Develop Reference

Retrofit,RxJava and Sqlite

I have retrieve data from Server using Retrofit and now I am trying to store with sqlite database
WebserviceHandler.getImagePathSelectAl()
.subscribeOn(Schedulers.io())
.flatMap(s -> WebserviceHandler.getCtbLeidSource())
.subscribeOn(Schedulers.io())
.subscribe(.................);
and response model class like
public class ImagePathResponse {
#SerializedName("Message")
#Expose
private String message;
#SerializedName("HasColumns")
#Expose
private Integer hasColumns;
#SerializedName("ErrorMessage")
#Expose
private String errorMessage;
#SerializedName("ImagePath_insert")
#Expose
private List<ImagePath> imagePathInsert = null;
#SerializedName("ImagePath_update")
#Expose
private List<ImagePath> imagePathUpdate = null;
and
public class LeedSourceResponse {
#SerializedName("Message")
#Expose
private String message;
#SerializedName("HasColumns")
#Expose
private Integer hasColumns;
#SerializedName("ErrorMessage")
#Expose
private String errorMessage;
#SerializedName("LeedSource_insert")
#Expose
private List<LeedSource> leedSourceInsert = null;
#SerializedName("LeedSource_update")
#Expose
private List<LeedSource> leedSourceUpdate = null;
now i want to insert and update sqlite db in each response, how can achieve this. I am new to RxJava and RxAndroid

You can check Rooms persistence library its a sql library for androidRooms , but in this case I would recommend you using RealmDb instead of sql, its much faster and would work perfectly if you want to save your date for every response.

Exclude some fields from JSON Body in POST request using Retrofit Android

I am using Retrofit2 to send and receive requests to my server.
Here are my API interface and Model class.
Interface
public interface ApiInterface {
#POST("/users/")
Call<User> signUp(#Body User user);
#POST("/login_url/")
Call<User> login(#Body User user);
}
Retrofit client
public class RetrofitClient {
private static Retrofit retrofit = null;
public static Retrofit getRestClient(String baseUrl) {
if (retrofit == null) {
retrofit = new Retrofit.Builder().baseUrl(baseUrl)
.addConverterFactory(GsonConverterFactory.create())
.build();
}
return retrofit;
}
}
POJO class
public class User {
#SerializedName("id")
private Integer id;
#SerializedName("email")
#Expose
private String email;
#SerializedName("first_name")
private String firstName;
#SerializedName("last_name")
private String lastName;
#SerializedName("password")
#Expose
private String password;
}
I have exposed email and password so that in login request these 2 parameters will be added.
But for another request like Sign up, I required a first name and last name also to be sent along with email and password.
Can I use same "User" class for both ? because if I expose the first name and last name then, those fields will be also sent in login request.
Is there any other way or should I make different POJO classes for both request ?

Instead of sending the whole class , you can use #Field annotation , so your login callback will be something like this :
#FormUrlEncoded
#POST("/login_url/")
Call<User> login(#field("email")String email,#field("password")String password);
#FormUrlEncoded denotes that the request body will use form URL encoding. Fields should be declared as parameters and annotated with #Field.

Can I use same "User" class for both ?
Yes , you can use the same Model as #Body for both requests !
Just make sure where you don't need the required variables just omit them !!
Remove the #SerializedName and #Expose , these are not required and give the variable names according to the json KEYs
public class User {
private Integer id;
private String email;
private String firstName;
private String lastName;
private String password;
}
Edit
Suppose for example , for one request you need :-
4 params you set the model user as
new User(id,email,firstname,lastname); // dont init the password attribute
5 params you set all values to the model like
new User(id,email,firstname,lastname,password);

Android Retrofit and GSON: JSON response returns object or string as property value

The JSON data returned from the server can either return an object, or if that object is null, it returns an empty string ("").
My problem is that my DTO expects an object, but it sees a string and crashes.
PersonDTO
data class PersonDto(
#SerializedName("firstName") val first: String,
#SerializedName("lastName") val last: String,
#SerializedName("favorites") val favorites: FavoriteDto,
)
FavoriteDto
class FavoriteDto(
#SerializedName("color") val color: String,
#SerializedName("number") val number: Int
)
Different responses from server
"person" : {
"firstName": "Steve",
"lastName" : "Johnson",
"favorites" : {
"color": "Purple",
"number": 25
}
}
...
"person" : {
"firstName": "Steve",
"lastName" : "Johnson",
"favorites" : ""
}
I've heard that I might need a custom GSON deserializer, but I've never done anything with GSON other than the out of the box stuff - so I was hoping for a nudge in the right direction.
Thanks!

Easiest hack is that you can add extra fields in the class with the same serialised name but with a String data type. Like this -
data class PersonDto(
#SerializedName("firstName") val first: String,
#SerializedName("lastName") val last: String,
#SerializedName("favorites") val favorites: FavoriteDto,
#SerializedName("favorites") val favoritesStr: String,
)
As there is nothing in Gson as "Required" field, you'll just get a null in your deserialized object if something is missing in the JSON. So, if there is an empty string the FavoriteDto object will be null and not null otherwise.
EDIT
I'm adding some Java code that I have written earlier. This might help:
public class PersonDto {
private FavoriteDto favorites;
private String favoritesStr;
public FavoriteDto getResponseDataObject() {
return favorites;
}
public void setResponseDataObject(FavoriteDto favorites) {
this.favorites = favorites;
}
public String getResponseDataString() {
return favoritesStr;
}
public void setResponseDataString(String favoritesStr) {
this.favoritesStr = favoritesStr;
}
Defining the Deserializar:
public static class ArrayObjectDualityDeserializer implements JsonDeserializer<PersonDto> {
public PersonDto deserialize(JsonElement json, Type typeOfT,
JsonDeserializationContext context) throws JsonParseException {
PersonDto response = new PersonDto();
JsonObject object = json.getAsJsonObject();
if(object.get("favorites").isJsonArray()) {
} else if(object.get("favorites").isJsonObject()) {
try {
FavoriteDto dtoObject = gson.fromJson(object.get("favorites"), FavoriteDto.class);
response.setResponseDataObject(dtoObject);
} catch (JsonSyntaxException e) {
DebugLogger.e("Error " + e);
}
} else if (object.get("favorites").isJsonNull()) {
} else {
response.setResponseDataString(object.get("favorites").getAsString());
}
}
}
And:
public static Gson gson = new GsonBuilder()
.registerTypeAdapter(PersonDto.class, new ArrayObjectDualityDeserializer())
.create();
Lastly:
private static Retrofit retrofit = null;
private static OkHttpClient.Builder httpClient = null;
private static OkHttpClient session_client = null;
httpClient = new OkHttpClient.Builder();
httpClient.addInterceptor(new SessionOkHttpInterceptor());
session_client = httpClient.build();
retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL)
.client(session_client)
.addConverterFactory(GsonConverterFactory.create(gson))
.build();

The answer of #Subrato M. is partially correct. In order to work, you should remove #SerializedName("favorites") annotation from both fields in order to work. In this case, Gson won't throw an error when deserialize multiple json fields named favorites because you don't have any field annotated with that name (also don't name fileds the same as expected field name beucase Gson will try to deserialize). Use the custom deserializer to check if is an object or a string.

Nowadays isn't necessary the #Subrato M's hack, you don't get the right json cause you are missing the data keyword before class FavoriteDto and that is why doesn't exists the get and set methods

Generic Type Gson deserializer

I have an Api which the api looks like this:
If the response is ok the structure will begin with data keyword for example:
{
"data": {
"name": "Rogelio Volkman",
"address": "27299 Will Bridge Suite 058\nWest Reubenhaven, MI 00736",
"lat": 54.65,
"lng": 111.75,
"phone": "+26(4)5015498663"
}
}
And if response is not Ok(status is not 200) response will not container data keyword so response will look like:
{
"message": "404 Not Found",
"status_code": 404
}
Since this structure is a common structure for all models I intended to create a Generic Deserializer for all models.
This looked like:
public class DataObjectDeserializer implements JsonDeserializer<Object> {
#Override
public Objectdeserialize(JsonElement je, Type type, JsonDeserializationContext jdc)
throws JsonParseException {
// Get the "data" element from the parsed JSON
JsonElement data = je.getAsJsonObject().get("data");
// Deserialize it. You use a new instance of Gson to avoid infinite recursion
// to this deserializer
return new Gson().fromJson(data, Object.class);
}
}
then registered it as typeAdapter Gson gson = new GsonBuilder().registerTypeHierarchyAdapter(Object.class, new DataObjectDeserializer()).create();
Since every object is an instance of Object I supposed this would work (deserialize my Museum model) but it didn't.
In my second attempt I created an abstract class called DataObjectModel and class Museum extended DataObjectModel. then created anoteher deserailizer like:
public class DataObjectDeserializer implements JsonDeserializer {
#Override
public DataObjectModel deserialize(JsonElement je, Type type, JsonDeserializationContext jdc)
throws JsonParseException {
// Get the "data" element from the parsed JSON
JsonElement data = je.getAsJsonObject().get("data");
// Deserialize it. You use a new instance of Gson to avoid infinite recursion
// to this deserializer
return new Gson().fromJson(data, DataObjectModel.class);
}
}
And registered it with Gson like Gson gson = new GsonBuilder().registerTypeHierarchyAdapter(DataObjectModel.class, new DataObjectDeserializer()).create();. But this didn't deserialize Museum model either.
The question is: how can I create a deserializer for parent class which would deserialize child class as well (as my second approach) Or How can I create a generic class with Gson so that every tyoe that is wrapped aroung data can be used with it like:
public class DataObjectDeserializer implements JsonDeserializer {
#Override
public T deserialize(JsonElement je, Type type, JsonDeserializationContext jdc)
throws JsonParseException {
// Get the "data" element from the parsed JSON
JsonElement data = je.getAsJsonObject().get("data");
// Deserialize it. You use a new instance of Gson to avoid infinite recursion
// to this deserializer
return new Gson().fromJson(data, /* This part not working due to type erasing in java*/ T.calss);
}
}

If you create your response and data structure like this
private class Data {
#SerializedName("name")
private String name;
#SerializedName("address")
private String address;
#SerializedName("lat")
private String lat;
#SerializedName("lng")
private String lng;
#SerializedName("phone")
private String phone;
}
private class Response {
#SerializedName("message")
private String message;
#SerializedName("status_code")
private int statusCode;
#SerializedName("data")
private Data data;
}
you can then do
Response response = new Gson().fromJson(json, Response.class);
if(response.statusCode == 0) {
//everything ok, do something with response.data
} else {
//display response.message, data will be null
}

GSON Deserializing Array of Custom Objects

I am trying to serialize/deserialize JSON in Android using GSON. I have two classes that look like this:
public class Session {
#SerializedName("name")
private String _name;
#SerializedName("users")
private ArrayList<User> _users = new ArrayList<User>();
}
and:
public class User {
#SerializedName("name")
private String _name;
#SerializedName("role")
private int _role;
}
I am using GSON for serializing/deserializing the data. I serialize like so:
Gson gson = new Gson();
String sessionJson = gson.toJson(session);
This will produce JSON that looks like this:
{
"name":"hi",
"users":
[{"name":"John","role":2}]
}
And I deserialize like so:
Gson gson = new Gson();
Session session = gson.fromJson(jsonString, Session.class);
I'm getting an error when I make this call.
DEBUG/dalvikvm(739): wrong object type: Ljava/util/LinkedList; Ljava/util/ArrayList;
WARN/System.err(739): java.lang.IllegalArgumentException: invalid value for field
I don't know what this error means. I don't see myself doing anything gravely wrong. Any help? Thanks!

Change your code to this:
public class Session {
#SerializedName("name")
private String _name;
#SerializedName("users")
private List<User> _users = new ArrayList<User>();
}
It's a good practice use Interfaces, and GSON requires that (at least, without extra configuration).
Gson converts the array "[ ]" in javascript, to a LinkedList object.
In your code, GSON tries to inject a LinkedList in the _users field, thinking than that field its a List.