MultipartHttpMessageWriter()
Constructor with a default list of part writers (String and Resource).
MultipartHttpMessageWriter(partWriters: MutableList<HttpMessageWriter<*>>)
Constructor with explicit list of writers for serializing parts.
MultipartHttpMessageWriter(partWriters: MutableList<HttpMessageWriter<*>>, @Nullable formWriter: HttpMessageWriter<MultiValueMap<String, String>>)
Constructor with explicit list of writers for serializing parts and a writer for plain form data to fall back when no media type is specified and the actual map consists of String values only.
partWriters - the writers for serializing parts
formWriter - the fallback writer for form data, null by default