scala - Using SprayJson when json fields are optional -

i writing scala restful api , using sprayjson parse json being passed in during post call. example, have json structure looks this:

{"a", "b", "c", "d", "e", "f", "g", "h"} 

fields a, b, c , h required others not. have custom json formatter case class. various reasons, way need structure case class requires me custom json formatter.

here code snippet of read function in formatter:

def read(value: jsvalue) = {     value.asjsobject.getfields("a", "b", "c", "d", "e", "f", "g", "h")     case seq(jsstring(a),jsstring(b),jsstring(c),jsstring(d),jsstring(e),jsstring(f),jsstring(g),jsstring(h))     new object(a,b,c,d,e,f,g,h)     case _ => throw new deserializationexception("object expected") } 

how can implement above without having numerous case strings matching every possible permutation of fields may come in?

im not familiar spray-json, if not existed fields treated kind of jnull can try this:

implicit def jsvaluetostring(v: jsvalue): string = v match {   case jsstring(s) => s   case _ => null } ... case seq(jsstring(a),jsstring(b),jsstring(c), dopt, eopt,fopt,gopt,jsstring(h)) =>     new object(a,b,c,dopt,eopt,fopt,gopt,h)