Gson 工具类

工具类主体

public class GsonUtil {

    private static Gson gson = new GsonBuilder()
            .registerTypeAdapter(Integer.class, new IntegerDefault0Adapter())
            .registerTypeAdapter(int.class, new IntegerDefault0Adapter())
            .registerTypeAdapter(Double.class, new DoubleDefault0Adapter())
            .registerTypeAdapter(double.class, new DoubleDefault0Adapter())
            .registerTypeAdapter(Long.class, new LongDefault0Adapter())
            .registerTypeAdapter(long.class, new LongDefault0Adapter())
            .create();

    public static String toJson(Object value) {
        return gson.toJson(value);
    }

    public static <T> T fromJson(String json, Class<T> classOfT) throws JsonParseException {
        return gson.fromJson(json, classOfT);
    }

    public static <T> T fromJson(String json, Type typeOfT) throws JsonParseException {
        return (T) gson.fromJson(json, typeOfT);
    }
}

注册类型适配器（int 举例）

public class IntegerDefault0Adapter implements JsonSerializer<Integer>, JsonDeserializer<Integer> {
    @Override
    public Integer deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        try {
            if (json.getAsString().equals("") || json.getAsString().equals("null")) {//定义为int类型,如果后台返回""或者null,则返回0
                return 0;
            }
        } catch (Exception ignore) {
        }
        try {
            return json.getAsInt();
        } catch (NumberFormatException e) {
            throw new JsonSyntaxException(e);
        }
    }

    @Override
    public JsonElement serialize(Integer src, Type typeOfSrc, JsonSerializationContext context) {
        return new JsonPrimitive(src);
    }
}