Android로 Node.js 서버에 GET, POST 요청하기

Android MainActivity 부분

1. GET / 데이터 받기
public class MainActivity extends AppCompatActivity {

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

        tvData = (TextView)findViewById(R.id.textView);
        Button btn = (Button)findViewById(R.id.httpTest);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                new JSONTask().execute("http://192.168.25.16:3000/users");
            }
        });

    }

    public class JSONTask extends AsyncTask{

        @Override
        protected String doInBackground(String... urls) {
            try {
                JSONObject jsonObject = new JSONObject();
                jsonObject.accumulate("user_id", "androidTest");
                jsonObject.accumulate("name", "yun");

                HttpURLConnection con = null;
                BufferedReader reader = null;

                try{
                    //URL url = new URL("http://192.168.25.16:3000/users");
                    URL url = new URL(urls[0]);
                    con = (HttpURLConnection) url.openConnection();
                    con.connect();

                    InputStream stream = con.getInputStream();

                    reader = new BufferedReader(new InputStreamReader(stream));

                    StringBuffer buffer = new StringBuffer();

                    String line = "";
                    while((line = reader.readLine()) != null){
                        buffer.append(line);
                    }

                    return buffer.toString();

                } catch (MalformedURLException e){
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    if(con != null){
                        con.disconnect();
                    }
                    try {
                        if(reader != null){
                            reader.close();
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            tvData.setText(result);
        }
    }
}

2. POST / Body에 데이터 붙여 보내고 받기
public class MainActivity extends AppCompatActivity {

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

        tvData = (TextView)findViewById(R.id.textView);
        Button btn = (Button)findViewById(R.id.httpTest);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                new JSONTask().execute("http://192.168.25.16:3000/post");
            }
        });

    }

    public class JSONTask extends AsyncTask{

        @Override
        protected String doInBackground(String... urls) {
            try {
                JSONObject jsonObject = new JSONObject();
                jsonObject.accumulate("user_id", "androidTest");
                jsonObject.accumulate("name", "yun");

                HttpURLConnection con = null;
                BufferedReader reader = null;

                try{
                    //URL url = new URL("http://192.168.25.16:3000/users");
                    URL url = new URL(urls[0]);
                    con = (HttpURLConnection) url.openConnection();
                    con.setRequestMethod("POST");
                    con.setRequestProperty("Cache-Control", "no-cache");
                    con.setRequestProperty("Content-Type", "application/json");
                    con.setRequestProperty("Accept", "text/html");
                    con.setDoOutput(true);
                    con.setDoInput(true);
                    con.connect();

                    OutputStream outStream = con.getOutputStream();
                    BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(outStream));
                    writer.write(jsonObject.toString());
                    writer.flush();
                    writer.close();

                    InputStream stream = con.getInputStream();

                    reader = new BufferedReader(new InputStreamReader(stream));

                    StringBuffer buffer = new StringBuffer();

                    String line = "";
                    while((line = reader.readLine()) != null){
                        buffer.append(line);
                    }

                    return buffer.toString();

                } catch (MalformedURLException e){
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                    if(con != null){
                        con.disconnect();
                    }
                    try {
                        if(reader != null){
                            reader.close();
                        }
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            } catch (Exception e) {
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(String result) {
            super.onPostExecute(result);
            tvData.setText(result);
        }
    }
}

Node.js 부분

1. app.js
const express = require('express');
const app = express();

let users = [
  {
    id: 1,
    name: 'alice'
  },
  {
    id: 2,
    name: 'bek'
  },
  {
    id: 3,
    name: 'chris'
  }
]

 app.get('/users', (req, res) => {
   console.log('who get in here/users');
   res.json(users)
 });

 app.post('/post', (req, res) => {
   console.log('who get in here post /users');
   var inputData;

   req.on('data', (data) => {
     inputData = JSON.parse(data);
   });

   req.on('end', () => {
     console.log("user_id : "+inputData.user_id + " , name : "+inputData.name);
   });

   res.write("OK!");
   res.end();
 });

app.listen(3000, () => {
  console.log('Example app listening on port 3000!');
});

서버 통신을 구현하며 계속 FileNotFountException에러가 나서 하루동안 애를 먹었다.
스프링에서는 같은 url로 GET과 POST요청을 받아들였던 것 같은데 url 중복으로 생긴 문제였나보다.
url을 다르게 지정하니 문제가 해결되었다.