[JAVA] [Android] Uploading images from your device to the server

Introduction

I had trouble with the function to POST an image on Android and save it on the server, so I write it as my memorandum and output. I haven't worked on the program for half a year, so it may be strange, but please forgive me.

Postscript

I received your point. Thank you!

OkHTTP2 is treated as obsoletes. Make sure to use the latest 4.3.1.

https://square.github.io/okhttp/changelog_3x/#version-300-rc1 https://square.github.io/okhttp/changelog/

environment

I'm using OkHttp in Android Studio.

Introduced OkHttp

• Switch "Android" at the top left of the Android Studio screen to "Project".
• Open build.gradle in [app].
• In ~~ dependencies

implementation 'com.squareup.okhttp:okhttp:2.7.5'

#### **`Added.(2.7.Change 5 depending on the varsion.)~~`**

• Within dependencies `ʻimplementation'com.squareup.okhttp: okhttp: 4.3.1' Added ``. (Changed on January 24, 2020)

build.gradle

//～～ Omitted ～～
dependencies{
  //～～ Omitted ～～
  implementation 'com.squareup.okhttp:okhttp:4.3.1'//Postscript
}

Done.

AsyncTask Since it is sent by Http communication, it is done asynchronously.

OkHttpTask.java

import android.os.AsyncTask;
import android.util.Log;
import java.io.File;
import java.io.IOException;
import okhttp3.MediaType;
import okhttp3.MultipartBody;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;

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

    String responseBody;
    public HttpTask(){}

    @Override
    protected String doInBackground(String... params) {
        String url = "URL to send"; 
        MediaType media = MediaType.parse("multipart/form-data");
        try {
            File file = new File(params[0]);
            String FileName = file.getName();
            String boundary = String.valueOf(System.currentTimeMillis());

            RequestBody requestBody = new MultipartBody.Builder(boundary).setType(MultipartBody.FORM)
                    .addFormDataPart("file", FileName, RequestBody.create(media, file))
                    .build();

            Request request = new Request.Builder()
                    .url(url)
                    .post(requestBody)
                    .build();

            OkHttpClient client = new OkHttpClient();
            Response response = client.newCall(request).execute();
            responseBody = response.body().string();

            return responseBody;

        } catch (IOException e) {
            e.printStackTrace();
        }
        return responseBody;
    }

    @Override
    protected void onPostExecute(String result) {
        Log.d("a",result);
    }
}

I made a lot of changes, so I rewrote it. Also, with the change java.io.IOException: Cleartext HTTP traffic to example.com not permitted You may see an error like this. This is because HTTPS communication is used by default, so it is necessary to write a method to allow HTTP communication. Please see here for details on how to do this.

/**Delete
import com.squareup.okhttp.MediaType;
import com.squareup.okhttp.MultipartBuilder;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.RequestBody;
import com.squareup.okhttp.Response;
*/
import okhttp3.MediaType;
import okhttp3.MultipartBody;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.RequestBody;
import okhttp3.Response;

public class OkHttpTask extends AsyncTask<String, Void, String> {
  public OkHttpTask(){}

    @Override
    protected String doInBackground(String... params) {
        //URL of the post destination
        String url = "http://";
        File file = new File(params[0]);

        /**Delete
        *Set the content to POST here
        RequestBody requestBody = new MultipartBuilder()
                .type(MultipartBuilder.FORM)
                .addFormDataPart("file", file.getName(), RequestBody.create(MediaType.parse("image/jpg"), file))
                .build();
        */

        //Set the content to POST here(Change here)
        RequestBody requestBody = new MultipartBody.Builder()
                .addFormDataPart("file", file.getName(), RequestBody.create(MediaType.parse("image/jpg"), file))
                .build();


        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder()
                .url(url)
                .post(requestBody)
                .build();

        String result="";
        try {
            Response response = client.newCall(request).execute();
            if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
            {
                result = response.body().string();
            }
        } catch (Exception e) {}

        return result;
    }

    @Override
    protected void onPostExecute(String result) {
        Log.d("end:",result);
    }
}
*/

MainActivity.java

public class MainActivity extends AppCompatActivity {
  //URI of the image to send
  private Uri _imageUri;
  @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //Call here
        new OkHttpTask().execute(url);   
}

Recipient

Just save the posted file.

UpLoad.java

@WebServlet("/Upload")
@MultipartConfig(location = "Storage location")
public class upload extends HttpServlet {

	public void doPost(HttpServletRequest req,HttpServletResponse res) throws IOException, ServletException {
		String name="no_name";
		//multipart/form-Get all Part elements of this request provided by data
		for (Part part : req.getParts()) {
			//Get name
			for (String cd : part.getHeader("Content-Disposition").split(";")) {
				String str = cd.trim();
				if (str.startsWith("filename")) {
					String str2 = str.substring(cd.indexOf('=') + 1).trim().replace("\"", "");
					File f = new File(str2);
					name = f.getName();
					part.write(name);
				}
			}
		}
	}
}

Reference link

The story of using OkHttp for the first time https://qiita.com/LyricalMaestro0/items/698c77f5a964b5658bbb