I use the MapBinder because depending on the value of the Console type ("novnc", "xvpvnc", "spice-html5", "rdp-html5"), we need to wrap the json object with different values ("os-getVNCConsole" when type is "novnc" or "xvpvnc", "os-getVNCConsole" when type is "spice-html5", and "os-getVNCConsole" when type is "rdp-html5". 

There are comments above, where @nacx recommends using a custom MapBinder, and I do not see a simpler way of accomplishing this.