A Test project that uses Feign to upload Multipart files to a REST endpoint. Since Feign library does not support Multipart requests, I wrote a custom Encoder that enables this feature, using a HttpMessageConverter chain that mimics Spring's RestTemplate.

A few request types are supported at the moment:

• Simple upload requests: One MultipartFile alongwith some path/query parameters:

interface TestUpload {
    @RequestLine("POST /upload/{folder}")
    public UploadInfo upload(@Param("folder") String folder, @Param("file") MultipartFile file);
}

• Upload one file & object(s): One MultipartFile alongwith some path/query parameters and one or more JSON-encoded object(s):

interface TestUpload {
    @RequestLine("POST /upload/{folder}")
    public UploadInfo upload(@Param("folder") String folder, @Param("file") MultipartFile file, @Param("metadata") UploadMetadata metadata);
}

• Upload multiple files & objects: An array of MultipartFile alongwith some path/query parameters and one or more JSON-encoded object(s):

interface TestUpload {
    @RequestLine("POST /uploadArray/{folder}")
    public List<UploadInfo> uploadArray(@Param("folder") String folder, @Param("files") MultipartFile[] files, @Param("metadata") UploadMetadata metadata);
}

In order to build a Multipart file request I had to implement an in-memory version of MultipartFile. This is only for testing purpose, the best thing to do is to write another version that wraps a FileInputStream so you won't load all the file content in memory before uploading it.

Clone repo and build with maven. Launch ServerMain and then FeignClientMain.