@FormParam String unexpectedly throwing a 400 if omitted

[paharvey]

Using 6.2.5.Final, an endpoint which accepts multipart/form-data with two parameters like:

• @FormParam("password") String password
• @FormParam("file") InputStream stream

was returning an unexpected 400 if the String parameter is omitted in the request.

REPRODUCTION STEPS

Construct an endpoint as below, and then try submitting multipart form data of various combinations (each part could be omitted, be a file upload, or be plain form data).

import java.io.InputStream;
import jakarta.ws.rs.*;
import jakarta.ws.rs.core.*;

@Path("/")
public class MyEndpoint {
    @POST
    @Consumes(MediaType.MULTIPART_FORM_DATA)
    public void postWidget( //
            @FormParam("part1") String part1, //
            @FormParam("part2") InputStream part2, //
            @FormParam("part3") EntityPart part3) {
    }
}

I get an unexpected 400 for the following curl commands:

curl http://localhost -X POST -H 'Content-Type: multipart/form-data'
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=@file -F part2=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=@file -F part2=@file -F part3=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=@file -F part3=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part2=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part2=@file -F part3=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part3=@file

I get the expected 204 for the following curl commands:

curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=@file -F part2=@file -F part3=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=@file -F part2=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=@file -F part2=text -F part3=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=@file -F part2=text -F part3=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=@file -F part3=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=text -F part2=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=text -F part2=@file -F part3=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=text -F part2=@file -F part3=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=text -F part2=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=text -F part2=text -F part3=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=text -F part2=text -F part3=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=text -F part3=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part1=text -F part3=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part2=@file -F part3=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part2=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part2=text -F part3=@file
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part2=text -F part3=text
curl http://localhost -X POST -H 'Content-Type: multipart/form-data' -F part3=text 

WORKAROUND

To workaround, I have had to use EntityPart.getContent(String.class) to manually convert the provided form data into a String.

[jamezp]

What container are you running in? I recently added an example of using a multipart standalone application https://github.com/resteasy/resteasy-examples/tree/main/standalone-multipart.

[jamezp]

Okay cool, thank you. I'll have a look at this some time this week.

[jamezp]

Okay, this definitely looks like a bug. It's expecting the content type to be application/x-www-form-urlencoded. I'm not sure why it works when you leave the file name off yet, but it's definitely a bug :) I'll do some more debugging and file an issue about this and post it back here.

[jamezp]

JIRA https://issues.redhat.com/browse/RESTEASY-3390

[paharvey]

Thanks so much. That was a quick fix!

[jamezp]

No problem. I plan on back porting to 5.0 and 6.2 as well. I'll likely get to that tomorrow or Friday.