Realm, GSON and primitive JSON arrays

CustomTypeAdapter.java

// Make a custom Gson instance, with a custom TypeAdapter for each wrapper object.
// In this instance we only have RealmList<RealmInt> as a a wrapper for RealmList<Integer>
Type token = new TypeToken<RealmList<RealmInt>>(){}.getType();
Gson gson = new GsonBuilder()
        .setExclusionStrategies(new ExclusionStrategy() {
            @Override
            public boolean shouldSkipField(FieldAttributes f) {
                return f.getDeclaringClass().equals(RealmObject.class);
            }

            @Override
            public boolean shouldSkipClass(Class<?> clazz) {
                return false;
            }
        })
        .registerTypeAdapter(token, new TypeAdapter<RealmList<RealmInt>>() {

            @Override
            public void write(JsonWriter out, RealmList<RealmInt> value) throws IOException {
                // Ignore
            }

            @Override
            public RealmList<RealmInt> read(JsonReader in) throws IOException {
                RealmList<RealmInt> list = new RealmList<RealmInt>();
                in.beginArray();
                while (in.hasNext()) {
                    list.add(new RealmInt(in.nextInt()));
                }
                in.endArray();
                return list;
            }
        })
        .create();

// Convert JSON to objects as normal
List<MainObject> objects = gson.fromJson(json, new TypeToken<List<MainObject>>(){}.getType());

// Copy objects to Realm
realm.beginTransaction();
realm.copyToRealm(objects);
realm.commitTransaction();

example.json

[
    { "name"  : "Foo",
      "ints" : [1, 2, 3]
    },
    { "name"  : "Bar",
      "ints" : []
    }
]  

MainObject.java

public class MainObject extends RealmObject {

    private String name;
    private RealmList<RealmInt> ints;

    // Getters and setters
}

RealmInt.java

public class RealmInt extends RealmObject {
    private int val;

    public RealmInt() {
    }

    public RealmInt(int val) {
        this.val = val;
    }

    // Getters and setters
}

Don't we need to define primary key for RealmInt ? so it does not overwrite. Consider i have two RealmList in Model and they have same values, then i want to change one of the list's value and leave other RealmList same, is this possible with this implementation? @cmelchior

if the primitive array can be null you might want to add this check to your read method:

if (in.peek() == JsonToken.NULL) {
   in.nextNull();
   return null;
}

This was very helpful, thank you.

👍

@cmelchior any workaround if we use realm.createOrUpdateObjectFromJson(RecipeRealmObject.class, jsonObject) method.
I am getting the following exception:
org.json.JSONException: Value Sätt ugnen på knappt 225 grader. Smörj en ugnsfast form som ska vara så liten att fiskblocket ligger trångt och ha kanter som går minst någon cm över fiskens höjd. at 0 of type java.lang.String cannot be converted to JSONObject
at org.json.JSON.typeMismatch(JSON.java:100)

I have a json object as : {"recipe":{ "name":"Recipe name", cookingSteps": [
"Sätt ugnen på 175 grader.",
"Lägg kycklingfiléerna i en ugnsfast form. \r\nBlanda ihop ingredienserna till såsen och häll sedan över kycklingen.",
"Laga i mitten av ugnen i ca. 60 min.\r\n\r\nFantastiskt enkelt och gott:)"
]}}

Any help would be greatly appreciated.

I am facing the same problem about java.lang.String cannot be converted to JSONObject
at org.json.JSON.typeMismatch(JSON.java:100)

any workaround?

@cmelchior, @RajendraSinghBohra : I have created a solution which will work fine without having issue as mentioned in previous comments.

https://gist.github.com/Joisar/72629f74b3da368ca34b358e91bd34e7

How can this be used for ArrayList<ArrayList> ?

I have a field like this : @SerializedName("matches") private ArrayList<ArrayList> matches;

@cmelchior/@Joisar/ @RajendraSinghBohra, Plz pardon my ignorance..
I am using retrofit and gson to process my response. I'm using it this way:

Gson gson = new GsonBuilder()
.create();

        retrofit = new Retrofit.Builder()
                .baseUrl(Res.string(R.string.appconfig_api_base_url))
                .addConverterFactory(GsonConverterFactory.create(gson))
                .client(builder.build())
                .build();

Now in one of my APIs with large json structure, there are a couple of primitive arrays- String and ints.
By using the above workaround to convert these primitives, do I have to process the rest of the response elements with the same custom type adapter? or can I just process the primitive arrays with this method? I'm not sure how to take just the portion of json structure and input it to the deserializer and process rest of them with my default gson.

Thanks in advance..

Nevermind, I figured it out myself..
instead of using default gson builder, I used like below:

 Gson gson = RealmParserUtil.getGson();
        retrofit = new Retrofit.Builder()
                .baseUrl(Res.string(R.string.appconfig_api_base_url))
                .addConverterFactory(GsonConverterFactory.create(gson))
                .client(builder.build())
                .build();

My Custom RealmParser:

public class RealmParserUtil {
    public static Gson getGson(){
        Gson gson = new GsonBuilder()
                .setLenient()
                .setExclusionStrategies(new ExclusionStrategy() {
                    @Override
                    public boolean shouldSkipField(FieldAttributes f) {
                        return f.getDeclaringClass().equals(RealmObject.class);
                    }


                    @Override
                    public boolean shouldSkipClass(Class<?> clazz) {
                        return false;
                    }
                })
                .create();
        return gson;
    }


    public static String serialize(Object object) {
        return getGson().toJson(object);
    }

    public static Object deserialize(String objectString, Type type) {
        Log.i("SuperCustomer", "Deserializing json response");
        return getGson().fromJson(objectString, type);
    }


    public static class ArrayToStringTypeAdapter extends TypeAdapter<RealmList<RealmString>> {

        @Override
        public void write(JsonWriter out, RealmList<RealmString> value) throws IOException {
            //out.value(String.valueOf(value));
        }

        @Override
        public RealmList<RealmString> read(JsonReader in) throws IOException {
            RealmList<RealmString> list = new RealmList<RealmString>();

            boolean isArray = (in.peek() == JsonToken.BEGIN_ARRAY);

            if(isArray) {
                in.beginArray();
                while (in.hasNext()) {
                    list.add(new RealmString(in.nextString()));
                }
                in.endArray();
            }
            return list;
        }
    };
}

In my model class I used this:

    @JsonAdapter(RealmParserUtil.ArrayToStringTypeAdapter.class)
    private RealmList<RealmString> strInterests;

Thank you @Joisar for your gist, it helped me a lot.

@cmelchior
I implemented your solution but its not working for me. Do you have an update code for parsing primitive array string or int?
thanks!