POST Request Method using JSON on Android

I need to do a POST request with a Webservice, where I pass a JSON with key and value as a parameter. This request is made on Android, when I make the request it returns me a JSON, with key values called ... ex: field1, field2, field3 ... I needed to create a method where I could pass as parameter in the call only the value of the search key:

Ex: In the POST method I pass:

{
    "select":"select id || ' | ' ||senha_terminal,nome,login_web,null,5,null n2,7,senha_terminal,senha_web,data_inclusao from usuario where id in (3257) order by id desc"
}

And as a return I have:

[
    {
        "campo1": "3257 | 74327",
        "campo2": "Sidnei",
        "campo3": "sidnei01",
        "campo4": null,
        "campo5": 5,
        "campo6": null,
        "campo7": 7,
        "campo8": "74327",
        "campo9": "56c07af798f309dbd75822a849ce47b6",
        "campo10": "2012-02-08T11:00:06"
    }
]

I would like to go to field1 and print on the screen.

The HttpService Class:

package com.example.romeu.cepteste;

import android.os.AsyncTask;

import com.google.gson.Gson;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.DataOutputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
import java.util.Scanner;

/**
 * Created by romeu on 28/02/18.
 */

public class HttpService extends AsyncTask<Void, Void, QueryDAO> {

    private final String query;
    StringBuilder resposta = new StringBuilder();

    public HttpService(String query) {
        this.query = query;
    }

    @Override
    protected QueryDAO doInBackground(Void... voids) {
        if(this.query != null)
        {
            //Realizar a consulta
            try
            {
                URL url = new URL("https://meuwebsite.com.br/");
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                connection.setRequestMethod("POST");
                connection.setRequestProperty("Content-type", "application/json");
                connection.setRequestProperty("Accept", "application/json");
                connection.setDoOutput(true);
                connection.setConnectTimeout(5000);
                connection.connect();

                JSONObject jsonObject = new JSONObject();
                jsonObject.put("select", "select id || ' | ' ||senha_terminal,nome,login_web,null,5,null n2,7,senha_terminal,senha_web,data_inclusao from usuario where id in (3257) order by id desc");

                DataOutputStream wr = new DataOutputStream(connection.getOutputStream());
                wr.writeBytes(jsonObject.toString());

                Scanner scanner = new Scanner(url.openStream());
                while (scanner.hasNext())
                {
                    resposta.append(scanner.next());
                }

            }
            catch (MalformedURLException e)
            {
                e.printStackTrace();
            }
            catch (ProtocolException e)
            {
                e.printStackTrace();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
        return new Gson().fromJson(resposta.toString(), QueryDAO.class);
    }

}

QueryDAO Class:

package com.example.romeu.cepteste;

/**
 * Created by romeu on 28/02/18.
 */

public class QueryDAO {
    public String campo1,campo2,campo3,campo4,campo5,campo6,campo7,campo8,campo9,campo10;

    //Getters

    public String getCampo1() {
        return campo1;
    }

    public void setCampo1(String campo1) {
        this.campo1 = campo1;
    }

    public String getCampo2() {
        return campo2;
    }

    public void setCampo2(String campo2) {
        this.campo2 = campo2;
    }

    public String getCampo3() {
        return campo3;
    }

    public void setCampo3(String campo3) {
        this.campo3 = campo3;
    }

    public String getCampo4() {
        return campo4;
    }

    public void setCampo4(String campo4) {
        this.campo4 = campo4;
    }

    public String getCampo5() {
        return campo5;
    }

    public void setCampo5(String campo5) {
        this.campo5 = campo5;
    }

    public String getCampo6() {
        return campo6;
    }

    public void setCampo6(String campo6) {
        this.campo6 = campo6;
    }

    public String getCampo7() {
        return campo7;
    }

    public void setCampo7(String campo7) {
        this.campo7 = campo7;
    }

    public String getCampo8() {
        return campo8;
    }

    public void setCampo8(String campo8) {
        this.campo8 = campo8;
    }

    public String getCampo9() {
        return campo9;
    }

    public void setCampo9(String campo9) {
        this.campo9 = campo9;
    }

    public String getCampo10() {
        return campo10;
    }

    public void setCampo10(String campo10) {
        this.campo10 = campo10;
    }


    //String para testes

    @Override
    public String toString() {
        return "QueryDAO{" +
                "campo1='" + campo1 + '\'' +
                ", campo2='" + campo2 + '\'' +
                ", campo3='" + campo3 + '\'' +
                ", campo4='" + campo4 + '\'' +
                ", campo5='" + campo5 + '\'' +
                ", campo6='" + campo6 + '\'' +
                ", campo7='" + campo7 + '\'' +
                ", campo8='" + campo8 + '\'' +
                ", campo9='" + campo9 + '\'' +
                ", campo10='" + campo10 + '\'' +
                '}';
    }
}

Main:

package com.example.romeu.cepteste;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

import org.w3c.dom.Text;

import java.util.concurrent.ExecutionException;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button btnConsultar = (Button) findViewById(R.id.btnConsultar);
        final TextView respostaTxt = (TextView) findViewById(R.id.respostaTxt);

        btnConsultar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v)
            {
                String query = "select id || ' | ' ||senha_terminal,nome,login_web,null,5,null n2,7,senha_terminal,senha_web,data_inclusao from usuario where id in (3257) order by id desc";
                try
                {
                    QueryDAO retorno = new HttpService(query).execute().get();
                    respostaTxt.setText(retorno.toString());
                }
                catch (InterruptedException e)
                {
                    e.printStackTrace();
                }
                catch (ExecutionException e)
                {
                    e.printStackTrace();
                }
            }
        });
    }
}

Where is the error that I can not answer?