GSON Collections Limitations

Question

This is a follow up to a previously asked question. How can I parse a JSON object that contains an array of items see the following link for the JSON response? The response is too large and I thought of putting it in a google drive here.

I am using http://www.jsonschema2pojo.org/ to create the POJOs. My code is as follows

public void onResponse(Call call, Response response) throws IOException {

    String mMessage = response.body().string();
    if (response.isSuccessful()) {
        try {
            Gson gson = new Gson();
            ProductsByCategory items = gson.fromJson(mMessage, ProductsByCategory.class);

            response.close();
        } catch (Exception e) {
            Log.e("Error", "Failed to upload");
            e.printStackTrace();
        }
    } else {
        errorMessage(mMessage);
    }
} 

When debugging items I find that all the items are null. Can this be achieved with GSON or will i have to use another library:

The ProductsByCategory Class is as follows:

public class ProductsByCategory{

    @SerializedName("id")
    @Expose
    private Integer id;
    @SerializedName("name")
    @Expose
    private String name;
    @SerializedName("slug")
    @Expose
    private String slug;
    @SerializedName("permalink")
    @Expose
    private String permalink;
    @SerializedName("date_created")
    @Expose
    private String dateCreated;
    @SerializedName("date_created_gmt")
    @Expose
    private String dateCreatedGmt;
    @SerializedName("date_modified")
    @Expose
    private String dateModified;
    @SerializedName("date_modified_gmt")
    @Expose
    private String dateModifiedGmt;
    @SerializedName("type")
    @Expose
    private String type;
    @SerializedName("status")
    @Expose
    private String status;
    @SerializedName("featured")
    @Expose
    private Boolean featured;
    @SerializedName("catalog_visibility")
    @Expose
    private String catalogVisibility;
    @SerializedName("description")
    @Expose
    private String description;
    @SerializedName("short_description")
    @Expose
    private String shortDescription;
    @SerializedName("sku")
    @Expose
    private String sku;
    @SerializedName("price")
    @Expose
    private String price;
    @SerializedName("regular_price")
    @Expose
    private String regularPrice;
    @SerializedName("sale_price")
    @Expose
    private String salePrice;
    @SerializedName("date_on_sale_from")
    @Expose
    private Object dateOnSaleFrom;
    @SerializedName("date_on_sale_from_gmt")
    @Expose
    private Object dateOnSaleFromGmt;
    @SerializedName("date_on_sale_to")
    @Expose
    private Object dateOnSaleTo;
    @SerializedName("date_on_sale_to_gmt")
    @Expose
    private Object dateOnSaleToGmt;
    @SerializedName("price_html")
    @Expose
    private String priceHtml;
    @SerializedName("on_sale")
    @Expose
    private Boolean onSale;
    @SerializedName("purchasable")
    @Expose
    private Boolean purchasable;
    @SerializedName("total_sales")
    @Expose
    private Integer totalSales;
    @SerializedName("virtual")
    @Expose
    private Boolean virtual;
    @SerializedName("downloadable")
    @Expose
    private Boolean downloadable;
    @SerializedName("downloads")
    @Expose
    private List<Object> downloads = null;
    @SerializedName("download_limit")
    @Expose
    private Integer downloadLimit;
    @SerializedName("download_expiry")
    @Expose
    private Integer downloadExpiry;
    @SerializedName("external_url")
    @Expose
    private String externalUrl;
    @SerializedName("button_text")
    @Expose
    private String buttonText;
    @SerializedName("tax_status")
    @Expose
    private String taxStatus;
    @SerializedName("tax_class")
    @Expose
    private String taxClass;
    @SerializedName("manage_stock")
    @Expose
    private Boolean manageStock;
    @SerializedName("stock_quantity")
    @Expose
    private Integer stockQuantity;
    @SerializedName("in_stock")
    @Expose
    private Boolean inStock;
    @SerializedName("backorders")
    @Expose
    private String backorders;
    @SerializedName("backorders_allowed")
    @Expose
    private Boolean backordersAllowed;
    @SerializedName("backordered")
    @Expose
    private Boolean backordered;
    @SerializedName("sold_individually")
    @Expose
    private Boolean soldIndividually;
    @SerializedName("weight")
    @Expose
    private String weight;
    @SerializedName("dimensions")
    @Expose
    private Dimensions dimensions;
    @SerializedName("shipping_required")
    @Expose
    private Boolean shippingRequired;
    @SerializedName("shipping_taxable")
    @Expose
    private Boolean shippingTaxable;
    @SerializedName("shipping_class")
    @Expose
    private String shippingClass;
    @SerializedName("shipping_class_id")
    @Expose
    private Integer shippingClassId;
    @SerializedName("reviews_allowed")
    @Expose
    private Boolean reviewsAllowed;
    @SerializedName("average_rating")
    @Expose
    private String averageRating;
    @SerializedName("rating_count")
    @Expose
    private Integer ratingCount;
    @SerializedName("related_ids")
    @Expose
    private List<Integer> relatedIds = null;
    @SerializedName("upsell_ids")
    @Expose
    private List<Object> upsellIds = null;
    @SerializedName("cross_sell_ids")
    @Expose
    private List<Object> crossSellIds = null;
    @SerializedName("parent_id")
    @Expose
    private Integer parentId;
    @SerializedName("purchase_note")
    @Expose
    private String purchaseNote;
    @SerializedName("categories")
    @Expose
    private List<Category> categories = null;
    @SerializedName("tags")
    @Expose
    private List<Object> tags = null;
    @SerializedName("images")
    @Expose
    private List<Image> images = null;
    @SerializedName("attributes")
    @Expose
    private List<Attribute> attributes = null;
    @SerializedName("default_attributes")
    @Expose
    private List<Object> defaultAttributes = null;
    @SerializedName("variations")
    @Expose
    private List<Integer> variations = null;
    @SerializedName("grouped_products")
    @Expose
    private List<Object> groupedProducts = null;
    @SerializedName("menu_order")
    @Expose
    private Integer menuOrder;
    @SerializedName("meta_data")
    @Expose
    private List<MetaDatum> metaData = null;
    @SerializedName("_links")
    @Expose
    private Links links;

    /**
     * No args constructor for use in serialization
     * 
     */
    public ProductsByCategory() {
    }
}

Answer 1

If you have used http://www.jsonschema2pojo.org/ to make your POJO files, then please check there is a class like the following.

public class Example {

    @SerializedName("ProductsByCategory")
    @Expose
    public ProductsByCategory[] productsByCategory;

}

You need to use that class while parsing JSON with Gson like this.

Example items = gson.fromJson(mMessage, Example.class);