无法创建JsonObject java.lang.IllegalStateException：不是JSON对象

Question

I have this code where "Ocupacion" is object class that have another atribute objects. (since is a large class i don't post all the atributes of the class)

public String genHor(){
    Collection<Ocupacion> ocupas = new ArrayList<>();
    ocupas= H.makeOcupacion();
    Gson gson = new Gson();
    return gson.toJson(ocupas);
}

Then in another class where i recive the json String and i want to parse it. I do that:

public void assig(String json){
    JsonObject obj = new JsonParser().parse(json).getAsJsonObject();
}

Then i get the java.lang.IllegalStateException: Not a JSON Object

String json is like that:

[{"sesionConcreta":{"grup":{"NumGr":10,"TamGr":200,"subgrupo":[{"NumSub":11,"TamSub":200}],"asignatura":"prop"},"sessio":{"HorasSes":2,"TipoSes":"TEORIA"}},"aula":{"NomAu":"a5105","Capacidad":200,"Tipo":"lab"},"diayHora":{"Dia":"L","Hora":8}}]

Answer 1

[{"sesionConcreta":{"grup":{"NumGr":10,"TamGr":200,"subgrupo":[{"NumSub":11,"TamSub":200}],"asignatura":"prop"},"sessio":{"HorasSes":2,"TipoSes":"TEORIA"}},"aula":{"NomAu":"a5105","Capacidad":200,"Tipo":"lab"},"diayHora":{"Dia":"L","Hora":8}}]

it is a json array not a json object because it is in [] not in {} :

JsonArray jsonArr = new JsonParser().parse(json).getAsJsonArray();

JsonObject obj = jsonArr.get(0).getAsJsonObject();

JsonObject sesionConcretaObj = obj.get("sesionConcreta").getAsJsonObject();

JsonObject groupObj = sesionConcretaObj.get("grup").getAsJsonObject();

int numGr = groupObj.get("NumGr").getAsInt();

Answer 2

The jsonString is actually a jsonArray not a jsonObject. Try with below:

String jsonStr = "[{\"sesionConcreta\":{\"grup\":{\"NumGr\":10,\"TamGr\":200,\"subgrupo\":[{\"NumSub\":11,\"TamSub\":200}],\"asignatura\":\"prop\"},\"sessio\":{\"HorasSes\":2,\"TipoSes\":\"TEORIA\"}},\"aula\":{\"NomAu\":\"a5105\",\"Capacidad\":200,\"Tipo\":\"lab\"},\"diayHora\":{\"Dia\":\"L\",\"Hora\":8}}]";

JSONArray jsonarray = new JSONArray(jsonStr);

for(int i = 0; i< jsonarray.length(); i++) {
  JSONObject sesionConcreta = (JSONObject)jsonarray.getJSONObject(i).get("sesionConcreta");
  JSONObject grup = (JSONObject)sesionConcreta.get("grup");
  System.out.println(grup.get("NumGr"));
}

Answer 3

try this one:

public static void assig(String json){
        Gson gson = new Gson();
        Ocupacion[] occs = gson.fromJson(json, Ocupacion[].class); 
        System.out.println(occs);
}