springfox(swagger2) does not work with GsonHttpMessageConverterConfig

Question

What I am trying to build is a spring-boot (v1.2.3) application and expose my Rest API with SpringFox(swagger2) v2.0.0

my Swagger Spring config

@EnableSwagger2
@Configuration
public class SwaggerConfig {

    @Bean
    public Docket myApi() {
        return new Docket(DocumentationType.SWAGGER_2)
            .genericModelSubstitutes(DeferredResult.class)
            .useDefaultResponseMessages(false)
            .forCodeGeneration(false)
            .pathMapping("/my-prj");
    }

}

I need to use gson to convert my pojo's to json, and I do it this way:

@Configuration
public class GsonHttpMessageConverterConfig {

    @Bean
    public GsonHttpMessageConverter gsonHttpMessageConverter(Gson gson) {
        GsonHttpMessageConverter converter = new GsonHttpMessageConverter();
        converter.setGson(gson);
        return converter;
    }
}

The trouble is that if using GsonHttpMessageConverter, swagger v2 generates a wrong json:

{
"value": "{\"swagger\":\"2.0\",\"info\":{\"description\":\"Api Documentation\",\"version\":\"1.0\",\"title\":\"Api Documentation\",\"termsOfService\":\"urn:tos\",\"contact\":{\"name\":\"Contact Email\"},\"license\":{\"name\":\"Apache 2.0\",\"url\":\"http:
...

the JSON is prefixed with value and the real JSON becomes an escaped string.

here is how it should be if not using GsonHttpMessageConverter:

{
"swagger": "2.0",
"info": {
"description": "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a 
...

Is there a solution to create a correct swagger JSON without value and escaping?

Answer 1

This is Oleg Majewski's solution for SpringFox + Gson problem translated to Kotlin:

internal class SpringfoxJsonToGsonAdapter : JsonSerializer<Json> {

    override fun serialize(json: Json, type: Type, context: JsonSerializationContext): JsonElement
            = JsonParser().parse(json.value())

}

@Configuration
open class GsonHttpMessageConverterConfig {

    @Bean
    open fun gsonHttpMessageConverter(): GsonHttpMessageConverter {
        val converter = GsonHttpMessageConverter()
        converter.gson = gson()
        return converter
    }

    private fun gson(): Gson = GsonBuilder()
            .registerTypeAdapter(Json::class.java, SpringfoxJsonToGsonAdapter())
            .create()

}