Upload a file to AWS S3 pre-signed URL using Retrofit2

Question

I\'m trying to upload a file to Amazon\'s S3 using a pre-signed URL. I get the URL from a server which generates the URL & sends it to me as part of a JSON object. I g

Answer 1

Use the following while uploading directly to S3 using presigned URL.

@Multipart
@PUT
@Headers("x-amz-acl:public-read")
Call<Void> uploadFile(@Url String url, @Header("Content-Type") String contentType, @Part MultipartBody.Part part);

Answer 2

With help from a colleague, this is the solution.

public interface UpdateImageInterface {
    @PUT
    Call<Void> updateImage(@Url String url, @Body RequestBody image);
}

Calling code:

    String CONTENT_IMAGE = "image/jpeg";

    File file = new File(localPhotoPath);    // create new file on device
    RequestBody requestFile = RequestBody.create(MediaType.parse(CONTENT_IMAGE), file);

    /* since the pre-signed URL from S3 contains a host, this dummy URL will
     * be replaced completely by the pre-signed URL.  (I'm using baseURl(String) here
     * but see baseUrl(okhttp3.HttpUrl) in Javadoc for how base URLs are handled
     */
    Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("http://www.dummy.com/")
        .build();

    UpdateImageInterface imageInterface = retrofit.create(UpdateImageInterface.class);
    // imageUrl is the String as received from AWS S3
    Call<Void> call = imageInterface.updateImage(imageUrl, requestFile);

Javadoc for info on @Url (class Url) & baseUrl() (class Retrofit.Builder)

MediaType is a class in the OkHttp library that is often used with Retrofit (both from Square). Info about constants passed to the parse method can be found in the Javadoc.