Gson Generics屬性

Question

我對GSON庫有疑問

這是我的一個類的源代碼

public class Response<T>
{
    public int count;
    public ArrayList<T> items;


    public Response()
    {

    }
}


public class AudioDto
{
    public long id;

    public long owner_id;

    public String artist;

    public String title;

    public long duration;

    public String url;

    public long lyrics_id;

    public long album_id;

    public long genre_id;

    @Override
    public String toString()
    {
        return "AudioDto [id=" + id + ", owner_id=" + owner_id + ", artist=" + artist + ", title=" + title + ", duration=" + duration + ", url=" + url + ", lyrics_id=" + lyrics_id + ", album_id=" + album_id + ", genre_id=" + genre_id + "]";
    }



}

和這里

        Gson gson = new Gson();

        Response<AudioDto> response = new Response<AudioDto>();
        response = gson.fromJson(responseElement, response.getClass());

問題是：

如何使GSON將JSON字符串反序列化為Response對象，並將所有項反序列化為AudioDto對象。 如果我手動指定ArrayList<AudioDto> ， ArrayList<AudioDto>考慮到“項目”字段中的項目是ArrayList<AudioDto>類型的對象，但參數化類型似乎將其強制轉換為Object類。

這是JSON字符串

{"count":166,"items":[{"id":231270625,"owner_id":205245503,"artist":"John Newman","title":"Love Me Again","duration":235,"url":"http://cs9-2v4.vk.me/p20/1ee1a056da24cb.mp3","lyrics_id":111547947,"genre_id":17},{"id":230612631,"owner_id":205245503,"artist":"Florence and The Machine","title":"No Light, No Light","duration":274,"url":"http://cs9-5v4.vk.me/p19/51a5b460796306.mp3","lyrics_id":20459437,"genre_id":18},{"id":230612324,"owner_id":205245503,"artist":"Backstreet Boys","title":"Incomplete","duration":239,"url":"http://cs9-4v4.vk.me/p13/b8dcc4cee8bf03.mp3","lyrics_id":268139,"genre_id":1}]}

Answer 1

首先，您不能使用ArrayList<T> items; 因為Gson嘗試將其轉換為LinkedList 。

因此，請使用List<T>代替。

之后，您可以嘗試：

GsonBuilder gsonB = new GsonBuilder();
Type collectionType = new TypeToken<Response<AudioDto>>() {}.getType();
//Response<AudioDto> response = new Response<AudioDto>();  // you don't need this row

Response<AudioDto> response = gsonB.create().fromJson(responseElement, collectionType);

//assert(response != null);

順便說一句，使用Gson gson = new Gson(); 而是GsonBuilder gsonB = new GsonBuilder(); 。

沒什么可配置的。

關於類型

據我所知，您不能創建<T> Type 。 但是您可以改用<AudioDto> Type ：

發射器類

....
LoadJson<AudioDto> lj = new LoadJson<AudioDto>();
Type collectionType = new TypeToken<Response<AudioDto>>() {}.getType();        
Response<AudioDto> response  = lj.load(responseElement, collectionType);  

LoadJson類

 public class LoadJson<T> {

 Response<T> load(String responseElement, Type classType){

  Gson gson = new Gson();

    Response<T> response = gson.fromJson(responseElement, classType);

  return response;
  }
}