Custom gson deserializer

PayoutDetailsResponseDeserializer.java

package com.messapps.carpo.network.custom_converters;

import android.support.annotation.Nullable;

import com.google.gson.Gson;
import com.google.gson.JsonArray;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.messapps.carpo.components.objects.payout.JsonFunding;
import com.messapps.carpo.components.objects.payout.JsonIndividual;
import com.messapps.carpo.components.objects.payout.JsonPayout;
import com.messapps.carpo.network.responses.payment.PayoutDetailsResponse;

import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Custom converter for {@link PayoutDetailsResponse}
 * We have some troubles with backend response typing and the app is already live, so we can not
 * change the response as we please
 */
public final class PayoutDetailsResponseDeserializer
        implements JsonDeserializer<PayoutDetailsResponse> {

    Gson mGson;

    public PayoutDetailsResponseDeserializer() {
        super();
        mGson = new Gson();
    }

    /**
     * Gson invokes this call-back method during deserialization when it encounters a field of the
     * specified type.
     * <p>In the implementation of this call-back method, you should consider invoking
     * {@link JsonDeserializationContext#deserialize(JsonElement, Type)} method to create objects
     * for any non-trivial field of the returned object. However, you should never invoke it on the
     * the same type passing {@code json} since that will cause an infinite loop (Gson will call your
     * call-back method again).
     *
     * @param json    The Json data being deserialized
     * @param typeOfT The type of the Object to deserialize to
     * @param context
     * @return a deserialized object of the specified type typeOfT which is a subclass of {@code T}
     * @throws JsonParseException if json is not in the expected format of {@code typeofT}
     */
    @Override
    public PayoutDetailsResponse deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {
        PayoutDetailsResponse result = new PayoutDetailsResponse();
        JsonObject response = json.getAsJsonObject();
        //retrieve status code
        result.statusCode = response.getAsJsonPrimitive("statusCode").getAsString();

        //retrieve errors list, if errors - return empty list
        try {
            List<String> errors = new ArrayList<>(2);
            JsonArray array = response.get("errors").getAsJsonArray();
            for (JsonElement element : array) {
                String error = element.getAsString();
                errors.add(error);
            }
            result.errors = errors;
        } catch (IllegalStateException ise) {
            result.errors = Collections.emptyList();
        }

        //retrieve a message
        result.message = response.getAsJsonPrimitive("message").getAsString();

        //retrieve payout object
        result.result = getPayout(response.get("result").getAsJsonObject());

        return result;
    }

    /**
     * Parse payout object
     *
     * @param input
     * @return
     */
    private JsonPayout getPayout(JsonObject input) {
        JsonPayout result = JsonPayout.createForJsonParser();
        result.setMerchantId(input.getAsJsonPrimitive("merchantId").getAsString());
        result.setStatus(input.getAsJsonPrimitive("status").getAsString());
        result.setIndividual(getIndividual(input.get("individual").getAsJsonObject()));
        result.setFunding(getFunding(input.get("funding").getAsJsonObject()));
        return result;
    }

    /**
     * Converts provided {@link JsonObject} into {@link JsonIndividual}
     *
     * @param input json source
     * @return parsed {@link JsonIndividual} or <bold>null</bold>
     */
    @Nullable
    private JsonIndividual getIndividual(JsonObject input) {
        JsonIndividual individual;
        try {
            individual = mGson.fromJson(input, JsonIndividual.class);
        } catch (Exception e) {
            //we can not recover from any exception here, just return null
            individual = null;
        }
        return individual;
    }

    /**
     * Converts provided {@link JsonObject} into {@link JsonFunding}
     *
     * @param input json source
     * @return parsed {@link JsonFunding} or <bold>null</bold>
     */
    @Nullable
    private JsonFunding getFunding(JsonObject input) {
        JsonFunding funding;
        try {
            funding = mGson.fromJson(input, JsonFunding.class);
        } catch (Exception e) {
            //we can not recover from any exception here, just return null
            funding = null;
        }
        return funding;
    }
}