Insert a nested JSON array into SQLite after parsing with Gson

Question

After parsing a nested JSON array with Gson , I now need to insert the result into SQLite . I tried inserting as done when not parsing with Gson , but that didn't work. I looked for ways to do that but couldn't find a solution.

The JSON parsing:

Gson gson = new Gson();
Type listType = new TypeToken<List<Country>>(){}.getType();
List<Country> countriesList = gson.fromJson(jsonString, listType);
for(Country country : countriesList) {
    ContentValues insertValues;
}

If I wasn't using Gson, I would have written the line:

JSONObject countryObject = countriesList.getJSONObject(country);

EDIT

One of the objects from the JSON

[ 
   { 
      "name":"Afghanistan",
      "topLevelDomain":[ 
         ".af"
      ],
      "callingCodes":[ 
         "93"
      ],
      "capital":"Kabul",
      "region":"Asia",
      "subregion":"Southern Asia",
      "population":27657145,
      "latlng":[ 
         33.0,
         65.0
      ],
      "demonym":"Afghan",
      "area":652230.0,
      "gini":27.8,
      "timezones":[ 
         "UTC+04:30"
      ],
      "nativeName":"افغانستان",
      "numericCode":"004",
      "currencies":[ 
         { 
            "name":"Afghan afghani",
            "symbol":"؋"
         }
      ],
      "languages":[ 
         { 
            "name":"Pashto",
            "nativeName":"پښتو"
         },
         { 
            "name":"Uzbek",
            "nativeName":"Oʻzbek"
         },
         { 
            "name":"Turkmen",
            "nativeName":"Türkmen"
         }
      ],
      "translations":{ 
         "de":"Afghanistan",
      },
      "flag":"https://restcountries.eu/data/afg.svg",
      "cioc":"AFG"
   },

The model classes I wrote are only for the variables objects and arrays I needed.

The model class Country.Java

public class Country implements Parcelable {

    private String name;
    private String capital;
    private String region;
    private String subregion;
    private int population;
    private List<Double> latlng = new ArrayList<Double>();
    private double area;
    private double gini;
    private List<String> timezones = new ArrayList<String>();
    private List<Currency> currencies = new ArrayList<Currency>();
    private List<Language> languages = new ArrayList<Language>();
    private String flag;

    public Country() {}

//getters, setters, toString() and Parcelable methods
}

The model class Currency.Java

public class Currency implements Parcelable {

    private String name;
    private String symbol;

//getters, setters, toString() and Parcelable methods
}

The model class Language.Java

public class Language implements Parcelable {

    private String name;
    private String nativeName;

//getters, setters, toString() and Parcelable methods
}

Answer 1

It's hard to know where your problem is without more code. You are doing two different operations:

1. unmarshalling a json
2. persisting data in SQLite.

Unmarshalling json with Gson

Inside the for-loop, can you log each country to see that you are getting a valid object with all the fields set? It is very much possible that you need to create a factory yourself. Does Country have subtype that you need to register through RuntimeTypeAdapterFactory? Maybe something like

final RuntimeTypeAdapterFactory<City> typeFactory = RuntimeTypeAdapterFactory
  of(City.class, "MyCity")
  .registerSubtype(S...,...)

Save in SQLite

Once you have valid data, then you must convert per field like so

public static ContentValues getContentValues(Country country) {
    ContentValues values = new ContentValues();
    values.put(COLUMN_ID, country.getId());
    values.put(COLUMN_NAME, country.getName());
    ...
    return values;
}

And then, if it still doesn't work, you will need to look at your SQLite schema.

Answer 2

First get property of Country and then put it to content values and insert.

List<Country> countries = gson.fromJson(jsonString, new TypeToken<List<Country>>(){}.getType());

for(Country country : countries) {  

    String name = country.getName();
    String capital = country.getCapital();
    String region = country.getRegion();
    String currencies = gson.toJson(country.getCurrencies());
    ...

    ContentValues insertValues = new ContentValues();  
    insertValues.put("name", name)
    insertValues.put("capital", capital);
    insertValues.put("region", region); 
    insertValues.put("currencies", currencies); 
    ...

    long res = db.insert(TABLE_NAME, null, insertValues); 

}