play.api.data.format

val signedIntFormat = new Formatter[Int] {

 def bind(key: String, data: Map[String, String]) = {
   stringFormat.bind(key, data).flatMap { value =>
     scala.util.control.Exception.allCatch[Int]
       .either(java.lang.Integer.parseInt(value))
       .left.map(e => Seq(FormError(key, "error.signedNumber", Nil)))
   }
 }

 def unbind(key: String, value: Long) = Map(
   key -> ((if (value<0) "-" else "+") + value)
 )
}