WorkoutTemplate entity - you can retain this:

@OneToMany(cascade = CascadeType.ALL, mappedBy = "belongingWorkout", fetch = FetchType.LAZY)
private List<ConcreteExercise> concreteExercises;

But on your ConcreteExercise entity - you need to have this change:

@ManyToOne
@JoinColumn(name = "workout_template_id", nullable = false)
private WorkoutTemplate belongingWorkout;

The above code will create a foreign key linking the ConcreteExercise entity with the primary key from the WorkoutTemplate entity. The name of the foreign key column in the ConcreteExercise entity is specified by name property which for this case is workout_template_id - feel free to change this.

If you have set this up but still not working, it will also be helpful to share a code snippet on how are you saving these.