Annotation Type Multipart
Marks a method as sending a
multipart/form-data body built from
its @Part/@PartMap-annotated parameters,
instead of the JSON/raw-string body a @Body parameter would
send. Valid only on
@POST, @PUT, @PATCH, and @DELETE methods -
using it on @GET, @HEAD, or @OPTIONS fails
validation, same as @Body. A method can't combine @Multipart
with a @Body parameter, and needs at least one @Part/
@PartMap parameter to be worth declaring multipart at all.
@POST("/users/{id}/avatar")
@Multipart
String uploadAvatar(@PathParam("id") String id, @Part("file") File avatar);