Using OkHttp3 to upload files in Multipart/Form-Data

Today I encountered an image upload interface. The backend access file is always null. If you look closely, it is ContentType: multipart/form-data. I don’t use much of this method, so I will record it here.

Preparation

First, make sure the project has added dependencies to the OkHttp3 library:

implementation '.okhttp3:okhttp:4.9.0'

ContentType Overview

ContentType, also known as media type or MIME type, is used to describe content types in network requests and responses.

Here are some common ContentTypes:

text/plain: Normal text
text/html: HTML Documentation
application/json: JSON data
application/xml: XML data
image/jpeg: JPEG Pictures
image/png:PNG Pictures
multipart/form-data: Used for file upload

This article focuses onmultipart/form-data, because it is often used for form submissions, especially forms containing file uploads.

step

1. Create MediaType

MediaType mediaType = ("image/jpeg");

MediaTypeFor description of file types, here we upload images in JPEG format.

2. Create a RequestBody

RequestBody fileBody = (mediaType, photoFile);

RequestBodyUsed to encapsulate file data to be uploaded.

3. Create a MultipartBody

RequestBody requestBody = new ()
        .setType()
        .addFormDataPart("file", (), fileBody)
        .build();

MultipartBodyFor building multi-part form requests, the file section is added here.

4. Add a request header

I don't know why he puts the parameters in the url...

Request request = new ()
        .url(":xxxxx/fileUploadAndDownload/upload?detailNo=1234&noSave=0")
        .addHeader("X-Token", token)
        .post(requestBody)
        .build();

Here we have added a custom request headerX-Token。

5. Send a request

OkHttpClient client = new OkHttpClient();
(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
        ();
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
        if (!()) {
            throw new IOException("Unexpected code " + response);
        }
        (().string());
    }
});

passOkHttpClientSend a request and process the response.

Complete code

Use OkHttp3 tomultipart/form-dataSample code for uploading images.

import okhttp3.*;

import ;
import ;
import ;
import ;

public class UploadImage {

    private static final String TAG = "UploadImage";

    public static void main(String[] args) {
        // Create MediaType        MediaType mediaType = ("image/jpeg");
        
        // Image file path        File photoFile = new File("path/to/your/");

        // Create RequestBody        RequestBody fileBody = (mediaType, photoFile);
        
        // Create MultipartBody        RequestBody requestBody = new ()
                .setType()
                .addFormDataPart("file", (), fileBody)
                .build();

        // Get custom request header        Map&lt;String, String&gt; headers = ().getHeaders();
        String token = ("X-Token");
        Set&lt;String&gt; keySet = ();
        for (String key : keySet) {
            (TAG, "uploadImage: " + (key));
        }

        // Create a Request        Request request = new ()
                .url("http://192.168.6.162:8888/fileUploadAndDownload/upload?detailNo=1234&amp;noSave=0")
                .addHeader("X-Token", token)
                .post(requestBody)
                .build();

        // Create OkHttpClient        OkHttpClient client = new OkHttpClient();

        // Send a request        (request).enqueue(new Callback() {
            @Override
            public void onFailure(Call call, IOException e) {
                ();
            }

            @Override
            public void onResponse(Call call, Response response) throws IOException {
                if (!()) {
                    throw new IOException("Unexpected code " + response);
                }
                // Process the response                (().string());
            }
        });
    }
}

I am using the EasyHttp library here. I don’t know how to set multipart/form-data, which causes EasyHttp to upload images.

That's why I used the native API to learn first. I'll post it here to upload pictures using multipart/form-data.

 		// Create a RequestBody, specify the media type and file        RequestBody fileRequestBody = (("image/jpeg"), photoFile);
        // Create, specify the field name and RequestBody         filePart = ("file", (), fileRequestBody);
        // Build MultipartBody        MultipartBody requestBody = new ()
                .setType()
                .addPart(filePart)
                .build();
        (this)
                .api(new UploadApi())
                .body(requestBody)
                .request(new OnUpdateListener&lt;Void&gt;() {
                    @Override
                    public void onUpdateProgressChange(int progress) {
                        (TAG, "onUpdateProgressChange: "+progress);
                    }

                    @Override
                    public void onUpdateSuccess(Void result) {
                        (TAG, "onUpdateSuccess:");
                    }

                    @Override
                    public void onUpdateFail(Throwable throwable) {
                        (TAG, "onUpdateFail:");
                    }
                });

Summarize

The above is personal experience. I hope you can give you a reference and I hope you can support me more.