Trying to parse JSON with GSON

Question

I'm trying to parse a JSON with GSON library on my Android App. I could parse correctly a JSON Array, but now I need to parse another json, with this estructure:

    {
    "articles": [
        {
            "article": {
                "articleId": 1,
                "articleName": "Bocadillo de calamares",
                "merchantId": 2,
                "price": 3.5
            },
            "computable": true,
            "orderArticleId": 3157,
            "orderId": 203,
            "price": 3.5,
            "requestedDate": "2012-11-19 13:15:20",
            "shared": true,
            "status": "AS01_INITIAL"
        },
        {
            "article": {
                "articleId": 3,
                "articleName": "Desayuno",
                "merchantId": 2,
                "price": 2.2
            },
            "computable": true,
            "orderArticleId": 3158,
            "orderId": 203,
            "price": 0,
            "requestedDate": "2012-11-19 13:17:30",
            "shared": true,
            "status": "AS01_INITIAL"
        },
        {
            "article": {
                "articleId": 2,
                "articleName": "Café",
                "merchantId": 2,
                "price": 1.1
            },
            "computable": true,
            "orderArticleId": 3156,
            "orderId": 203,
            "price": 1.1,
            "requestedDate": "2012-11-19 13:15:20",
            "shared": true,
            "status": "AS01_INITIAL"
        },
        {
            "article": {
                "articleId": 1,
                "articleName": "Bocadillo de calamares",
                "merchantId": 2,
                "price": 3.5
            },
            "computable": true,
            "orderArticleId": 3155,
            "orderId": 203,
            "price": 3.5,
            "requestedDate": "2012-11-19 12:40:17",
            "shared": true,
            "status": "AS01_INITIAL"
        }
    ],
    "comment": null,
    "creationDate": "2012-11-19 12:06:41",
    "customer": {
        "creationDate": 1353321506000,
        "customerId": 152,
        "devices": [
            {
                "customerId": 152,
                "deviceId": "2000",
                "phone": null
            }
        ],
        "image": false,
        "mail": null,
        "name": null,
        "password": null
    },
    "finishDate": null,
    "group": 0,
    "groupOrders": [],
    "location": {
        "location": "Table 1",
        "locationId": 1,
        "shopId": 2
    },
    "orderId": 203,
    "parentOrderId": 192,
    "score": null,
    "shopId": 2,
    "status": "OS01_INITIAL",
    "ticketUrl": null,
    "tip": null,
    "total": 0,
    "totalArticles": 0,
    "type": "BILL"
}


I have a Order.class like this:

    public class Order {

    private final String orderId;
    (....)
    private final ArrayList<Articles> articles;
    private final String group;


    public Order() {

        orderId = "";
         (....)

        articles = new ArrayList<Articles>();
        group = "";
    }

    public String getOrderId() {
        return orderId;
    }

     (... All getters for each element)

    public ArrayList<Articles> getArticles() {
        return articles;
    }
}

And a Articles.class

public class Articles {

private final String orderArticleId;
(...)
private final ArrayList<Article> article;

public Articles() {
    orderArticleId = "";
    (....)
    article = new ArrayList<Article>();

};

public String getPrice() {
    return price;
}

(....All getters for each element)

public ArrayList<Article> getArticle() {
    return article;
}

}

And, on my main activity I try to get all the info whith this:

    final Gson gson = new Gson();
    Order o = gson.fromJson(jsonData, Order.class);
    System.out.println(" - " +  o.getOrderId() );

And works ok, but if I want to get Articles info, the values are null, and I don't know how can I get it.

I try with something like that:

 Type collectionType = new TypeToken<List<Merchants>>() {
            }.getType();
            data = gson.fromJson(response, collectionType);

And I try to use a ArticlesWrapper, but I don't know how to do it exactly. But I think I forgetting something... and I don't know what. In another part of the app, I deserialize correctly a JSON because it is an Array, but on this case I don't know how can I get all the data correctly.

If you need more information, I will provide you!. Thanks!

Answer 1

This is because you are not translating correctly the JSON structure to Java POJOs, basically omitting some fields you have the following structure.

+ Order
    + List<BigArticle> articles
    + Customer customer
    + Location location
    + other basic fields

+ BigArticle
    + Article article
    + other basic fields

+ Article
    + basic fields

+ Customer
    + List<Device> devices
    + other basic fields

+ Device
    + basic fields

+ Location
    + basic fields

So you should end up with 6 Java POJOs that GSon should be able to populate while deserializing the JSON data.

I just translated your JSON structure to POJO here, and I've let Dates as String to simplify the parsing. If you want to have java.util.Date populated correctly you will have to customize the GSon instance.

Main class

public class Main {
    public static void main(String[] args) {
        String jsonData = "...";
        final Gson gson = new Gson();
        Order o = gson.fromJson(jsonData, Order.class);
        System.out.println("orderId: " +  o.getOrderId());
        System.out.println("first article price: " + o.getArticles().get(0).getPrice());
        System.out.println("second article status: " + o.getArticles().get(1).getStatus());
        System.out.println("third article requested date: " + o.getArticles().get(2).getRequestedDate());
    }
}

Order

public class Order {
    private List<BigArticle> articles;
    private String comment;
    private String creationDate;
    private Customer customer;
    private String finishDate;
    private int group;
    private List<Integer> groupOrders;
    private Location location;
    private int orderId;
    private int parentOrderId;
    private int score;
    private int shopId;
    private String status;
    private String ticketUrl;
    private String tip;
    private int total;
    private int totalArticles;
    private String type;

    // getters and setters
}

BigArticle

public class BigArticle {
    private Article article;
    private boolean computable;
    private int orderArticleId;
    private int orderId;
    private double price;
    private String requestedDate;
    private boolean shared;
    private String status;

    // getters and setters
}

Article

public class Article {
    private int articleId;
    private String articleName;
    private int merchantId;
    private double price;

    // getters and setters
}

Customer

public class Customer {
    private long creationDate;
    private int customerId;
    private List<Device> devices;
    private boolean image;
    private String mail;
    private String name;
    private String password;

    // getters and setters
}

Device

public class Device {
    private int customerId;
    private String deviceId;
    private String phone;

    // getters and setters
}

Location

public class Location {
    private String location;
    private int locationId;
    private int shopId;

    // getters and setters
}

Output

orderId: 203
first article price: 3.5
second article status: AS01_INITIAL
third article requested date: 2012-11-19 13:15:20