Retrofit2 and converter-gson: Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $

Question

I have read previous solutions mostly this one for this problem but none of them worked for me. :(. While debugging i found raw request data from retrofit something like below picture and I've highlighted 2 portions:

here the 1st highlighted portion showing my retrofit request in raw json format

{
  "operation": "register",
  "studentModel": {
    "batch_id": "cseuui",
    "dept_code": "CSE",
    "password": "p",
    "student_address": "tpc",
    "student_email": "foc@gxs.bv",
    "student_id": "tyjvc",
    "student_name": "jak",
    "student_phone": "87532"
  }
}

but which giving me the 2nd highlighted portion of error:

Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $

But using postman i was able to successfully insert this raw json in the database.

{
  "operation": "register",
  "studentModel": {
    "batch_id": "cseuui",
    "dept_code": "CSE",
    "password": "p",
    "student_address": "tpc",
    "student_email": "foc@gxs.bv",
    "student_id": "tyjvc",
    "student_name": "jak",
    "student_phone": "87532"
  }
}

That means my server side is ok.
Is there any thing else i am missing?
I am giving some of my codes below,

Retrofit2 and Gson Dependency:

compile 'com.squareup.retrofit2:retrofit:2.1.0'  
compile 'com.squareup.retrofit2:converter-gson:2.1.0'

StudentModel.java

Server request and response

Retrofit Client and ApiInterface

and finally

Registration Method

as my server side is working perfectly with postman, what is the thing i am missing here. please let me know.

Answer 1

Create Model class Simple not list type.

after that create a String variable operation and Create Inner class of studentModel .

public class Main{

    @SerializeName("operation")
    private String operation;

    @SerializeName("StudentModel")
    private StudentModel studentModel;

}

and then generate getter setter

Answer 2

Finally I solved this problem, just by changing student model class variable names as my database column names, and i also removed @SerializedName("result") @Expose mapping in the class definition. Actually Database column names were not matching with my class variables. Thank you all, for your effort.

Answer 3

Try this:

Your reciving string instead of JsonObject.Change your ServerResponse like this mapping and add header as 'application/json'

1.Add headder header.put("Content-Type", "application/json");

private void registerProcess(String studentName, String studentAddress, String studentEmail, String studentPhone, String department, String batch_id, String student_id, String rePassword) {

        APIInterface appInterface = ApiClient.getClient().create(APIInterface.class);

        StudentModel student = new StudentModel();
        student.setStudent_name(studentName);
        student.setStudent_address(studentAddress);
        student.setStudent_email(studentEmail);
        student.setStudent_phone(studentPhone);
        student.setDept_code(department);
        student.setBatch_id(batch_id);
        student.setStudent_id(student_id);
        student.setPassword(rePassword);

        Log.e(TAG,student.toString());

        ServerRequest request = new ServerRequest();


        Map<String, String> header = new HashMap<>();
        header.put("Content-Type", "application/json");

        request.setOperation(Config_Ref.REGISTER_OPERATION);
        request.setStudentModel(student);

        Call<ServerResponse> response = appInterface.operation(request,header);

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

                if(response.isSuccessful()){

                    ServerResponse resp = response.body();
                    Toast.makeText(RegisterActivity.this, resp.getMessage()+" success", Toast.LENGTH_SHORT).show();
                    Log.e(TAG,resp.getMessage()+" success");
                }else{
                    Toast.makeText(RegisterActivity.this, response.message()+" not success", Toast.LENGTH_SHORT).show();
                    Log.e(TAG,response.message()+" not success");
                }
               /* Snackbar.make(fview, resp.getMessage(), Snackbar.LENGTH_LONG).show();*/

                //pDialog.dismiss();
            }

            @Override
            public void onFailure(Call<ServerResponse> call, Throwable t) {
                /*Snackbar.make(fview, t.getLocalizedMessage(), Snackbar.LENGTH_LONG).show();*/
                Toast.makeText(RegisterActivity.this, t.getLocalizedMessage()+" failed"+call.toString(), Toast.LENGTH_SHORT).show();

                Log.e(TAG,t.getLocalizedMessage()+" failed");
            }
        });


    }

2.ApiInterface.java

Add header as json format public interface ApiInterface {

    @POST("/iuk/api/credentials")
    Call<ServerResponse> operation(@Body ServerRequest request,@HeaderMap Map<String, String> header);
   }

