Retrofit expected begin_object but was string at line 1 column 1 path $ 에러 해결

expected begin_object but was string at line 1 column 1 path $

expected a string but was begin_object at line 1 column 3 path $

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내가 작성한 data structure로 데이터가 expected begin_object but was string at line 1 column 1 path $ 뜨면서 안들어오니까 String으로 바꿔서 작업해봤지만 expected a string but was begin_object at line 1 column 3 path $에러코드가 뜨며 진전이 없었음.

원인은 List<>였음. List로 변경하니 잘 됨.

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예제코드 복붙

동작방식 : 가운데에 있는 Hello World! 텍스트를 누르면 레트로핏2로 통신해서 데이터가져온거 표시.

코드.

- 이전작업 gradle, internet permission, manifests application에 추가해주기(

  <application
        android:usesCleartextTraffic="true">


    </application>

일정 버젼 이상으로는 앱 통신시 http:// 주소로는 통신이 불가능하고 htttps://로만 통신이 가능하게 제약이 걸려있기 때문에 만약 사용하려는 api 주소가 http://면 해당 문구를 넣어줌으로서 접속이 가능하게 해주는 설정
1. MainActivity

package com.onsemiro.hanpinetree.chickeniot;

import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

import com.google.gson.JsonArray;

import java.io.IOException;
import java.util.List;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MainActivity extends AppCompatActivity {
    TextView retrofitTextView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        retrofitTextView = findViewById(R.id.retrofit_textview);

    //Retrofit 호출
        Call<List<ChickenDTO>> call = RetrofitClient.getApiService().postOverlapCheck();
        call.enqueue(new Callback<List<ChickenDTO>>() {
            @Override
            public void onResponse(Call<List<ChickenDTO>> call, Response<List<ChickenDTO>> response) {
                if(!response.isSuccessful()){
                    retrofitTextView.setText("연결이 비정상적 : "+ "error code : " + response.code());
                    return;
                }
                retrofitTextView.setText("연결이 성공적 : "+ response.body().toString());
            }
            @Override
            public void onFailure(Call<List<ChickenDTO>> call, Throwable t) {
                retrofitTextView.setText("연결실패"+ t.getMessage());
            }
        });

    }


}

2. activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/retrofit_textview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

3. RetrofitClient

package com.onsemiro.hanpinetree.chickeniot;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

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

public class RetrofitClient {
    private static final String BASE_URL = "http://내IP:8080/";

    public static RetrofitAPI getApiService(){return getInstance().create(RetrofitAPI.class);}

    private static Retrofit getInstance(){
        Gson gson = new GsonBuilder().setLenient().create();
        return new Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create(gson))
                .build();
    }
}

4.RetrofitAPI

package com.onsemiro.hanpinetree.chickeniot;

import java.util.List;

import retrofit2.Call;
import retrofit2.http.Body;
import retrofit2.http.Field;
import retrofit2.http.FormUrlEncoded;
import retrofit2.http.GET;
import retrofit2.http.POST;

public interface RetrofitAPI {

    @GET("aws/chicken/select")
    Call<List<ChickenDTO>> postOverlapCheck(); //이건 바디 요청시 사용하는거


}

5. ChickenDTO

package com.onsemiro.hanpinetree.chickeniot;

public class ChickenDTO {
    int no;
    int illumination;
    String time;

    public int getNo() {
        return no;
    }

    public void setNo(int no) {
        this.no = no;
    }

    public int getIllumination() {
        return illumination;
    }

    public void setIllumination(int illumination) {
        this.illumination = illumination;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    @Override
    public String toString() {
        return no+" "+illumination+" "+time;
    }
}

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ㅇ참고하면 좋은 레퍼런스
http://devflow.github.io/retrofit-kr/
https://morm.tistory.com/296