Add multi level relations loading support

[sverin]

I having an issue when I fetching objects that have relationship in more than one level. I have 3 different classes that reference to each other by a one-to-one relationship, as shown below.

@Document(collection = "products")
@TypeAlias(value = "product")
public class Product {
  
  @Id
  private String id;

  private String name;

  @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
  @JoinProperty(name = "variations")
  private List<ProductVariation> variations;

}

@Document(collection = "variations")
@TypeAlias(value = "variation")
public class ProductVariation {

  @Id
  private String variationId;

  private String name;

  @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
  @JoinProperty(name = "options")
  private List<Option> options;

}

@Document(collection = "options")
@TypeAlias(value = "option")
public class Option {

  @Id
  private String optionId;

  private String text;

}

Through a spring-controller and spring repository I can add some data to MongoDB database. But then my issue starts. As you can see in the repsonse below the option does not have any text value when I use a ProductRepository to fetch the data. I have checked the MongoDB database and the data has been saved correctly.

[
  {
    "id": "5ef4998e0a994e434d6cce86",
    "name": "My Product Name",
    "variations": [
      {
        "id": "5ef4998e0a994e434d6cce84",
        "name": "My Product Variation Name",
        "options": [
          {
            "id": "5ef4998e0a994e434d6cce88",
            "text": null
          }
        ]
      }
    ]
  }
]

However, if I use a ProductVariationRepository and do the fetch one level down, it works perfectly.

[
  {
    "id": "5ef4998e0a994e434d6cce84",
    "name": "My Product Variation Name",
    "options": [
      {
        "id": "5ef4998e0a994e434d6cce88",
        "text": "My options value"
      }
    ]
  }
]

Is this a bug? Can't you have multi level relationship? Or have I missed something in my configuration ?

[sverin]

Thank you for your quick response. Its a great library, and this would make it even better.

[kaiso]

Hello @sverin I've published a release candidate version 3.4.0-RC1 to address the multi level loading feature.
can your test and give me your feedback please?
Thank you

[sverin]

I have tried it today and it works perfectly. It all works as I expected now. I will try it out some more until friday and if I have some issues I'll let you know. Thanks for your quick response. This framework just become even better.

[sverin]

I have tried it now for a couple of days and it works fine. If you feel comfortable with the code you can close the issue and make a final release.

[kaiso]

Thank you @sverin I will release the version then.

[loehnertz]

@sverin
I have almost exactly the same setup as you posted in your first comment above.
The only differences are that I have @OneToOne relations and that I am using Kotlin instead of Java (I don't think this causes a problem in this particular case, but it could potentially).
Apart from that, it's the same. I am running on v3.4.1. I also have three collections with the same nesting structure.
However, I cannot get it to work. For me, all fields are null when loaded out of MongoDB again. To me, it looks like the relation is never resolved after some debugging deep in Spring Data (spring-data-commons-2.3.5) (I receive a MappingInstantiationException). The persisting works just fine. With only one level of relation, it also works perfectly.

When you wrote:

I have tried it today and it works perfectly. It all works as I expected now.

Did you refer to the same setup as you posted initially or did you change some details afterward in your running solution?