What exactly are MultiPartEntity and Form Data? How are they used to upload images in android?

Question

I searched the web but i could only find code related to multipart form data, not explanation of what they are and how they are used?

Answer 1

Normally we are sending only string part of data,while in multipart file part is added with string ,so its called multipart.for example We can send multipart data using volley

 public class MultipartReq extends JsonObjectRequest {

        private static final String FILE_PART_NAME = "file";
        private static final String STRING_PART_NAME = "text";

        private final File mFilePart;
        //private final String mStringPart;


        MultipartEntityBuilder entityBuilder = MultipartEntityBuilder.create();
        HttpEntity httpEntity;
        Context context;

        private Map<String, String> params;
        public MultipartReq(Context context, int method, String url, JSONObject jsonRequest, Response.Listener<JSONObject> listener, Response.ErrorListener errorListener, File file, Map<String, String> params) {
            super(method, url, jsonRequest, listener, errorListener);

            this.context = context;
            mFilePart = file;
            entityBuilder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);    
            this.params = params;
            buildMultipartEntity();
            httpEntity = entityBuilder.build();

        }


        private void buildMultipartEntity() {

            try {
                if (mFilePart.exists()) { entityBuilder.addBinaryBody(FILE_PART_NAME, mFilePart, ContentType.create(mimeType), mFilePart.getName());

                    }
                    try {
                        if(!params.isEmpty()){
                            for (String key: params.keySet()){
                                 entityBuilder.addPart(key, new StringBody(params.get(key),ContentType.TEXT_PLAIN));

                            }
                        }
                    } catch (Exception e) {
                        VolleyLog.e("UnsupportedEncodingException");
                    }


                } else {
                    ShowLog.e("no such file");
                }
            } catch (Exception e) {
                ShowLog.e("UnsupportedEncodingException");
            }
        }

        @Override
        public Map<String, String> getHeaders() throws AuthFailureError {
            HashMap<String, String> params = new HashMap<String, String>();

            return params;
        }


        @Override
        public String getBodyContentType() {
            return httpEntity.getContentType().getValue();
        }

        @Override
        public byte[] getBody() {
            ByteArrayOutputStream bos = new ByteArrayOutputStream();
            try {
                httpEntity.writeTo(bos);
            } catch (IOException e) {
                VolleyLog.e("IOException writing to ByteArrayOutputStream");
            }
            return bos.toByteArray();
        }


        @Override
        protected void deliverResponse(JSONObject response) {
            super.deliverResponse(response);
        }
    }