How to configure Swagger UI, Jersey and file upload?

Question

I have a Jersey service with a file upload method that looks like this (simplified):

@POST
@Path("/{observationId : [a-zA-Z0-9_]+}/files")
@Produces({ MediaType.APPLICATION_JSON})
@Consumes(MediaType.MULTIPART_FORM_DATA)
@ApiOperation(
    value = "Add a file to an observation",
    notes = "Adds a file to an observation and returns a JSON representation of the uploaded file.",
    response = ObservationMediaFile.class
)
@ApiResponses({
    @ApiResponse(code = 404, message = "Observation not found. Invalid observation ID."),
    @ApiResponse(code = 406, message= "The media type of the uploaded file is not supported. Currently supported types are 'images/*' where '*' can be 'jpeg', 'gif', 'png' or 'tiff',")
})
public RestResponse<ObservationMediaFile> addFileToObservation(
    @PathParam("observationId") Long observationId,
    @FormDataParam("file") InputStream is,
    @FormDataParam("file") FormDataContentDisposition fileDetail,
    @FormDataParam("fileBodyPart") FormDataBodyPart body
){

    MediaType type = body.getMediaType();

    //Validate the media type of the uploaded file...
    if( /* validate it is an image */    ){
        throw new NotAcceptableException("Not an image. Get out.");
    }

    //do something with the content of the file
    try{
        byte[] bytes = IOUtils.toByteArray(is);
    }catch(IOException e){}

    //return response...
}

It works and I can test it successfully using Postman extension in Chrome.

However, Swagger sees 2 parameters named "file". Somehow it seems to understand that the InputStream parameter and the FormDataContentDisposition parameter are actually 2 parts of the same file parameter, but it fails to see that for the FormDataBodyPart parameter.

This is the Swagger JSON for the parameters :

parameters: [
{
  name: "observationId",
  required: true,
  type: "integer",
  format: "int64",
  paramType: "path",
  allowMultiple: false
},
{
  name: "file",
  required: false,
  type: "File",
  paramType: "body",
  allowMultiple: false
},
{
  name: "fileBodyPart",
  required: false,
  type: "FormDataBodyPart",
  paramType: "form",
  allowMultiple: false
}]

As a result, Swagger UI generates a file picker field, and an extra text field for the FormDataBodyPart argument :

So when I pick a file and submit the form in Swagger UI, I end up reading the content of the text field in the InputStream instead of the content of the uploaded file. And if I leave the textfield empty, I get the name of the file.

How can I instruct Swagger to ignore the FormDataBodyPart parameter ?

Alternatively, as a work-around, how can I obtain the media type of the uploaded file without the FormDataBodyPart object ?

I use Jersey 2.7 and swagger-jersey2-jaxrs_2.10 version 1.3.4.

Answer 1

Create a swagger filter for jersey and then mark the parameter as internal or some other string you are filtering on. This is also shown in this example:

https://github.com/wordnik/swagger-core/blob/master/samples/java-jaxrs/src/main/java/com/wordnik/swagger/sample/util/ApiAuthorizationFilterImpl.java

Your service method will have this parameter annotation

@ApiParam(access = "internal") @FormDataParam("file") FormDataBodyPart body,

Your filter will look for it like this:

public boolean isParamAllowed(Parameter parameter, Operation operation, ApiDescription api,
        Map<String, List<String>> params, Map<String, String> cookies, Map<String, List<String>> headers) {
    if ((parameter.paramAccess().isDefined() && parameter.paramAccess().get().equals("internal")))
        return false;
    else
        return true;
}

Register your swagger filter for jersey and then it will not return that field and swagger-ui will not show it which will fix your upload problem.

<init-param>
      <param-name>swagger.filter</param-name>
      <param-value>your.company.package.ApiAuthorizationFilterImpl</param-value>
    </init-param>