Using GSON to deserialize nested array

Question

Giving

JSON

// imagine this is JSON of a city
{
    "title" : "Troy"
    "people" : [
        {
            {
                "title" : "Hector",
                "status" : "Dead"
            },
            {
                "title" : "Paris",
                "status" : "Run Away"
            }
        },
        ...
    ],
    "location" : "Mediteranian",
    "era" : "Ancient",
    ...
}

City

public class City {
    @SerializeName("title")
    String title;
    @SerializeName("people")
    List<Person> people;
    @SerializeName("location")
    String location;
    @SerializeName("era")
    String era;
    ...
}

Person

public class Person {
    @SerializeName("title")
    private String title;
    @SerializeName("status")
    private String status;
}

If having string of JSON above, it is possible to create list of person

A. without having to deserialize City first like following

City city = new Gson().fromJson(json, City.class)
ArrayList<Person> people = city.people;

And

B. without having to convert string to JSONObject, get JSONArray and then convert back to string like following

String peopleJsonString = json.optJSONArray("people").toString
ArrayList<Person> people = new Gson().fromJSON(peopleJsonString, Person.class);

kevinpelgrims · Accepted Answer · 2016-03-07 16:38:56Z

4

You can use a custom JsonDeserializer, which is part of Gson (com.google.gson.JsonDeserializer).

Simple example:

public class WhateverDeserializer implements JsonDeserializer<Whatever> {
  @Override
  public Whatever deserialize(final JsonElement json, final Type typeOfT, final JsonDeserializationContext context) throws JsonParseException {
    Whatever whatever = new Whatever();
    // Fetch the needed object here
    // whatever.setNeededObject(neededObject);
    return whatever;
  }
}

You can then apply this deserializer like this:

Gson gson = new GsonBuilder()
            .registerTypeAdapter(Whatever.class, new WhateverDeserializer())
            .create();

There is a full example of how to use a custom deserializer, including a super detailed explanation, on this page: http://www.javacreed.com/gson-deserialiser-example/

answered Mar 7, 2016 at 16:38

kevinpelgrims

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Comments

UMESH0492 · Accepted Answer · 2016-03-07 16:16:21Z

0

I don't think you can get the list directly without parsing the json array. You need to parse the array. And it would be faster via Gson;

If you strictly need (only array) and you won't be using any other json object . Simply delete them, so that gson won't parse them.

edited Mar 7, 2016 at 16:16

answered Mar 7, 2016 at 15:53

UMESH0492

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1 Comment

Sevle Over a year ago

Take a closer look to the question and the limitations that @Tar_Tw45 set.

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