gistfile1.java

@RpcObject(
    method = HttpRequest.Methods.POST,
    uri = "/post_image",
    requestSerializer = MultipartFormDataEncoder.class)
public class PostImage {

    // File name is set automatically and MIME type is determined by its extension
    @RequestBody public File image;

}

@RpcObject(
    method = HttpRequest.Methods.POST,
    uri = "/post_images",
    requestSerializer = MultipartFormDataEncoder.class)
public class PostMultipleImages {

    // Name is set to images[0], images[1], ...
    @RequestBody public List<File> images; 

}

@RpcObject(
    method = HttpRequest.Methods.POST,
    uri = "/post_something",
    requestSerializer = MultipartFormDataEncoder.class)
public class PostSomething {

    // Content-Type is set to application/octet-stream in this case
    @RequestBody public InputStream arbitraryData;

}