multipart/form-data request is splitting up data field by field

Hello,

I’m using openapi-generator maven plugin to generate the client side java classes and interfaces for a third-party API. Generator version: 5.3.1 and FEIGN library to generate the client side.

API: requestBody: content: multipart/form-data: schema: $ref: '.domain#/components/schemas/Document' encoding: metadata: contentType: application/json style: form Domain: Document: type: object properties: metadata: $ref: '#/components/schemas/Metadata' document: type: string description: Array of bytes representing the content of the document format: binary

When I’m sending the request the metadata is split field by field instead of having it sent over as JSON.

` Content-Disposition: form-data; name=“validUntilRevoked” Content-Type: text/plain; charset=UTF-8

true Content-Disposition: form-data; name=“value” Content-Type: text/plain; charset=UTF-8

lorem ipsum Content-Disposition: form-data; name=“extRef” Content-Type: text/plain; charset=UTF-8

abc Content-Disposition: form-data; name=“issueDate” Content-Type: text/plain; charset=UTF-8 1992-10-12`

I’m expecting to be sent over in this format: `Content-Disposition: form-data; name=“metadata” Content-Type: text/plain; charset=UTF-8

{“evidenceType”:“<string>”,“ext_ref”:“<string>”,“issueDate”:“<string>”,“validUntilRevoked”:“<boolean>”} ` Do you have any idea if this is a bug on the openapi generatoror in the feign client?

Any suggestions will be appreciated.

Thanks!

[Breina]

You can’t set both content types myltipart to upload files and application/json to upload data in same request.

If it is not already supported, I feel like it should in any case:

Each part MAY have an (optional) “Content-Type” header field, which defaults to “text/plain”. If the contents of a file are to be sent, the file data SHOULD be labeled with an appropriate media type, if known, or “application/octet-stream”.

https://datatracker.ietf.org/doc/html/rfc7578#section-4.4

[bogdancondescu]

I found the way to solve it, modifying the encoder of Feign client and adding JsonFormWriter as first writer. apiClient.getFeignBuilder().encoder(new SpringFormEncoder() {{ var processor = (MultipartFormContentProcessor) getContentProcessor(ContentType.MULTIPART); processor.addFirstWriter(jsonFormWriter); processor.addFirstWriter(new SpringSingleMultipartFileWriter()); processor.addFirstWriter(new SpringManyMultipartFilesWriter()); }});