Question

我正在尝试使用Gson反序列化JSONArray，其中一个值的类型可能会有所不同，值“in_wanted”可以是boolean或JSONObject。

in_wanted as boolean：

{
"movies": [
        {
            "title": "example boolean",
            "in_wanted": false
        }
    ]           
}

in_wanted as JSONObject：

{
"movies": [
        {
            "title": "example object",
            "in_wanted": {
                "profile": {
                    "value": false
                }
            }
        }
    ]           
}

我需要对象，只要它可用，我需要一个反序列化器，只要“in_wanted”的值是布尔值，就返回null。用Gson做最好的方法是什么？

Answer 1

您可以使用自定义反序列化器执行此操作。在开始时，我们应该创建可以代表您的JSON的数据模型。

class JsonEntity {

    private List<Movie> movies;

    public List<Movie> getMovies() {
        return movies;
    }

    public void setMovies(List<Movie> movies) {
        this.movies = movies;
    }

    @Override
    public String toString() {
        return "JsonEntity [movies=" + movies + "]";
    }
}

class Movie {

    private String title;
    private Profile in_wanted;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Profile getIn_wanted() {
        return in_wanted;
    }

    public void setIn_wanted(Profile in_wanted) {
        this.in_wanted = in_wanted;
    }

    @Override
    public String toString() {
        return "Movie [title=" + title + ", in_wanted=" + in_wanted + "]";
    }
}

class Profile {

    private boolean value;

    public boolean isValue() {
        return value;
    }

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

    @Override
    public String toString() {
        return String.valueOf(value);
    }
}

现在，当我们拥有所有需要的类时，我们应该实现新的自定义反序列化器：

class ProfileJsonDeserializer implements JsonDeserializer<Profile> {
    @Override
    public Profile deserialize(JsonElement jsonElement, Type type,
            JsonDeserializationContext context) throws JsonParseException {
        if (jsonElement.isJsonPrimitive()) {
            return null;
        }

        return context.deserialize(jsonElement, JsonProfile.class);
    }
}

class JsonProfile extends Profile {

}

请查看JsonProfile课程。我们必须创建它以避免“反序列化循环”（棘手的部分）。

现在我们可以用测试方法测试我们的解决方案：

GsonBuilder builder = new GsonBuilder();
builder.registerTypeAdapter(Profile.class, new ProfileJsonDeserializer());
Gson gson = builder.create();

JsonEntity jsonEntity = gson.fromJson(new FileReader("/tmp/json.txt"),
        JsonEntity.class);
System.out.println(jsonEntity);

Answer 2

您可以进行手动解析，例如：

JsonParser parser = new JsonParser();
JsonObject rootObject = parser.parse(yourJsonString).getAsJsonObject();
JsonObject movieObject = rootObject
                           .getAsJsonArray("movies")
                           .get(0).getAsJsonObject();
JsonElement inWantedElement = movieObject.get("in_wanted");

//Check if "in_wanted" element is a boolean or an object
if (inWantedElement.isJsonObject()) {
    //Process the element as an object...
    //for example get the element "value"...
    boolean value = inWantedElement
                      .getAsJsonObject()
                      .getAsJsonObject("profile")
                      .getAsJsonPrimitive("value")
                      .getAsBoolean();
}
else if (inWantedElement.isJsonPrimitive()) {
    //Process the element as a boolean...
    boolean inWanted = inWantedElement.getAsBoolean();
}

注意：有关类型JsonObject，JsonArray，JsonElement等的详细信息，请参阅Gson API documentation ...

Gson用不同的值类型反序列化json

2 个答案: