Question:

I've implemented @ManyToMany mapping with an EmbeddedId class, as per the example provided by @Vlad Mihalcea. It works, however I need to create and use Spring's REST repository for this JoinTable Entity.

Usually, I would do something like this to enable the repository:

@CrossOrigin @RepositoryRestResource(collectionResourceRel = "companyproducts", path = "companyproducts") public interface CompanyProductRepository extends PagingAndSortingRepository<CompanyProduct, CompanyProduct.CompanyProductId> { }

But, since in this Entity (JoinTable) I don't have a classic id, like this:

public class FooBar { .... @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; ... }

but instead I have:

public class FooBar { .... @EmbeddedId private FooBarId id; ... }

I cannot use Long or let's say int because the identifier is not of any of those types, it's basically of type FooBarId.

By the way, I will also provide most of that class:

@Embeddable public class FooBarId implements Serializable { @Column(name = "foo_id") private Long fooId; @Column(name = "bar_id") private Long barId; private FooBarId() {} public FooBarId(Long fooId, Long barId) { this.fooId= fooId; this.barId= barId; } ... }

I did try, of course, putting FooBarId instead of Long in the repository declaration, but then in my REST json response I get something like this:

http://localhost:8080/api/foobar/com.example.springrest.entities.foobarid@g43

(note the path to the class itself, not a numeral parameter, eg. 5).

My question is: Is it possible to use repositories with an EmbeddedId instead of Long, int, etc.?

Yes of course

public interface FooBarRepository extends PagingAndSortingRepository<FooBar, FooBarId > { }

the id is the embeddable class so use that instead of the classic primitive.

the problem in the response is probably something related to your save/retrieve logic

<strong>Edit</strong>: based on the response being the class instead of the numeral i expect you retrieved the id from the repository, but you should obviously get the numerical value from the id since now that id is the embeddable class