When an association resource is not exported (e.g. @RestResource(exported = false)), custom links (RepresentationModelProcessor) are not handled properly. [DATAREST-1488]

jvanheesch opened DATAREST-1488 and commented

This issue was discussed in https://gitter.im/spring-projects/spring-data.

Please see reference url for quick reproducer.

I defined two aggregate roots: Car and Engine.
Car has an engine.
I then chose not to export this association resource (@RestResource(exported = false)).
This modifies car's representation (in both collection resource and item resource): it removes the engine link and inlines engine as a regular property.
However, in the resulting json, engine has a _links property, which is invalid HAL.
Example: GET to http://localhost:8080/cars/2 returns

{
  "name": "carName",
  "engine": {
    "name": "engineName",
    "_links": {
      "engineLink": {
        "href": "http://www.google.com"
      }
    }
  },
  "_links": {
    "self": {
      "href": "http://localhost:8080/cars/2"
    },
    "car": {
      "href": "http://localhost:8080/cars/2"
    }
  }
}

EDIT: I just realised the same holds for _embedded: both _embedded and _links of an association resource are rendered when the association resource is not exported.
I created a new branch EnginePart.
I created an Entity EnginePart, which has an excerptProjection that renders its name.
Engine now has a @OneToOne EnginePart.

GET http://localhost:8080/cars/3 now returns the following json:

{
  "name": "carName",
  "engine": {
    "name": "engineName",
    "_embedded": {
      "enginePart": {
        "name": "enginePartName",
        "_links": {
          "self": {
            "href": "http://localhost:8080/engineParts/1{?projection}",
            "templated": true
          }
        }
      }
    },
    "_links": {
      "engineLink": {
        "href": "http://www.google.com"
      },
      "enginePart": {
        "href": "http://localhost:8080/engineParts/1{?projection}",
        "templated": true
      }
    }
  },
  "_links": {
    "self": {
      "href": "http://localhost:8080/cars/3"
    },
    "car": {
      "href": "http://localhost:8080/cars/3"
    }
  }
}

I believe both _links and _embedded should only be present as "top level properties" in valid HAL.

TL;DR: when inlining an association resource, only its content should be included, not its _links and _embedded.

Reference URL: https://github.com/jvanheesch/spring-data-rest-inlined-resource-custom-links