Question

由于Realm无法使用包含String的促销类型，我试图像in this question一样实施JsonDeserializer。

问题是我为什么会收到以下错误感到困惑：

W / System.err：com.google.gson.JsonSyntaxException：java.lang.IllegalStateException：预期为BEGIN_OBJECT但是为STRING

这是Json的一部分："tags": ["GLUTEN FREE", "NUT FREE"],

My RealmString：

public class RealmString extends RealmObject {
    private String value;

    public RealmString() {
    }

    public RealmString(String value) {
        this.value = value;
    }

    public String getValue() {
        return value;
    }

    public void setValue(String value) {
        this.value = value;
    }
}

部分改装的Pojo：

public class Entity extends RealmObject {

    @SerializedName("tags")
    private RealmList<RealmString> tags = null;
}

..和解串器：

public class StringRealmListConverter implements JsonDeserializer<RealmList<RealmString>> {

    @Override
    public RealmList<RealmString> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {

        RealmList<RealmString> realmStrings = new RealmList<>();
        JsonArray ja = json.getAsJsonArray();
        for (JsonElement je : ja) {
            realmStrings.add((RealmString) context.deserialize(je, RealmString.class));
        }

        return realmStrings;
    }
}

我在这里注册：

public Gson provideGson() {
    return new GsonBuilder()
            .registerTypeAdapter(Food.class, new FoodDeserializer())
            .registerTypeAdapter(new TypeToken<RealmList<RealmString>>() {}.getType(),
                    new StringRealmListConverter())
            .create();
}

编辑这是FoodDeserializer。它处于这种混乱状态，因为我们不得不使用Composition over Inheritance来取悦Realm众神：

public class FoodDeserializer implements JsonDeserializer<Food> {
    public static final String TAG = FoodDeserializer.class.getSimpleName();

    Gson mHelperGson;

    public FoodDeserializer() {
        mHelperGson = new GsonBuilder().create();
    }

    @Override
    public Food deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        String type = json.getAsJsonObject().get("responseType").getAsString();
        switch (type) {
            case "Platter":
                return parsePlatter(json);
            case "FoodItem":
                return parseFoodItem(json);
            default:
                return null;
        }
    }

    private PlatterEntity parsePlatter(JsonElement json) {

        FoodEntity food = mHelperGson.fromJson(json, new TypeToken<FoodEntity>() {
        }.getType());

        ArrayList<FoodItemEntity> items = new ArrayList<>();
        JsonElement je1 = json.getAsJsonObject().get("items");
        if (je1 != null) {
            JsonArray list = je1.getAsJsonArray();
            if (list != null) {
                items = mHelperGson.fromJson(list.toString(), new TypeToken<List<FoodItemEntity>>() {
                }.getType());
            }
        }

        return new PlatterEntity(food, items);
    }

    private FoodItemEntity parseFoodItem(JsonElement json) {

        FoodEntity food = mHelperGson.fromJson(json, new TypeToken<FoodEntity>() {
        }.getType());

        Boolean readyToEat = null;
        JsonElement je1 = json.getAsJsonObject().get("readyToEat");
        if (je1 != null) {
            readyToEat = je1.getAsBoolean();
        }

        String heatingInstructions = null;
        JsonElement je2 = json.getAsJsonObject().get("heatingInstructions");
        if (je2 != null) {
            heatingInstructions = je2.getAsString();
        }

        ArrayList<IngredientEntity> ingredients = new ArrayList<>();
        JsonElement je3 = json.getAsJsonObject().get("ingredients");
        if (je3 != null) {
            JsonArray list = je3.getAsJsonArray();
            if (list != null) {
                ingredients = mHelperGson.fromJson(list.toString(), new TypeToken<List<IngredientEntity>>() {
                }.getType());
            }
        }

        NutritionEntity foodNutritions = mHelperGson.fromJson(json, new TypeToken<NutritionEntity>() {
        }.getType());

        return new FoodItemEntity(food, readyToEat, heatingInstructions, ingredients, foodNutritions);
    }
}

我想使用JsonDeserializer而不是TypeAdapter，但感谢任何帮助，谢谢！

Answer 1

原来我的感觉是对的。我必须将StringRealmListConverter添加到FoodDeserializable构造函数中，如下所示：

    public FoodDeserializer() {
        mHelperGson = new GsonBuilder()
            .registerTypeAdapter(new TypeToken<RealmList<RealmString>>() {
                    }.getType(),
                    new StringRealmListConverter())
            .create();
    }

Answer 2

您可以使用JsonDeserializationContext（作为deserialize函数的第二个参数传递）正确反序列化RealmString。 context知道如何反序列化使用当前Gson实例注册的所有自定义类型。请参阅此处JsonDeserializationContext的文档：https://google.github.io/gson/apidocs/com/google/gson/JsonDeserializationContext.html。

它不能使用您当前的代码的原因是因为您在FoodDeserializer中创建了一个新的 Gson实例，而该实例并不知道RealmString的自定义反序列化器。

将RealList <realmstring>反序列化为List <string>时出错

2 个答案: