Retrofit With Nested JSON Data (GET Method)

IMPORTANT POINT ::
1.In Retrofit library, Data parse according to POJO classes. If convertor is in GSON then convert your JSON to GSON POJO class.
2. If JSON is nested then multiple POJO Class is generate. In this app, Contact is array name and sub-array is Phone then 3 POJO Class will generate.
i. MainPojo - It is first class where all JSON array and sub-array listed and return POJO type value
ii. Contact - Json array, It's value can retrieve by MainPojo class.
iii. Phone - Json Sub-Array, It's value can retrieve by Contact POJO class.


STEP-1 : AndroidManifest.xml

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<uses-permission android:name="android.permission.INTERNET"/>

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STEP-2 : App level Gradle Library

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// retrofit, gsoncompile 'com.google.code.gson:gson:2.8.0'compile 'com.squareup.retrofit2:retrofit:2.3.0'compile 'com.squareup.retrofit2:converter-gson:2.0.2'

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STEP-3 :
ApiInterface.interface
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import retrofit2.Call;import retrofit2.http.GET;

public interface ApiInterface {

   @GET("/contacts/")
   Call<Movie> getTopRatedMovies();
}

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STEP-3 : ApiClient

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import retrofit2.Retrofit;import retrofit2.converter.gson.GsonConverterFactory;

public class ApiClient {

   // public static final String BASE_URL = "http://192.168.1.10";    public static final String BASE_URL = "http://api.androidhive.info";    private static Retrofit retrofit = null;
    public static Retrofit getClient() {
        if (retrofit==null) {
            retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();        }
        return retrofit;    }
}

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STEP-5 : MainActivity.java

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import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.widget.Toast;import java.util.List;import retrofit2.Call;import retrofit2.Callback;import retrofit2.Response;
public class MainActivity extends AppCompatActivity {

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);
        ApiInterface apiService =
                ApiClient.getClient().create(ApiInterface.class);

        apiService.getTopRatedMovies().enqueue(new Callback<Movie>() {
            @Override            public void onResponse(Call<Movie> call, Response<Movie> response) {

                if(response.isSuccessful()) {
                //  Toast.makeText(MainActivity.this, "OUTPUT : "+response.body().getContacts(), Toast.LENGTH_LONG).show();                    Log.d("MainActivity", "posts loaded from API");                 List<Contact> contactList =  response.body().getContacts();                    for(int i = 0; i<contactList.size(); i++)
                    {
                        int statusCode  = response.code();                        String id = contactList.get(i).getId();                        String name = contactList.get(i).getName();                        String email = contactList.get(i).getEmail();                        String address = contactList.get(i).getAddress();                        String gender = contactList.get(i).getGender();                        Phone phone = contactList.get(i).getPhone();                        String mobile = phone.getMobile();                        String home = phone.getHome();                        String office = phone.getOffice();                        Toast.makeText(MainActivity.this, "OUTPUT : "+statusCode +", "+ id +", "+ name +", "+ email +", "+ address +", "+ gender +", "+ mobile +", "+ home +", "+ office, Toast.LENGTH_LONG).show();                    }
                }else {
                    int statusCode  = response.code();                    // handle request errors depending on status code                }
            }

            @Override            public void onFailure(Call<Movie> call, Throwable t) {
                Log.d("MainActivity", "error loading from API");
            }
        });    
    }
}

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POJO CLASSES
STEP-6 : Movie.java   (POJO Class)
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   import com.google.gson.annotations.Expose;        import com.google.gson.annotations.SerializedName;
        import java.util.List;
public class Movie {

    @SerializedName("contacts")
    @Expose    private List<Contact> contacts = null;
    public List<Contact> getContacts() {
        return contacts;    }

    public void setContacts(List<Contact> contacts) {
        this.contacts = contacts;    }

}

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STEP-7 : Contact.java  (POJO Class)

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        import com.google.gson.annotations.Expose;        import com.google.gson.annotations.SerializedName;
public class Contact {

    @SerializedName("id")
    @Expose    private String id;    @SerializedName("name")
    @Expose    private String name;    @SerializedName("email")
    @Expose    private String email;    @SerializedName("address")
    @Expose    private String address;    @SerializedName("gender")
    @Expose    private String gender;    @SerializedName("phone")
    @Expose    private Phone phone;
    public String getId() {
        return id;    }

    public void setId(String id) {
        this.id = id;    }

    public String getName() {
        return name;    }

    public void setName(String name) {
        this.name = name;    }

    public String getEmail() {
        return email;    }

    public void setEmail(String email) {
        this.email = email;    }

    public String getAddress() {
        return address;    }

    public void setAddress(String address) {
        this.address = address;    }

    public String getGender() {
        return gender;    }

    public void setGender(String gender) {
        this.gender = gender;    }

    public Phone getPhone() {
        return phone;    }

    public void setPhone(Phone phone) {
        this.phone = phone;    }

}

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STEP -8 : Phone.java (POJO Class)

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import com.google.gson.annotations.Expose;import com.google.gson.annotations.SerializedName;
public class Phone {

    @SerializedName("mobile")
    @Expose    private String mobile;    @SerializedName("home")
    @Expose    private String home;    @SerializedName("office")
    @Expose    private String office;
    public String getMobile() {
        return mobile;    }

    public void setMobile(String mobile) {
        this.mobile = mobile;    }

    public String getHome() {
        return home;    }

    public void setHome(String home) {
        this.home = home;    }

    public String getOffice() {
        return office;    }

    public void setOffice(String office) {
        this.office = office;    }

}

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STEP-10, Finally JSON

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{
    "contacts": [
        {
                "id": "c200",
                "name": "Ravi Tamada",
                "email": "ravi@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "male",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c201",
                "name": "Johnny Depp",
                "email": "johnny_depp@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "male",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c202",
                "name": "Leonardo Dicaprio",
                "email": "leonardo_dicaprio@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "male",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c203",
                "name": "John Wayne",
                "email": "john_wayne@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "male",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c204",
                "name": "Angelina Jolie",
                "email": "angelina_jolie@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "female",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c205",
                "name": "Dido",
                "email": "dido@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "female",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c206",
                "name": "Adele",
                "email": "adele@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "female",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c207",
                "name": "Hugh Jackman",
                "email": "hugh_jackman@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "male",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c208",
                "name": "Will Smith",
                "email": "will_smith@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "male",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c209",
                "name": "Clint Eastwood",
                "email": "clint_eastwood@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "male",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c2010",
                "name": "Barack Obama",
                "email": "barack_obama@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "male",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c2011",
                "name": "Kate Winslet",
                "email": "kate_winslet@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "female",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        },
        {
                "id": "c2012",
                "name": "Eminem",
                "email": "eminem@gmail.com",
                "address": "xx-xx-xxxx,x - street, x - country",
                "gender" : "male",
                "phone": {
                    "mobile": "+91 0000000000",
                    "home": "00 000000",
                    "office": "00 000000"
                }
        }
    ]
}
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