MongoDB Nested objects with own Repository interface

Question

I am using Spring Data MongoDB to load and save some simple domain classes. As a simple example lets say I have Factory and Product

@Document
public class Factory {
    @Id String id;
    String name;
    List<Product> products;
}

@Document
public class Product {
    @Id String id;
    String name;
    Date productionDate;
}

Ok, simple enough I can now create a FactoryRepository:

public interface FactoryQueryRepository extends MongoRepository<Factory, String> {}

This repository already has basic CRUD functionality to store and load Factories together with nested products. Now lets say I want to only retrieve a set of products for a given factory.

I now have two questions:

A) Can I somehow return a list of products instead of a list of factories in the FactoryQueryRepository like so:

@Query(value = "???")
public List<Product> findProductByFactoryName(String name);

B) Lets say my factory does not only have products but also employees, customers, suppliers, you name it ... Now if need to define a few special query methods for each of these nested collections then I soon end-up with a very big FactoryQueryRepository interface. So it would actually be more appropriate to create a new ...QueryRepositoy for Product, Employee, Customer and so on. But when I try to do this, it seems it only works if I first save a stand alone Product object that is not nested inside a Factory. Is there a way that I can (similar to question A) define a ProductQueryRepository interface and use it to retrieve all Products that are nested inside a Factory by specifying some filter criteria of the Factory, something like this:

public interface ProductQueryRepository extends MongoRepository<Product, String> {
    @Query(/* select products from factory where name = '?0' */)
    public List<Product> findProductsByFactoryName(String name);
}

Shoud I in this case rather make use of the @DBRef than to use nested objects?

fullstackdev · Accepted Answer · 2015-01-06 03:48:59Z

1

For your question A) - you should use MongoTemplate to write a custom query.

For your question B) you should try to avoid any references when using MongoDB. MongoDB only guarantees atomic writes on a single document, not across multiple documents. If you must use a reference then you should not use DBRef, you should implement the reference manually (this is mentioned explicitly in the docs http://docs.mongodb.org/manual/reference/database-references/)

answered Jan 6, 2015 at 3:48

fullstackdev

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