Get parents from JSON when using polymorphic associations

Question

Is there an elegant way to work with JSON response when using polymorphic associations in the below example?

JSON response:

[
  {
    "created_at":"2017-12-13T10:37:36Z",
    "id":16,
    "parent_id":21,
    "parent_type":"app.models.Site",
    "store_number":"0070004900049",
    "updated_at":"2017-12-13T10:37:36Z",
    "value":"fake value",
    "parents":{
      "sites":[
        {
          "created_at":"2017-12-13T10:37:36Z",
          "id":21,
          "section_id":21,
          "updated_at":"2017-12-13T10:37:36Z"
        }
      ]
    }
  }
]

I have 3 models: Parameter as a polymorphic model, with parent_id and parent_type columns, Site.

Here is how I'm truing to test JSON response in ParametersControllerSpec:

Map[] siteSettingsMaps = JsonHelper.toMaps(responseContent());
the(siteSettingsMaps.length).shouldBeEqual(1);
Map siteSetting = siteSettingsMaps[0];

the(siteSetting.get("value")).shouldBeEqual("fake value");
the(siteSetting.get("store_number")).shouldBeEqual(STORE_NUMBER);

It is OK till now. But how to extract parents map ? When I tried like that:

Map<String, Map []> parents = (Map<String, Map []>)siteSettingsMaps[0].get("parents");
Map[] sites = parents.get("sites");
Map site = sites[0];

I got ava.lang.ClassCastException: java.util.ArrayList cannot be cast to [Ljava.util.Map;. Why isn't it a Map ? Should I cast to a List ? I didn't find any methods like getParents(), for example, there is only setter for that. Thank you.

Answer 1

It is simpler than you think. At this point, it is a matter of working with JSON, which has no type, other than Map and List:

Map[] siteSettingsMaps = JsonHelper.toMaps(x);
the(siteSettingsMaps.length).shouldBeEqual(1);
Map siteSetting = siteSettingsMaps[0];

the(siteSetting.get("value")).shouldBeEqual("fake value");
the(siteSetting.get("store_number")).shouldBeEqual("0070004900049");

Map parents = (Map) siteSetting.get("parents");
List<Map> sites = (List<Map>) parents.get("sites");
the(sites.size()).shouldBeEqual(1);

The JsonHelper is there for convenience to run tests. You can get really fancy with Jackson or any other JSON library if you like. I generally stay within JavaLite, as this is sufficient.