3.ServerResponse.java

    public class ServerResponse {

    @SerializedName("result")
    @Expose
    private String result;
    @SerializedName("message")
    @Expose
    private String message;

    public String getResult() {
    return result;
    }

    public void setResult(String result) {
    this.result = result;
    }

    public String getMessage() {
    return message;
    }

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

    }

ApiClient.Java

public class ApiClient {

    private static final String BASE_URL = "https://xyz.000webhostapp.com";
    private static Retrofit retrofit = null;


    public static Retrofit getClient() {
        if (retrofit == null) {
            HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
            interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
            OkHttpClient client = new OkHttpClient.Builder().addInterceptor(new Interceptor() {
             @Override
            public Response intercept(Chain chain) throws IOException {
                Request.Builder requestBuilder = chain.request().newBuilder();
                requestBuilder.header("Content-Type", "application/json");
                return chain.proceed(requestBuilder.build());
               }
               })
                .connectTimeout(30, TimeUnit.MINUTES)
                .readTimeout(30, TimeUnit.MINUTES)
                .build();

            retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .client(client)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
        }
        return retrofit;
    }

}

Depedencies

compile 'com.squareup.retrofit2:retrofit:2.3.0'
compile 'com.google.code.gson:gson:2.8.2'
compile 'com.squareup.retrofit2:converter-gson:2.3.0'
compile 'com.squareup.okhttp3:okhttp:3.9.0'
compile 'com.squareup.okhttp3:logging-interceptor:3.9.0'    

Answer 4

you are trying to access array but Gson finds a string in the first line.

so you need to change the model class.

StudentModel.java

` public class StudentModel {

private String operation;
private Student student;

public Rootjava(String operation, Student student) {
    this.operation = operation;
    this.student = student;
}

public String getOperation() {
    return operation;
}

public void setOperation(String operation) {
    this.operation = operation;
}

public Student getStudent() {
    return student;
}

public void setStudent(Student student) {
    this.student = student;
}

@Override
public String toString() {
    return "studentModel{" +
            "operation='" + operation + '\'' +
            ", student=" + student +
            '}';
}

private class Student{
    @SerializedName("dept_code")
    private String deptCode;
    @SerializedName("student_name")
    private String studentName;
    private String password;
    @SerializedName("batch_id")
    private String batchId;
    @SerializedName("student_phone")
    private String studentPhone;
    @SerializedName("student_address")
    private String studentAddress;
    @SerializedName("student_id")
    private String studentId;
    @SerializedName("student_email")
    private String studentEmail;

    public Student(String deptCode, String studentName,
                   String password, String batchId,
                   String studentPhone, String studentAddress,
                   String studentId, String studentEmail) {
        this.deptCode = deptCode;
        this.studentName = studentName;
        this.password = password;
        this.batchId = batchId;
        this.studentPhone = studentPhone;
        this.studentAddress = studentAddress;
        this.studentId = studentId;
        this.studentEmail = studentEmail;
    }

    public String getDeptCode() {
        return deptCode;
    }

    public void setDeptCode(String deptCode) {
        this.deptCode = deptCode;
    }

    public String getStudentName() {
        return studentName;
    }

    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getBatchId() {
        return batchId;
    }

    public void setBatchId(String batchId) {
        this.batchId = batchId;
    }

    public String getStudentPhone() {
        return studentPhone;
    }

    public void setStudentPhone(String studentPhone) {
        this.studentPhone = studentPhone;
    }

    public String getStudentAddress() {
        return studentAddress;
    }

    public void setStudentAddress(String studentAddress) {
        this.studentAddress = studentAddress;
    }

    public String getStudentId() {
        return studentId;
    }

    public void setStudentId(String studentId) {
        this.studentId = studentId;
    }

    public String getStudentEmail() {
        return studentEmail;
    }

    public void setStudentEmail(String studentEmail) {
        this.studentEmail = studentEmail;
    }

    @Override
    public String toString() {
        return "Student{" +
                "deptCode='" + deptCode + '\'' +
                ", studentName='" + studentName + '\'' +
                ", password='" + password + '\'' +
                ", batchId='" + batchId + '\'' +
                ", studentPhone='" + studentPhone + '\'' +
                ", studentAddress='" + studentAddress + '\'' +
                ", studentId='" + studentId + '\'' +
                ", studentEmail='" + studentEmail + '\'' +
                '}';
    }
}

}`

Use this model class.

you can use the plugin to generate this POJO class.

Answer 5

Retrofit Getting InValid JSON Responce

try to Send Responce In this String Fromat from Server

         Gson gson = new Gson();
         response=gson.toJson(courseList);
         JsonObject myObj = new JsonObject();

         myObj.addProperty("operation", "register");

         myObj.add("studentModel",data);

         response = myObj.toString();

return responce;

Retrofit Builder

retrofit =new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();