HTTP POST request in java

Question

i'm a beginner with Java/Android and I have to do a http post request to a web-service to get keys (i post a date and i get keys).

import android.app.ProgressDialog;
import android.content.Context;
import android.os.AsyncTask;

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;

import javax.net.ssl.HttpsURLConnection;

public class HttpsPostRequest extends AsyncTask<Void, Void, String> {

    private Context context;
    private String content; //Body
    private String request;

    protected static ProgressDialog progressDialog = null;

    public HttpsPostRequest(Context context, String request, String content) {
        this.context = context;
        this.request = request;
        this.content = content;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        progressDialog = ProgressDialog.show(context, "Sending informations", "Please wait ...", false, false);
    }

    @Override
    protected String doInBackground(Void... voids) {
        InputStream inputStream = null;
        HttpsURLConnection urlConnection = null;
        StringBuffer json = null;
        try {

            URL url = new URL(request);
            urlConnection = (HttpsURLConnection) url.openConnection();
            urlConnection.setDoOutput(true); // indicates POST method
            urlConnection.setDoInput(true);
            urlConnection.setRequestMethod("POST");
            urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

            DataOutputStream dataOutputStream = new DataOutputStream(urlConnection.getOutputStream());
            dataOutputStream.writeBytes(content);
            dataOutputStream.flush();
            dataOutputStream.close();

            int reponse = urlConnection.getResponseCode();
            if (reponse != 200)
                return "Error";

            inputStream = urlConnection.getInputStream();
            if (inputStream == null)
                return "Error";

            InputStreamReader inputStreamReader = new InputStreamReader(inputStream, "UTF-8");
            BufferedReader reader = new BufferedReader(inputStreamReader);
            json = new StringBuffer();
            String line;

            while ((line = reader.readLine()) != null) {
                json.append(line);
                json.append("\n");
            }

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (urlConnection != null)
                urlConnection.disconnect();

            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException ignored) { }
            }
        }

        if (json == null)
            return "Error";

        if (new String(json).contains("{\"success\":true"))
            return new String(json);
        return "Error";
    }

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

The problem is the next, the server return the "GET" response of this request even if i say it's a "POST" and when i try to test my request with RESTClient it's return the good answer. So i need your help, did i forgot anything ?

Answer 1

Please remove below line

urlConnection.setDoInput(true);

In a GET request, the parameters are sent as part of the URL.

In a POST request, the parameters are sent as a body of the request, after the headers.

To do a POST with HttpURLConnection, you need to write the parameters to the connection after you have opened the connection.

This code should get you started: urlParameters would be your request.

byte[] postData       = urlParameters.getBytes( StandardCharsets.UTF_8 );
URL    url            = new URL( request );
HttpURLConnection conn= (HttpURLConnection) url.openConnection();           
conn.setDoOutput( true );
conn.setInstanceFollowRedirects( false );
conn.setRequestMethod( "POST" );
conn.setRequestProperty( "Content-Type", "application/x-www-form-urlencoded"); 
conn.setRequestProperty( "charset", "utf-8");
conn.setUseCaches( false );
try( DataOutputStream wr = new DataOutputStream( conn.getOutputStream())) {
   wr.write( postData );
}