[JavaSpring/spring-cloud]@RequestParms should be used instead of @ RequestPart on file upload

Description

In SpringMVC, when do a form post with file upload, @RequestParms should be used instead of @RequestPart , see SpringMVC doc https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/bind/annotation/RequestPart.html

But now the generated file used RequestParms which would lead the OpenFeign initial with the wrong Encoder that file can't be transport as a binary

Swagger-codegen version

swagger-codegen-cli-2.3.1.jar

Swagger declaration file content or url

I reproduce with the petstore example.

https://petstore.swagger.io/v2/swagger.yaml

The form upload content is

/pet/{petId}/uploadImage:
    post:
      tags:
      - "pet"
      summary: "uploads an image"
      description: ""
      operationId: "uploadFile"
      consumes:
      - "multipart/form-data"
      produces:
      - "application/json"
      parameters:
      - name: "petId"
        in: "path"
        description: "ID of pet to update"
        required: true
        type: "integer"
        format: "int64"
      - name: "additionalMetadata"
        in: "formData"
        description: "Additional data to pass to server"
        required: false
        type: "string"
      - name: "file"
        in: "formData"
        description: "file to upload"
        required: false
        type: "file"
      responses:
        200:
          description: "successful operation"
          schema:
            $ref: "#/definitions/ApiResponse"
      security:
      - petstore_auth:
        - "write:pets"
        - "read:pets"

Command line used for generation

# download the stable release jar
wget http://central.maven.org/maven2/io/swagger/swagger-codegen-cli/2.3.1/swagger-codegen-cli-2.3.1.jar -O swagger-codegen-cli.jar
# run codegen with petstore
java -jar swagger-codegen-cli.jar generate -i http://petstore.swagger.io/v2/swagger.yaml -o gen -l spring --library spring-cloud

Steps to reproduce

view the generated gen/src/main/java/io/swagger/api/PetApi.java

see

@RequestMapping(value = "/pet/{petId}/uploadImage",
    produces = "application/json",
    consumes = "multipart/form-data",
    method = RequestMethod.POST)
ResponseEntity<ModelApiResponse> uploadFile(@ApiParam(value = "ID of pet to update",required=true) @PathVariable("petId") Long petId,@ApiParam(value = "Additional data to pass to server" ) @RequestParam(value="additionalMetadata", required=false)  String additionalMetadata,@ApiParam(value = "file detail") @RequestParam("file") MultipartFile file);

the @RequestParam("file") lead an encoder bug to the Feign, uploadFile won't work now.

Related issues/PRs

noop.

Suggest a fix/enhancement

In formParams.mustache , replace with

- ...{{#isFile}}@ApiParam(value = "file detail") @RequestParam("{{baseName}}") MultipartFile ...
+ ...{{#isFile}}@ApiParam(value = "file detail") @RequestPart("{{baseName}}") MultipartFile ...

Start with modules/swagger-codegen/src/main/resources/JavaSpring/libraries/spring-cloud/formParams.mustache and reproduce generation with the petstore Swagger file and spring-cloud library. Inspect the generated PetApi.java; done means file form parameters generate the annotation needed for binary upload rather than the current annotation that causes the Feign encoder issue.