NullPointer when getting response from REST using Retrofit

Question

I'm using Retrofit to comunicate with REST API on Android, but I getting an error NullPointerException like below. I try using postman, the API is work fine and I get the response.

java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.List ukmutilizer.project.com.ukm_utilizer.model.CheckEmail.getData()' on a null object reference

This my Activity class

private void sendRequest(String checkEmail){
    ApiInterface apiService =  ApiClient.getClient().create(ApiInterface.class);

    Call<CheckEmail> call = apiService.getEmailStatus(checkEmail);

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

            CheckEmailData emailDataList = response.body().getData();
            Log.d("Numer of Data : ", String.valueOf(response.body().getData()));

        }

        @Override
        public void onFailure(Call<CheckEmail> call, Throwable t) {
            Toast.makeText(CheckEmailPage.this, "Something went wrong!", Toast.LENGTH_SHORT).show();
            Log.e("Error Retrofit : ", String.valueOf(t));

        }
    });

this is the ApiInterface

public interface ApiInterface {
@POST("users/check_status")
Call<CheckEmail> getEmailStatus(@Body String email);
}

this is the retrofit instance

`public class ApiClient {

public static final String BASE_URL = "https://f49d9d29-8471-4126-95b0-1ec3d18eda94.mock.pstmn.io/v1/";
private static Retrofit retrofit = null;

public static Retrofit getClient(){

    HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
    logging.setLevel(HttpLoggingInterceptor.Level.BODY);
    OkHttpClient httpClient = new OkHttpClient.Builder().addInterceptor(logging).build();


    if(retrofit == null){
        retrofit = new Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build();
    }
    return retrofit;
   }
}`

and this is the json response

{
"code": 1000,
"message": "OK",
"data": {
    "id": "1",
    "email": "[email protected]",
    "status": "1",
    "name": "test",
    "category": "2"
  }
}

this is the POJO

`public class CheckEmail {


    @SerializedName("code")
    @Expose
    private Integer code;
    @SerializedName("message")
    @Expose
    private String message;
    @SerializedName("data")
    @Expose
    private CheckEmailData data;

    public Integer getCode() {
        return code;
    }

    public void setCode(Integer code) {
        this.code = code;
    }

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public CheckEmailData getData() {
        return data;
    }

    public void setData(CheckEmailData data) {
        this.data = data;
    }
}`

CheckEmailData POJO

`public class CheckEmailData {
@SerializedName("id")
@Expose
private String id;

@SerializedName("email")
@Expose
private String email;

@SerializedName("status")
@Expose
private String status;

@SerializedName("name")
@Expose
private String name;

@SerializedName("category")
@Expose
private String category;

public String getId() {
    return id;
}

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

public String getEmail() {
    return email;
}

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

public String getStatus() {
    return status;
}

public void setStatus(String status) {
    this.status = status;
}

public String getName() {
    return name;
}

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

public String getCategory() {
    return category;
}

public void setCategory(String category) {
    this.category = category;
}

}`

Possible duplicate of What is a NullPointerException, and how do I fix it? — Ken White
– Ken White, Commented Mar 10, 2018 at 1:49
@ahomphophone, I've been edit the question. Thanks in advance — rafitio
– rafitio, Commented Mar 10, 2018 at 2:05

Komang Sidhi Artha · Accepted Answer · 2018-03-10 02:14:10Z

1

You've got only one data, json object, from the api on the json response

{
"code": 1000,
"message": "OK",
"data": {
    "id": "1",
    "email": "[email protected]",
    "status": "1",
    "name": "test",
    "category": "2"
  }
}

yet you declare the data as a List object, where it expect the data above in a json array format.

you should change the List into

@SerializedName("data")
@Expose
private CheckEmailData data;

and I believe it would be fine.

answered Mar 10, 2018 at 2:14

Komang Sidhi Artha

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2 Comments

rafitio Over a year ago

Hi, I've been following your way, but the error still occurs.

Komang Sidhi Artha Over a year ago

can you post your change in your question?

ahomphophone · Accepted Answer · 2018-03-10 02:14:26Z

1

In that JSON, "data" is an object, not an array. In your CheckEmail class, change private List<CheckEmailData> data; to private CheckEmailData data;

answered Mar 10, 2018 at 2:14

ahomphophone

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2 Comments

Komang Sidhi Artha Over a year ago

I'm faster in 17 seconds :p

rafitio Over a year ago

Hi, I;ve been change my code and following your way, but the error still occurs

public void onResponse(Call<CheckEmail> call, Response<CheckEmail> response) {                  CheckEmailData emailDataList = response.body().getData();                 Log.d("Numer of Data : ", String.valueOf(response.body().getData()));              }

MatPag · Accepted Answer · 2018-03-10 02:16:45Z

Before accessing data in the response, you should check that the response itself is ok.

@Override
public void onResponse(Call<CheckEmail> call, Response<CheckEmail> response) {
    if(response.isSuccessfull()){
        //if you are sure that when the response is OK the list is not null
        //you can leave this line below to hide the lint warning, otherwise
        //before accessing the list with getData() check that response.body() is not null
        //noinspection ConstantConditions
        List<CheckEmailData> emailDataList = response.body().getData();
        Log.d("Numer of Data : ", String.valueOf(emailDataList.size()));
        for (CheckEmailData emailData : emailDataList){
            Log.d("Successfull : ", String.valueOf(emailData.getStatus()));
        }
    } else {
        //you got an error response, handle it
    }
}

rafitio · Accepted Answer · 2018-03-10 14:31:23Z

0

I've been solved the problem

I was add the headers on interface like below

public interface ApiInterface {
@Headers({
        "Content-Type:application/x-www-form-urlencoded"
})

@POST("v1/users/check_status")
Call<CheckEmail> getEmailStatus(@Body String email);
}

answered Mar 10, 2018 at 14:31

rafitio

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