Parsing object with dynamic key through gson

Question

Like the title says, I am trying to parse an object which key is a dynamic String. I've looked quite a while for some answers and found 1. this, 2.this and 3. this

For your information, I kinda new to Java and this is my first time working with Json data and parsing

The Json response looks like this:

{"Narcos": {"episodes": [{"season": 2, "name": "Episode #2.1", "number": 1}, {"season": 2, "name": "Episode #2.10", "number": 10}, {"season": 2, "name": "Episode #2.2", "number": 2}, {"season": 2, "name": "Episode #2.3", "number": 3}, {"season": 2, "name": "Episode #2.4", "number": 4}, {"season": 2, "name": "Episode #2.5", "number": 5}, {"season": 2, "name": "Episode #2.6", "number": 6}, {"season": 2, "name": "Episode #2.7", "number": 7}, {"season": 2, "name": "Episode #2.8", "number": 8}, {"season": 2, "name": "Episode #2.9", "number": 9}, {"season": 1, "name": "Descenso", "number": 1}, {"season": 1, "name": "Despegue", "number": 10}, {"season": 1, "name": "Explosivos", "number": 6}, {"season": 1, "name": "La Catedral", "number": 9}, {"season": 1, "name": "La Gran Mentira", "number": 8}, {"season": 1, "name": "The Men of Always", "number": 3}, {"season": 1, "name": "The Palace in Flames", "number": 4}, {"season": 1, "name": "The Sword of Sim\u00f3n Bolivar", "number": 2}, {"season": 1, "name": "There Will Be a Future", "number": 5}, {"season": 1, "name": "You Will Cry Tears of Blood", "number": 7}], "year": 2015}}

The dynamic key, is in this example "Narcos". Its basically the name of the show you want the episodes for.

I tried different approaches. For the first link, the code for parsing looks like this:

ApiTest.class

Type mapType = new  TypeToken<Map<String, Serie> >() {}.getType(); // define generic type

    Map<String, Serie> serie = gson.fromJson(jsonString, mapType);

Serie.class

 public class Serie {

    private Episodes episodes;

Episodes.class

public class Episodes {

    private Episode[] episode;
    private int year;

Episode.class

public class Episode {

    private int season;
    private String name;
    private int number;

When I go with the first approach, I get this error

Exception in thread "main" com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 41 path $..episodes
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:224)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:129)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:220)
    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:41)
    at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:187)
    at com.google.gson.internal.bind.MapTypeAdapterFactory$Adapter.read(MapTypeAdapterFactory.java:145)
    at com.google.gson.Gson.fromJson(Gson.java:887)
    at com.google.gson.Gson.fromJson(Gson.java:852)
    at com.google.gson.Gson.fromJson(Gson.java:801)
    at testing.ApiTest.main(ApiTest.java:114)
Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 41 path $..episodes
    at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:385)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:213)
    ... 9 more

When I tried to parse the data according to the other two threads, I created a response class like this:

PoroResponse.class

public class PoroResponse {

    private Map<String, Serie> serie;

and changed the code in ApiTest.class to:

PoroResponse poro = gson.fromJson(jsonString, PoroResponse.class);

and tried to get an array to work with through this:

Episode[] episodes = poro.get(poro).getSerie().getEpisodes().getEpisode();

I also tried to parse it like this:

Object o = new Gson().fromJson(json, Object.class);

But in both of the last cases either my Serie object is NULL or I get a LinkedTreeMap with NULL values.

Could someone point me in the right direction? I've been stuck at this problem since 2 days and honestly have no real idea how to fix it.

Answer 1

Maybe you can try this: Episode class

    public class Episode {

    @SerializedName("season")
    @Expose
    private Integer season;
    @SerializedName("name")
    @Expose
    private String name;
    @SerializedName("number")
    @Expose
    private Integer number;


    public Integer getSeason() {
        return season;
    }


    public void setSeason(Integer season) {
        this.season = season;
    }


    public String getName() {
        return name;
    }


    public void setName(String name) {
        this.name = name;
    }


    public Integer getNumber() {
        return number;
    }


    public void setNumber(Integer number) {
        this.number = number;
    }

 }

Then Serial class:

    public class Serial {

    @SerializedName("episodes")
    @Expose
    private List<Episode> episodes = new ArrayList<Episode>();
    @SerializedName("year")
    @Expose
    private Integer year;

    public List<Episode> getEpisodes() {
        return episodes;
    }


    public void setEpisodes(List<Episode> episodes) {
        this.episodes = episodes;
    }


    public Integer getYear() {
        return year;
    }


    public void setYear(Integer year) {
        this.year = year;
    }

 }

Then to generate JAVA objects with dynamic keys from JSON just run this:

Type type = new TypeToken<Map<String, Serial>>() {
        }.getType();
Map<String, Serial> result = new Gson()
                .fromJson(new InputStreamReader(new ByteArrayInputStream(jsonString.getBytes())), type);

To get for example Narcos serial information you need to write this:

Serial narcosSerial = result.get("Narcos");