[FIXED] Server receives the request body as null, when sending post request using okhttp. what could be the issue?

Issue

This is the Code which is sending the parameters fname selectedFile(byteArray) as part of the post request body from android to the tomcat server.

    public void uploadFile(){
        EditText filename=findViewById(R.id.fileName);
        //content://
        try {
            InputStream inputStream=getContentResolver().openInputStream(filePath);
            selectedFile= IOUtils.toByteArray(inputStream);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        String purl="http://192.168.1.11:8080/placement/V2TryUploadFile";

        RequestBody requestBody=new MultipartBody.Builder()
                .setType(MultipartBody.FORM)
                .addFormDataPart("fname",filename.getText().toString())
                .addFormDataPart("selectedFile",filename.getText().toString(),RequestBody.create(MediaType.parse("application/pdf"),selectedFile))
                .build();
        Request request=new Request.Builder()
                .url(purl)
                .post(requestBody)
                .build();

        Toast.makeText(MainActivity.this,filename.getText().toString(),Toast.LENGTH_SHORT).show();
        Toast.makeText(MainActivity.this,selectedFile.length+":",Toast.LENGTH_SHORT).show();
        OkHttpClient okHttpClient=new OkHttpClient();
        okHttpClient.newCall(request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                call.cancel();
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(MainActivity.this,"Failed to Upload",Toast.LENGTH_SHORT).show();
                    }
                });
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                final String responseString=response.body().string();
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Toast.makeText(MainActivity.this,responseString,Toast.LENGTH_SHORT).show();
                    }
                });
            }
        });

Servlet code (Running on tomcat server) to handle the post request sent from the android add

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        String fname=request.getParameter("fname")+".pdf";
        Part selectedFile=request.getPart("selectedFile");
        System.out.println(fname);
        System.out.println(selectedFile+"");
        InputStream filecontent = selectedFile.getInputStream();

        byte[] fileAsByteArray = IOUtils.toByteArray(filecontent);

        FileOutputStream imageOutFile = new FileOutputStream("C:\\Users\\VAISHAK`\\placeWorkSpace\\placement\\ResumeUploads\\" + fname);
        imageOutFile.write(fileAsByteArray);
        imageOutFile.close();
        doGet(request, response);
    }

The issue is fname and selectedFile are not shown null in android app , but both are shown as null in the tomcat server console.

Also Below is the tomcat server log in eclipse

null.pdf
null
Apr 13, 2020 11:56:20 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [trial.V2TryUploadFile] in context with path [/placement] threw exception
java.lang.NullPointerException
    at trial.V2TryUploadFile.doPost(V2TryUploadFile.java:49)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:688)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:615)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:818)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1623)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

Solution

I finally figured out the solution

The servlet by default does not handle

MutipartBody FORM

So in order for it to support that, we need to add the below annotataion to the servlet

@MultipartConfig

Answered By - karthik iyer
Answer Checked By - Timothy Miller (JavaFixing Admin)