Spring Data REST and IdClass - not compatible?

Question

I am trying to use Spring Data REST with a given SQL schema, which uses the JPA @IdClass annotation for associative tables (intersection table, or many-to-many resolution table). These mapping entities do not get serialized properly.

I created a small project, that illustrates the problem. It's a fork of spring-data-examples, and pretty straightforward. It is using eclipselink, but I already tested it with Hibernate and the problem is the same.

https://github.com/otrosien/spring-data-examples/tree/idClassFailureWithSerializable

The setup: 2 entities: Customer and Relationship, 2 repositories: CustomerRepository, RelationshipRepository, both extend CrudRepository

Customer has a generated Id, and firstname, lastname as String. Relationship has the IdClass "RelationshipID" and customer1, customer2 as composite primary key, both having foreign key on Customer. Plus a relation string.

A basic integration test shows the entities work as expected.

Customer dave = customers.save(new Customer("Dave", "Matthews"));
Customer jack = customers.save(new Customer("Jack", "Johnson"));

assertThat(customers.findOne(dave.getId()), is(dave));
assertThat(customers.findOne(jack.getId()), is(jack));

Relationship rel = relationships.save(new Relationship(dave, jack, "likes"));
assertThat(relationships.findOne(rel.pk()), is(rel));

So far so good. Let's try this via REST API now.

POST http://localhost:8080/customers
Content-Type: application/json

{
  "lastname" :"Dave",
  "firstname":"Matthews"
}

POST http://localhost:8080/customers
Content-Type: application/json

{
  "lastname" :"Jack",
  "firstname":"Johnson"
}

POST http://localhost:8080/relationships
Content-Type: application/json

{
  "customer1" : "http://localhost:8080/customers/1",
  "customer2" : "http://localhost:8080/customers/2",
  "relation" : "likes"
}

I always get a 201 Created, which is good. But the representation of the mapping entity looks broken. Instead of proper links they seem to be serialized objects.

GET /relationships

200 OK
{
  "_embedded" : {
    "relationships" : [ {
      "relation" : "likes",
      "_links" : {
        "self" : {
          "href" : "http://localhost:8080/relationships/Customer%20%5Bid=2,%20firstname=F,%20lastname=L%5D"
        },
        "customer1" : {
          "href" : "http://localhost:8080/relationships/Customer%20%5Bid=2,%20firstname=F,%20lastname=L%5D/customer1"
        },
        "customer2" : {
          "href" : "http://localhost:8080/relationships/Customer%20%5Bid=2,%20firstname=F,%20lastname=L%5D/customer2"
        }
      }
    } ]
  }
}

Question: Has anyone succeeded in using Spring Data REST with mapping entities? Can you spot a mistake in the implementation? Or is it a bug? (I'm using spring boot 1.2.4.RELEASE with starter-data-rest and starter-data-jpa, which should all be the latest releases)

Please, no suggestions to change the schema. I already know I can fix it by inserting a generated @Id into Relationship, but the schema is given as-is.

Answer 1

I solve the problem by custom BackendIdConverter.

spring data rest with composite primary key

Hope this will help you.