Json to objects in Java (Gson)

Question

I'm trying to create objects with this JSON:

{
"data": {
  "Prueba1": {
     "id": 266,
     "title": "Prueba1",
     "name": "Prueba1",
     "key": "Prueba1",
     "lore": "Prueba1"
  },
  "Prueba2": {
     "id": 111,
     "title": "Prueba2",
     "name": "Prueba2",
     "key": "Prueba2",
     "lore": "Prueba2"
  }
 },
"type": "prueba",
"version": "1.0"
}

The problem is that Gson is giving me the object 'data' but I can't not conver it to an array of objects.

My actual code is:

    JsonParser parser = new JsonParser();
    FileReader fr = new FileReader("route to archive json");
    JsonElement datos = parser.parse(fr);
    JsonElement heroes = datos.getAsJsonObject().get("data");

   final Gson gson = new Gson();
    final Type tipoListaEmpleados = new TypeToken<List<hero>>(){}.getType();
    final List<hero> hero = gson.fromJson(heroes, tipoListaEmpleados);

    System.out.println(hero.get(2));

But it's throwing error:

Expected BEGIN_ARRAY but was BEGIN_OBJECT at path $

Any tip about the problem would be appreciated.

P.S: I understand that is giving all object, but I don't get the point of why is this happening, please help!!

EDIT: I'm working with an external API, that gives me that result, so I can't change the rest response, I need to convert to objects without adding []

EDIT2: Hero class looks like a single POJO :

public class hero
{
public int id;
public String title;
public String name;
public String key;
public String lore;
//constructor getters and setters
}

Why don't you have [ and ] if it's mention to be array of objects? It looks like a map to me. — Peter Lawrey
– Peter Lawrey, Commented Oct 17, 2016 at 13:56
The outer element in your sample JSON is an object with {}. But you are trying to deserialize a List<hero> which would expect the outer element to be an array with []. This is why you're getting that error message. — nickb
– nickb, Commented Oct 17, 2016 at 13:59
The issue may be that you're trying to parse a single JSON object into a List<hero>. You haven't shown us what Hero looks like but there's no array to convert into a List in your JSON. — Zircon
– Zircon, Commented Oct 17, 2016 at 13:59
Having Prueba1 and Prueba2 let me thing those two should be in an array without the Prueba name for each element. Hving something like {"data":[{"id":266,...},{"id":111}]} — AxelH
– AxelH, Commented Oct 17, 2016 at 14:08

jseashell · Accepted Answer · 2016-10-17 14:03:51Z

1

Your JSON doesn't actually have a JSON Array in it. Try this...although this might not be the exact structure you're looking for.

{
    "data": [{
        "Prueba1": {
            "id": 266,
            "title": "Prueba1",
            "name": "Prueba1",
            "key": "Prueba1",
            "lore": "Prueba1"
        },
        "Prueba2": {
            "id": 111,
            "title": "Prueba2",
            "name": "Prueba2",
            "key": "Prueba2",
            "lore": "Prueba2"
        }
    }],
    "type": "prueba",
    "version": "1.0"
}

You can use http://www.jsoneditoronline.org/ to verify your JSON and tweak accordingly

answered Oct 17, 2016 at 14:03

jseashell

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7 Comments

Jota Ge Over a year ago

I tried with this JSON, but still not working with the code I posted in the question =D

jseashell Over a year ago

@JotaGe you'll probably have to use this line too instead JsonElement heroes = datos.getAsJsonArray().get("data");

Jota Ge Over a year ago

Yes, I have that line

jseashell Over a year ago

No, you're getting it as an object and using JsonElement heroes = datos.getAsJsonObject().get("data");

jseashell Over a year ago

Also, where is elemento in final List<hero> hero = gson.fromJson(elemento, tipoListaEmpleados); coming from?

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