[BUG] Broken Form @RequestPart should not be used for key-value property

[bademux]

Looks like passing formData with "application/x-www-form-urlencoded" never work.

As per documentation https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/bind/annotation/RequestPart.html @RequestParam should be used instead of @RequestPart if not file.
https://github.com/swagger-api/swagger-codegen/blob/master/modules/swagger-codegen/src/main/resources/JavaSpring/formParams.mustache

[cbornet]

Would you do a PR for this ?

[demtnt]

reproduce:

input.yaml
swagger: "2.0"
info:
version: 1.0.0
title: Example API
description: API
schemes:

• https
  host: example.org
  basePath: /swagger-spring-form

paths:
/application/email:
post:
summary: Lets a user to enter e-mail
consumes:
- application/x-www-form-urlencoded
parameters:
- name: email
in: formData
description: Email parametr
type: string
required: true
responses:
200:
description: Succesfully added e-mail`

build.gradle
`buildscript {
dependencies {
classpath('io.swagger:swagger-codegen:2.2.2')
}
repositories {
mavenCentral()
}
}
group 'org.example'
version '1.0-SNAPSHOT'

apply plugin: 'java'

sourceCompatibility = 1.8

repositories {
mavenCentral()
}

dependencies {
compile("io.springfox:springfox-swagger2:2.7.0")
compile("org.springframework.boot:spring-boot-starter-web:1.5.8.RELEASE")
}

import io.swagger.codegen.config.CodegenConfigurator
import io.swagger.codegen.DefaultGenerator

def swaggerSourceFileFull = "/$projectDir/specs/input.yaml"
def swaggerTargetFolder = 'src/main/java'
def apiPackage = 'org.example.api'
def modelPackage = 'org.example.model'

def configCommon = new CodegenConfigurator()
configCommon.setInputSpec(swaggerSourceFileFull)
configCommon.setOutputDir(projectDir.toString())
configCommon.setLang('spring')
configCommon.setApiPackage(apiPackage)
configCommon.setModelPackage(modelPackage)

configCommon.setAdditionalProperties([
'java8' : 'true',
'basePackage' : 'org.example.onboarding',
'configPackage' : 'org.example.swagger'
])

task generateApi {
doLast {
configCommon.addAdditionalProperty('interfaceOnly', 'true')
configCommon.addAdditionalProperty('sourceFolder', swaggerTargetFolder)
new DefaultGenerator().opts(configCommon.toClientOptInput()).generate()
}
}`

generated api:
`package org.example.api;

import io.swagger.annotations.*;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestPart;
@javax.annotation.Generated(value = "io.swagger.codegen.languages.SpringCodegen", date = "2017-10-30T10:17:18.750+02:00")

@Api(value = "application", description = "the application API")
public interface ApplicationApi {
@apioperation(value = "Lets a user to enter his e-mail", notes = "", response = Void.class, tags={ })
@ApiResponses(value = {
@apiresponse(code = 200, message = "Succesfully added e-mail param to {applicationId}", response = Void.class) })
@RequestMapping(value = "/application/email",
consumes = { "application/x-www-form-urlencoded" },
method = RequestMethod.POST)
default ResponseEntity applicationEmailPost(@ApiParam(value = "Email parametr", required=true ) @RequestPart(value="email", required=true) String email) {
// do some magic!
return new ResponseEntity(HttpStatus.OK);
}

}
`