CODEWITHSUNDEEP
javajsongson
FernandoPaiva
FernandoPaiva

Reputation: 4460

Converting JSONArray to List<Object>?

I'm trying deserializes a JSONArray to List. To do it I'm trying use Gson but I can't understand why doesn't works and all values of JSON are null.

How could I do this ?

JSON 

{ "result" : [ 
      { "Noticia" : { 
            "created" : "2015-08-20 19:58:49",
            "descricao" : "tttttt",
            "id" : "19",
            "image" : null,
            "titulo" : "ddddd",
            "usuario" : "FERNANDO PAIVA"
          } },
      { "Noticia" : { 
            "created" : "2015-08-20 19:59:57",
            "descricao" : "hhhhhhhh",
            "id" : "20",
            "image" : "logo.png",
            "titulo" : "TITULO DA NOTICIA",
            "usuario" : "FERNANDO PAIVA"
          } }
    ] }

Deserializes 

List<Noticia> lista = new ArrayList<Noticia>();
                            Gson gson = new Gson();
                            JSONArray array = obj.getJSONArray("result");

                            Type listType = new TypeToken<List<Noticia>>() {}.getType();
                            lista = gson.fromJson(array.toString(), listType);

                            //testing - size = 2 but value Titulo is null
                            Log.i("LISTSIZE->", lista.size() +"");
                            for(Noticia n:lista){
                                Log.i("TITULO", n.getTitulo());
                            }

Class Noticia

public class Noticia implements Serializable {
    private static final long serialVersionUID = 1L;

    private Integer id;
    private String titulo;
    private String descricao;
    private String usuario;
    private Date created;
    private String image;

Upvotes: 14

Views: 43242

Answers (5)

M Hamza Tahir
M Hamza Tahir

Reputation: 11

Kotlin Ex :
we getting response in form of JSONArry

call.enqueue(object : Callback<JsonArray> {
        override fun onResponse(call: Call<JsonArray>, response: Response<JsonArray>) {

            val list = response.body().toString()
            val gson = Gson()
            val obj: CitiesList? = gson.fromJson(list, CitiesList::class.java)
            cityLiveData.value = obj!!
           

        }

        override fun onFailure(call: Call<JsonArray>, t: Throwable) {
          
        }

    })

Here CitiesList CitiesList::class.java is the ArrayList of Cities object

class CitiesList : ArrayList<CitiesListItem>()

Before using GSON add dependancey in Gradle

dependencies {

implementation 'com.google.code.gson:gson:2.8.8'

}

Upvotes: 0

cнŝdk
cнŝdk

Reputation: 32145

There are two problems with your code :

  1. First is that you are using a getJsonArray() to get the array, which isn't part of Gson library, you need to use getAsJsonArray() method instead.
  2. Second is that you are using array.toString() which isn't obvious because for the fromJson method you need a jsonArray as parameter and not String and that will cause you parse problems, just remove it.

And use the following code to convert your jsonArray to List<Noticia> :

Type type = new TypeToken<List<Noticia>>() {}.getType();
List<Noticia> lista = gson.fromJson(array, type);

And your whole code will be:

Gson gson = new Gson();
JSONArray array = obj.getAsJsonArray("result");

Type type = new TypeToken<List<Noticia>>() {}.getType();
List<Noticia> lista = gson.fromJson(array, type);

//testing - size = 2 but value Titulo is null
Log.i("LISTSIZE->", lista.size() +"");
for(Noticia n:lista){
   Log.i("TITULO", n.getTitulo());
}

Upvotes: 4

Saurabh
Saurabh

Reputation: 2472

Noticia.java

public class Noticia {
    private String created;
    private String descricao;
    private String id;
    private String image;
    private String titulo;
    private String usuario;
    public String getCreated() {
        return created;
    }
    public void setCreated(String created) {
        this.created = created;
    }
    public String getDescricao() {
        return descricao;
    }
    public void setDescricao(String descricao) {
        this.descricao = descricao;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getImage() {
        return image;
    }
    public void setImage(String image) {
        this.image = image;
    }
    public String getTitulo() {
        return titulo;
    }
    public void setTitulo(String titulo) {
        this.titulo = titulo;
    }
    public String getUsuario() {
        return usuario;
    }
    public void setUsuario(String usuario) {
        this.usuario = usuario;
    }
    @Override
    public String toString() {
        return "Noticia [created=" + created + ", descricao=" + descricao
                + ", id=" + id + ", image=" + image + ", titulo=" + titulo
                + ", usuario=" + usuario + "]";
    }
}

Result.java

public class Result {
    private Noticia Noticia;

    public Noticia getNoticia() {
        return Noticia;
    }

    public void setNoticia(Noticia noticia) {
        Noticia = noticia;
    }

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

}

Item.java

import java.util.List;

public class Item {
    private List<Result> result;

    public List<Result> getResult() {
        return result;
    }

    public void setResult(List<Result> result) {
        this.result = result;
    }

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

Main.java

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.testgson.beans.Item;

public class Main {
    private static Gson gson;

    static {
        gson = new GsonBuilder().create();
    }

    public static void main(String[] args) {
        String j = "{\"result\":[{\"Noticia\":{\"created\":\"2015-08-20 19:58:49\",\"descricao\":\"tttttt\",\"id\":\"19\",\"image\":null,\"titulo\":\"ddddd\",\"usuario\":\"FERNANDO PAIVA\"}},{\"Noticia\":{\"created\":\"2015-08-20 19:59:57\",\"descricao\":\"hhhhhhhh\",\"id\":\"20\",\"image\":\"logo.png\",\"titulo\":\"TITULO DA NOTICIA\",\"usuario\":\"FERNANDO PAIVA\"}}]}";
        Item r = gson.fromJson(j, Item.class);
        System.out.println(r);
    }
}

Final result

Item [result=[Result [Noticia=Noticia [created=2015-08-20 19:58:49, descricao=tttttt, id=19, image=null, titulo=ddddd, usuario=FERNANDO PAIVA]], Result [Noticia=Noticia [created=2015-08-20 19:59:57, descricao=hhhhhhhh, id=20, image=logo.png, titulo=TITULO DA NOTICIA, usuario=FERNANDO PAIVA]]]]

Upvotes: 1

Atul
Atul

Reputation: 2711

I think the problem could be something to do with toString() on JSONArray. But are you using obj.getAsJsonArray method?

Try this:

JSONArray arr = obj.getAsJsonArray("result"); 

            Type listType = new TypeToken<List<Noticia>>() {
            }.getType();
            return new Gson().fromJson(arr , listType);

Upvotes: 1

ziviland
ziviland

Reputation: 134

You parse json, that looks like 

{ "result" : [ 
  { 
        "created" : "2015-08-20 19:58:49",
        "descricao" : "tttttt",
        "id" : "19",
        "image" : null,
        "titulo" : "ddddd",
        "usuario" : "FERNANDO PAIVA"
   },
  { 
        "created" : "2015-08-20 19:59:57",
        "descricao" : "hhhhhhhh",
        "id" : "20",
        "image" : "logo.png",
        "titulo" : "TITULO DA NOTICIA",
        "usuario" : "FERNANDO PAIVA"
      }
] }

You need to make another object Item and parse a list of them.

public class Item{
    Noticia noticia; 
}

Or you can interate through JSONArray, get field "noticia" from each then parse Noticia object from given JSONObject.

Upvotes: 0

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